10.5-or 11:1 comprestion

[2dsei]

goint to take my new head and get it planed 1o to 20 thousants and get it p&p get to compresstion up when i redo my engine how much do you think i can go with out the engine getting damanged

[A20A1]

well are you going to change your spark plugs... also are you getting any kind of engine (ignition/fuel) management?

I was thinking of doing 9.7:1 - 10.0:1

But rebuilding the engine isn't my thing.

[accordlxi2.0]

jesus 10.5:1

i'm sticking with my 9.6:1

[gfrg88]

isnt that guy versanick i think is his name running a b20 with 13:1 comp.???

[Deadhead]

I don't know, but i'd say if you have the money to go for higher compression, DO IT.

You get more power out of the motor and if you boost, you will get more hp for each pound of boost.

[b8er]

I don't know, but i'd say if you have the money to go for higher compression, DO IT.

You get more power out of the motor and if you boost, you will get more hp for each pound of boost.

i dont believe thats true, if you go boost you want low comp. high comp is for high reving all motor projects, im pretty sure once you start adding boost to high comp. your in for a BANG.

[2drSE-i]

yea high compression and boost can be run, but think about it. High compression off the bat, then add more pressure......pop like a balloon. like that google video, where the mustang blows the intake manifold off (lmao)

[b8er]

ah yes, i knew that hight comp. and boost was more prown to detination i just wasnt sure if its a streetable way to run boost, in my case i would much rater run low comp but i guess looking back at some dragserts we have had i feel like such a moron cause our last enginge was upwards of 11.5-1 running 20-25 psi boost, sorry guys, momentary laps of smartness ahah

[racerx]

if you want anything in the 10.0:1+ ratio range, you'll need to shave more then 0.010-0.020".

I would assume 0.030" would get you close to about 10.0:1, and you could probably safely go up to 0.035" and that would probably leave you at 10.5:1, but then again, why go that high if you're boosting?
you'll need all forged internals and a hella FM system to keep that thing under control. unless, of course, you want to rebuild it every 5000 miles... :)

[Hash_man_Se_i]

If you're going that high compression too, I would definately be rebuilding the bottom end too... Especially if its a high mileage motor, new bearings and such would definately be a good idea.

[AccordB20A]

ive just had head and block plained. not to increase compression but cause one was warped and the other had a narstey scratch. I really cant wait to see what this b20a of mine will perform like........

[Oldblueaccord]

goint to take my new head and get it planed 1o to 20 thousants and get it p&p get to compresstion up when i redo my engine how much do you think i can go with out the engine getting damanged

you will have to test assemble,mock up, the engine and check for piston to valve clearance. Most of the time clay in the piston and then check the thickness with mics. It would be debatable what clearance you would need. I would think .030 is ok but do some searches on some Honda specific sites for some more real numbers.

The other thing to remember is the timing belt will be come looser the more you shave off and I'm not sure how much the tensioner will take up.



There's a spec in the book for the max you cut from the head factory that is for a referance.

Also there is formulas that you can figure compression ratios with if you know all you dimensions. The cc of the conbusiton chambers would have to be measured since I never have found a "reliable " number on our head.


wp

[bobafett]

im curious what engine management u plan on using at 10.5 or 11:1

stock is 9.2 or 8.8 you are talking about a HUGE change in compression... tuning in a high compression motor is much more critical, so i hope you have a plan, other than just getting a high compression motor. :)

also worth mentioning is the fact that mike and daryl at openloop raised compression by welding inside the head, this would eliminate the need to shave or deck things as much. :)

[Ichiban]

Shaving the head and deck substantial amounts will retard cam timing as well. better have adjustable cam gear or some other way of compensating...

[w00tw00t111]

hey boba since the guys at open loop just welded inside the chamber, they wouldn't need to make any mods to the valvesprings or lifters right? One thing I was worried about was that if I decreased the squish area enough by a combo of hi comp pistons and skimming the deck/head that I would start getting some major valve lash. Just a question :)

[Ichiban]

do you mean valve lash or valve/piston interference? Valve lash won't be affected and any valve/piston interference means no-go. A20 valve lash is adjusted by a set screw on the rocker end, there are no lifters.

[bobafett]

^^ correct. but you are on the right track in assuming that increasing compression by welding the head will not affect head/block height and therefore not change the timing because of different dimensions. and your valvetrain should be unaffected by this mod

[88Accord-DX]

I'm new to this welding the head to raise compression, what & where is the welding at on the head?

[gfrg88]

yeah i have the same questions

[Ichiban]

some people call it a quench pad, on a 4 valve head it sorta resembles a cloverleaf, they fill the area around the edge of the chamber and between the valves.

[w00tw00t111]

Wow I feel pretty stupid. Oh well. So if you get a shop to P&P your head as well as increase the exhaust valve size and angle cut each valve would then welding the head make all the previous port work negligable? Why would welding the head be less safe then upping the compression ratio of the pistons? If I understand correctly upping the CR of the pistions is what causes the valve piston interference so if you are wanting to run 11-12.5 CR then wouldn't welding the head mean less headaches in getting the squish area at a safe level?

[w00tw00t111]

Well, besides the monetary objection I don't know why you wouldn't want to. I was talking to rjudgey and he explained to me that that's the aseries main limiting factor. That's where he found most of his power. And like I said if the shop wants in excess of 200 for each cylinder then unfortunetly I would have to go another route.

[bobafett]

yeah but we have 1 35mm exhaust valve per cylinder. and TWO 28?/33? mm intake valves. i think its fair to say we can get more air in than we can out...

again im not a flowbench master, but i thought i got the impression that exhaust side was restricting flow. :)

[bobafett]

thats true, we really cant FIT much bigger in there, but like ur sayin, there is plenty we can do to get that damn exhaust flowing

[bobafett]

oh yeah i knew that he had done it, also he mentioned that with lower CR and boost it would be a good idea to do that, and increase exhaust port size, so i guess i was on the right track for MY build, but definetly not for yours. :(

[w00tw00t111]

Here's a direct quote from one of the conversations I had w/ him

Hmmm bit hard this one really, i have a few different types of heads, ET,ET1,A18,A20,B20A, which one are you using, the best one i've used so far has been ET1 very good overall power and pulls hard to 7500rpm even with a mild spec camshaft and stock valves.

As with any head a nice clean up job, with some good 3 angle valve cuts on the seats and valves, chamber work, manifold and gasket matching, inlet manifold and header work on the inside, throttle body work, good CAI, mild camshaft, uprated injectors, regulator, pump, will all help and you should see a nice gain if you have a good exhaust and header.

But if you after something a bit more radical you need to start looking at bigger valves, if you have a B20A head you go go nuts here 2X 35mm inlet valves and 2X 30mm exhaust valves, which would be good for upto 250bhp. If you are running a A20 or any other 12 valve SOHC engine you can go upto 2X 33mm inlet valves and upto 38-39mm on the exhaust maybe 40mm at a push but may need a new seat. The trouble with the 12 vlave engine is the exhaust valve the fact that theirs only one!! As stock they are nicely matched espcially with some really good exhaust port work, you can make the port a bit bigger and also if you remove the guide end and ramp completely it will really free up the flow nicely, but if you don't you will bottleneck at 7000rpm, if you increase the flow into the inlet buy increasing the inlet valves to say 32mm-33mm without increasing the exhaust valve diameter you will run into the same problems again, this is what happened to my last big valve head, kept the exhaust valve same size and the inlets i went upto 33mm no matter what camshaft i used power died at 6K and at 7K it would just stop like a rev cut out!! But if you combine that with a fully ported and flowed port and a 38-40mm exhaust valve combined with a camshaft that opens and lifts the exhaust valve longer than inlet valve that should stop being a problem.

An A20 head with 2X33mm inlet valves and 1X 39mm exhaust valve with a camshaft of say 280 degree duration and 10mm lift on inlet side, and then 290 degree duration and 11.5mm lift or e.g Colt stage 3 would give you serious power with the right induction system, something like 45-48mm bore racing bike carbs or 45-50mm ITB Injection system would give you around 250bhp N/A would be a bit of a sod to drive in Traffic high rpm, rough idle and won't like pulling low down espcially with a lighter flywheel.

I won't go into it any further the port finish is dependant on what type of fuel system you use and the length of the inlet manifold, also the finish's i use on the valves and ports are what gives me the edge over anyone else, but the fact that most of the power gain is through the valve size and the type of fuel system you use, is you do all the above and then use stock inelt manifold or even Edelborck inlet manifold you'll never get more than 200bhp but if you go all out and get the biggest carbs you can or ITB's you can you will be looking at well over 200bhp. also if you are after 200bhp you will need a custom header and tube diameter of no smaller than 2.25" 2.5" to be on the safe side if you really wnat 250bhp or more.
Not trying to say you're wrong and for that matter since he does all the work himself it may be that getting a shop to do it is amazingly expensive BUT he has much much much more experience w/ Head work then anyone that I know of on this board so, I don't think it would be that bad of an idea to check in, or at least consider :)

[Ichiban]

not being really familiar with the A20 head i can't say for sure, but i would hesitate to upsize the valves right off the bat for reasons of shrouding. an example of this is the 20R/22R head/block combo. the 20R head flows better with smaller valves on the 22R block because of better ports and the valves are unshrouded when used with the larger 22R's bore. just something to think about.

[Oldblueaccord]

not being really familiar with the A20 head i can't say for sure, but i would hesitate to upsize the valves right off the bat for reasons of shrouding. an example of this is the 20R/22R head/block combo. the 20R head flows better with smaller valves on the 22R block because of better ports and the valves are unshrouded when used with the larger 22R's bore. just something to think about.

just to jump into the middle of this I think you can notch the bores to make the shrouding a little better on a 22 r. I know it helps like on my 318 when people run the 2.02 valve heads but good point none the less. I think also being our head is more hemisperical combustion chamber shape there's less of a shrouding problem.

Welding the heads combustion chamber changes the CC's of the chamber itself. http://www.btinternet.com/~mezporting/compression.html

mess with the calc a little espcially the CC # of the head. Just a few CC's makes a pretty good differance in compression.


wp

[Oldblueaccord]

yeah i have the same questions

http://www.theoldone.com/articles/b16a%5Fhead/index2.html

this isnt the pictures im thinking off but I thought endyn did chamber welding on there heads. good read none the less and great pictures.

wp

[2dsei]

got my head sent out and had it p&p only got it planed ten thousands and got a reground cam installed it sat big differance

[AccordEpicenter]

id run 10:1 on boost no hesitation. You na guys are pussies with that, go to 11.5:1 at least. My friend is running his NA LS/Vtec on PUMP GAS on a shitty tune with CTR pistons getting 12.6:1 CR and got 173whp on a Dyno Dynamics dyno (no pinging either, its all in the tune). If it was a dynojet and race gas it would be EASILY 200whp, all oem honda internals, stock head/cam/intake/tb... only thing he has is a cheapass header and cai. I still rape him all day long. Might not sound like much but i saw an H22A in a 01 type SH prelude made 179whp on a Dynojet (these typically read at least 10% higher) he had an aem cai, aem pullies, mugen header, dc sports exhaust and hi flow cat etc... There are reasons why openloop went through extreme measures to raise compression. If you took into account my turbo's boost and the engines stock compression, its like having a 15.63:1 compression (i run that on PUMP GAS) and on 13psi its more like 17.52:1. Thats how i make REAL power. Granted, you couldnt run 15:1 static compression on pump gas without detonating to kingdom come but you guys are really conservative. There are guys around boosting S2000's on pump gas and they already have 11:1 compression stock.

[racerx]

id run 10:1 on boost no hesitation. You na guys are pussies with that, go to 11.5:1 at least. My friend is running his NA LS/Vtec on PUMP GAS on a shitty tune with CTR pistons getting 12.6:1 CR and got 173whp on a Dyno Dynamics dyno (no pinging either, its all in the tune). If it was a dynojet and race gas it would be EASILY 200whp, all oem honda internals, stock head/cam/intake/tb... only thing he has is a cheapass header and cai. I still rape him all day long. Might not sound like much but i saw an H22A in a 01 type SH prelude made 179whp on a Dynojet (these typically read at least 10% higher) he had an aem cai, aem pullies, mugen header, dc sports exhaust and hi flow cat etc... There are reasons why openloop went through extreme measures to raise compression. If you took into account my turbo's boost and the engines stock compression, its like having a 15.63:1 compression (i run that on PUMP GAS) and on 13psi its more like 17.52:1. Thats how i make REAL power. Granted, you couldnt run 15:1 static compression on pump gas without detonating to kingdom come but you guys are really conservative. There are guys around boosting S2000's on pump gas and they already have 11:1 compression stock.

people who brag about shitty tunes and PUMP FUEL... :blah: maybe that's supposed to be cool, but it kinda seems :rice:

engines cannot take the kind of abuse people claim they can. sure, you'll get a few good runs at the track out of it, but keep going back every few months and you'll find you're getting a few tenths slower every time. i've seen it happen too many times. I got a friend who's runnin 11psi on a stock D16Y8 and he thinks it's a-ok because he's got an Apex SAFC. Of course his car gets slower all the time, but try tellin him that.

All I'm tryin to say is that if you wanna do something right, do it right the first time. Running on stock internals and 56psi with 3400cc injectors ain't cool; it's dumb. 11:1 compression on a stock NA is equally damaging. It's fun for a little bit, but for those of you who don't want to invest $2000+ on new internals every year or so, just build it first. (unless you're one of those hump em dump em guys who buys a different civic every year...)

The only reason people run pump gas on "built" engines is because they have no clue where to get real fuel (hello! the airport! 100 octane low lead), or they spent all their money on boosting the car. Please, if you wanna do things the smart way, be conservative with your compression and don't believe everything you hear about honda stock internals holding up to all sorts of abuse...

[rjudgey]

yep i agree most for fast road use 11:1, 12:1 for hardcore poeple and that would mean having to change head gasket every 15-20k as it will eventually blow it through the cylinders or into the coolant and thats even with a Felpro headgasket, unless you run a copper gasket but their a headache as well. Any higher your asking for trouble and will end up with cracked cylinder heads and melted pistons you will need forged if your running over 10.5:1 Cr ratio. Going upto 11:1 or little bit higher gives excellent gains any higher and you hit the laws of diminishing returns as well as shortening engine life hence why Honda only use 11:1 on S2000 as anymore and they know the engine won't last the warranty period.

[AccordEpicenter]

Yeah i do agree that it is harderi on parts, but racing in general is hard on parts. I know that pump gas isnt ideal or a great idea to do on high compression engine (or turbo), but if you run high octane (we usually get 3/4 tank of 93 or 94 and add 3-4 gal of 110 oct) there are significant gains to running 11.5:1 vs say 10:1 without serious engine longevity issues. Tell your friend that needs to get somthing to manage timing and get colder plugs, with the right setup/tune 11psi in a D16Y8 should last a long time. If your conservative with your ignition timing and AFR's you shouldnt be melting pistons and blowing headgaskets, thats caused by detonation and pinging.

[racerx]

pfff... he's probably running on 85 octane for all I know... thinkin it's cool to say that he's doing that...

if everything is perfectly tuned, with correct fuel and ignition timing, then yeah, 11psi will be ok for about 10,000 miles if he doesn't race it but once in a blue moon. (and if he NEVER redlines it)
but he likes to blow past the redline... it'll be toast in 3,000 miles tops.

[rjudgey]

The head gasket will still blow i know i change mine every 10-15k but having webers makes it real easy, drain coolant undo rad pipes, header, take off head bolts get beefy friend to lift up change headgasket sit back down, put bolts back in job done gotta love those teflon coated Felpro head gaskets so much easier not scrapping gasket of your block or head!! Nice and slick quickest time for HG yet is from start to finish is 2 hours.
The biggest problems i've found is with blowing between to cylinders thats not caused by Detonation thats caused by extreme pressure from tonnes of fuel and air going in getting squashed by piston that ignited High CR ratio makes that even worse it will eventually kill all head gaskets even copper ones after a while they just last longer, Felpro ones are best non copper gaskets and with a 12:1 will last 15-20k if your lucky racing half that figure. And thats from real experience use a Honda gasket or OEM patenet one you'll be changing every few thousand or worse soon as you plant your foot down bang your running on two cylinders and boy does that make a strange noise when one piston is firing into and another the other firing back it gets a bit funky allways manage to limp back home like that but gets difficult when idling as it tends to just stall so you have to keep revving it up as it's damn hard to start again on two!!

[rjudgey]

BTW anyone seen that new film the worlds fatest Indian that was just creepy i can just imagine myself being like that in another 30 years time still trying to squeeze the last bhp out of an old banger that should have been scrapped decades ago!! Shiver down my spine Good film though true as well!!

[racerx]

i haven't seen it, but i appreciate the input! sounds like a great film. it also sounds like you need to get better head gaskets... 15-20k miles is still pretty good, but you could invest in a 3-layer gasket if anyone makes em...

[AccordEpicenter]

thats a good idea... does anybody make a MLS style headgasket for an A20? What about having one custom fab? With Copper HG's dont you need to run o rings too or is that just a suggestion?

[rjudgey]

Yeah there's a company in U.K. called Ferriday engineering does some really cool custom stuff cheap does inlet manifold insulation gaskets where it keeps the inlet manifold cold it's a 5mm deep inlet gasket made of material that doesn't conduct heat and their only like £35 just need to send him a gasket to copy, and he also does Cooper Headgaskets with a patented combustion seal rings bit more expensive about £100 all in but worth it if you don't plan on re-building every 15-30k miles if i was looking for longeavity i would invest but i like blowing them up to see how i can improve on the next one that and i get Headgaskets from a Friend in the trade so their like £10 each!! So i don't mind changing them every 15-20k at that price.
Cometic will make them but your talking loads of money as they won't entertain just a single one off and even then their £100 odd each personally the copper ones would be just as good but the Felpro ones are pretty sturdy last one lasted 30k but the CR ratio on last engine wasn't very high 8.5:1 roughly. But when i boost that upto 10.5:1 or 11:1 should see a jump of about 20-25bhp alone hopefully!!

[bobafett]

gaskets are 65 ish a peice from cometic, and they have an a20 pattern now (or should, since i had a couple gaskets made custom) thats not a terrible price IMO

[AccordEpicenter]

copper, chris?

[bobafett]

yeah in custom gaskets they are only able to make copper, they cant/wont do MLS...

[Versanick]

It's to be noted that even with my high comp, I run a stock honda head gasket (usually for ease of finding, etc. i had the guy that did my bottom end search all over the place for my head gasket, and couldn't find a match anywhere for the life of him)... which isn't as nice as a well-made cometic or anything. but any steel-shim gasket is generally pretty durable.

Head gaskets don't like the high heat easily conducted from all directions in an aluminum block/head setup like the b20a. I use a 180 deg thermostat (I'm told that 160 is a bit too cold for EFI) and haven't had problems in 10,000 miles (and I drive this car H A R D).. but I also have hypereutectic pistons and cleaned up rods and ARP rod bolts. compression definitely will take a toll on your stock bottom end.

also, to confirm, I have HUGE gains running 93 octane plus octane booster (or when I put in 100) versus the (one time) I put in 87 to see what would happen. First, it wouldn't idle correctly. It ran rougher. And 5000-7000rpm felt like I was driving a b16 instead of a b20. seriously major difference. If you raise your compression past 10.5++ish, don't plan on using 85-87 octane anymore. Huge power difference, at least with MY compression.

Even if your pistons don't go above the deck, 11:1 compression will call for higher octane. Keep in mind gas prices when you're diving into this for your daily driver. Or keep in mind the 8hp gain just from paying more for the gas... good luck

[bobafett]

you can pick your thickness from a few sizes of copper sheet that they carry. my gasket is .050 thick, compressed, should be like .047 :)

[Versanick]

Remember, no matter how good your headgasket is, the wrong sort of misfiring and overheating can destroy it. Nothing's completely invincible. Gaskets, in some sense, are like light bulbs. Especially headgaskets. They could last 1 mile or 200,000. There is an average range, obviously, and taking better care of things (and proper installation) increases the life of the headgasket in most cases. Nothing wrong with going copper. I'll use OEM forever until (if) I boost.

Get a thin headgasket if you want. $65 is a good price for a copper job. It's certainly not a BAD decision to go for it. It's not like it costs 3x as much for the cometic. I'd do OEM. But others with great experience with copper HG's will advise you so. I think I'd find myself in a pickle here, since I know OEM is good, and I know via bobafett and others that these copper jobs are pretty solid, so I'd feel confident about either decision.

[Accordtheory]

how many of you guys experiencing failures with higher compression have tuned your setups on the dyno with aftermarket management or obd-1 and crome+ ostrich, or hondata, at least uberdata..? I don't understand why 11:1 compression is perceived as somehow unreliable, etc, when many new cars have compression in that area. In fact, I think that is the main reason for newer cars' better and better mpg. Toyota's celica gts has 11.5:1, for instance. (and dynos way over a gsr) Do you guys think that engine sacrifices reliability for that compression? No way. If I were to build an engine for n/a, I would go for around 13:1, or more. Yeah, peak cylinder press will be higher when driven hard, but will it be higher all the time? No. Same goes for boost. The thing is, with higher compression, you're burning less fuel to get the same press, hence the mpg improvement. And I wonder how much peak cylinder press will actually increase..maybe not as much as you would think, maybe that increased burn rate after tdc that requires less timing also puts the peak press into a more favorable crankshaft angle. And I saw at least one link to the endyn site in this thread, have you guys read the soft head 99 article? 23:1 static compression, and not a diesel!

I think if you build a high compression engine and then can't even get close to mbt without encountering knock on 91 octane, that is kind of pointless. I think pouring toulene into your tank would get kind of old after a while.. But if you can get up to mbt without encountering knock, then you're all good, but you still should have the j&s safeguard..
If you're running stock management with increased compression, your timing is probably past what is needed for maximum brake torque, and you're putting your engine in danger and making it fight itself unecessarily. Case in point, a buddy of mine had an ls vtec with ctr pistons with the distributor retarded, but not enough..he cracked half of his pistons..while I was running like 13psi on stock internals without piston/ring damage. (that time anyway..)Who do you think had higher cylinder press..?

[rjudgey]

If your cruising the pressure inside won't be as much as if running at high speed for one the throttle bodies aren't open fully so their not letting in portentially as much fuel and air so less to squish and also the rpms are less so it's getting less of a hammering per minute, if you doing 2500rpm as opposed to 8000rpm. Trust me i know i've blown enough headgaskets to know what works and what doesn't and how they go, they allways go when under hi load full throttle maximum rpm were not saying 11:1 is dangerous it's 12:1 or higher that you've got to be carefull off oem gasket or even any other aftermarket composite gasket including Felpro won't last long with more than 11:1 CR ratio 11:1 okay with Felpro for a while depending on how car is driven, but OEM Honda is the weakest i blow those things up so easy i don't bother buying anymore i use Ajusa which are tougher and tend to last 10k or more depending on how badly i'm treating the engine. If you want 12:1 or higher you'll need forged pistons probably uprated rods definately the bolts to ARP and you will need to deck both the head and block before even thinking about fitting copper head gasket then you need to make sure you either ring the block or have seals around the bores or it won't last five minutes under load. Their is a lot of preperation with Copper headgaskets they cannot just be dropped in like an OEM one can only be considered if your engine is at the re-build stage. If anyone want's a safe allrounder then just go Felpro with 10.5:1 upto 11.5:1 max you can go upto 12:1 maybe 13:1 but don't expect the Felpro to last much more than 5-10k miles at that kinda stress. P.S. with our engines i've found that with composite gasket it helps to retorque every 10-15k when used in racing enviroment makes gasket last a bit longer. Also recommend screwing down head bolts extra 5-10lbft as well helps keep the seal that bit tighter but again this is under race use all you road goign guy's with near enough stock engines ignore all of this unless you headgasket has never been re-torqued and it's starting to leak a bit then tighten it up a bit may help stop oil and water leakage.

[Accordtheory]

damn with those run on sentences!

[Accordtheory]

how many of you guys experiencing failures with higher compression have tuned your setups on the dyno with aftermarket management?
Well..? how about you, rjudjey?
..Someone should post up an a20 timing map tuned on the dyno for mbt for different levels of compression..
(not me)

[rjudgey]

Need an engine that works first.
In my experience it's not the igntion tuning that was the problem although it did take a while to realize the vac advance on the dizzy after converting to webers was melting the pistons as it was advancing way too much. The main problems is the gasket blowing out between cylinders which is a mechanical failure of the gasket rather than a tuning issue with Felpro this isn't too much of a problem but even with Quality Ajusa gasket this can happen 10-15k miles of hard driving with Stock Honda i've blown them by just putting my foot down for the first time take very little extra pressure. I'll say it again if anyone wants a new HG Felpro racing blues are the ones to get and if you do plan on running High CR ratio thats 12:1 or more then Custom copper is the way to go but needs to be prepped properly it can just be done by pulling off head and replacing stock needs to be done during re-build stage.

[AccordEpicenter]

what kind of prep is needed rich? I hear all kinds of conflicting info on that... My personal belief is that the reason why there are all kinds of guys around blowing up motors is that they are way too aggressive with ignition timing and just run into knock, thinking that as long as they have the correct AFS or way rich then theyll be ok...

[Lok]

For 2Dsei if he goes with Turbo set-up, I think stock US A20 C/R 8.8-9.3:1 (depends the version) is OK, just a save up ( for cleaning) 0.010 ( as he did) is the best.
Newer Turbo B16-B18C run 9-9.5:1 C/R even with 25-30 PSI but with race fuel.
With 1 Bar or 14.5 psi you can run easily 9.5:1 C/R with street fuel and a good mapped stand alone ECU ( obd-1 conversion) + larger injectors- tuned Fpr etc.

for N/A guys I think 0.030 would be OK....the C/R will go ~10.3:1 which is safe.
If you want more C/R like 11:1 or 12:1+ for more power, better solution will be forged custom pistons + wild cam+ p&p head etc.

Don't forget when you rise the C/R with shaved head, to give advance in cam timing (especially if you use and wilder cam than stock), so you will not have problem with dynamic C/R.. Check your ignition timing also.

[Accordtheory]

Need an engine that works first.
In my experience it's not the igntion tuning that was the problem although it did take a while to realize the vac advance on the dizzy after converting to webers was melting the pistons as it was advancing way too much.

..lol..I just have a feeling that if you tune for mbt, and there is still a margin of safety before encountering the knock threshold, you won't be blowing any headgaskets. And I still recommend the j&s safeguard, even if you think the margin of safety is enough, because you might get some lousy gas, and that thing will save your engine way before you would ever know anything was wrong..

And as far as pressure, I don't see how running 13 or so psi with a lot of other supporting upgrades (IM, 3" exhaust, etc) won't have higher peak cylinder pressure (obviously significantly higher average pressure) than a 12:1 or so n/a combo..and it takes a lot more than 13 psi, or around 220whp, to blow a stock head gasket.

And, when I blew my first engine, (rookie attitude + stupid electrical problem..broken ring lands) my stock headgasket was still ok..

I'll get some practice tuning my turbo b series hopefully not too far in the future..

[rjudgey]

it's definately not ignition tuning problem since i resolved the vac advance i.e removed i've never had knock problems since, and the car runs on very low ignition about 8-10 degrees is all it needs to produce full power in fact at higher advance it kills the top end power and produces less torque. With your headgaskets though how high was your engine revving too from the gaskets i've blown they all seem to go at very high revs and i know it's not a head or deck problem as each engine that's rebuilt has it's deck shaved and head skimmed. With my engines depending on what cam i'm using and what type of head ET, ET1, A18, A20 etc. the engines make anywhere between 180-210bhp the ET1 had stock size valves though but never had problem with the Felpro gaskets on their, only the A18 and ET which had 33mm inlet valves and wild cam 285 degree which would pull upto 8k although the later 33mm inlet A18 was resticted to 7k only due to piston fatigue, it was mainly at these revs that gasket would go don't drive the car normally doesn't get used as a daily driver just for track use and drag racing and at weekends when weather is nice.
I still think the stock gaskets are weak Felpro ones do the job nicely the engine allways die's before they need changing Ajusa seem to be good quality and as i can get them at £10 a piece i'm not that fussed that they blow up every 10-15k over the last 2 years i've seemed to have cured the piston fatigue issue by running a large piston to bore clearance .05mm more than Honda recommends but it does the job slaps it bit when cold starting but when warm is then silky smooth just pain in the arse having to get oversize rings and have to gap them all by hand to very tight tolerances.
Mind you just had a thought i was wondering that maybe the gasket problem could be related to not running the engine with a thermostat takes long time to warm up but when it is warm is about 1/4 on the gauge in summer unless it's very hot then maybe reach nearly half way, maybe i need to tighten the head more because of the colder engine temp come to think of it thats problem the cause of the gasket fatigue might try running with the thermostat back in again or try a plate in the housing.

[Accordtheory]

I doubt I have any advice to offer you, rjudgey, but a couple things you wrote make me wonder about what's going on with your setup..1st, when you cut down the deck of a block or the surface of a head, you're reducing the thickness of that metal, obviously, and I don't know how much you've removed, but maybe it's enough to allow the surface (s) to distort enough under pressure to lose the seal with the gasket..?
I read an interesting little article a while ago about coefficients of thermal expansion..it got into machine shops and how ambient temperature affects the size of the machined part, etc, then it walked the reader through a calculation of piston expansion vs. operating temp vs. cylinder wall/sleeve expansion.. So an engine is built to operate at a certain temp, if you lower the temp of the block but not the pistons, you need more piston/wall clearance. And if you boost a cold engine, the pistons can reach their full operating temp in a matter of seconds while the cylinders are still cold..an interference fit resulting in possibly a seized engine..
I don't think your thermostat is responsible for the gaskets blowing, but it surely contributes to your piston clearance issue..Why not keep all your clearances stable and run a thermostat?
I am amazed that you are only running 8-10 degrees of timing at high rpm. At atmospheric manifold press, a vtec b series runs about 28 degrees at anything over about 6500rpm.

[rjudgey]

The less ignition timing you use the better, the reason why it doesn't need any more advance timing is due to the mixture being very explosive due to the higher CR, and the fact that the headwork done mixes the fuel and air more efficiently, and also the ignition system being signicantly more power full than stock setup, it's not a wasted spark or anything fancy i just get a huge big fat mega spark, i don't deliberately use low igntion i just use what the engine wants to produce full power, when it's tuned on the dyno the timing is set to what ever produces the best power band and highest Bhp, normally run 95 octane fuel which is standard here 98 doesn't seem to make much difference.
Probably explain why after running more bore clearance i haven't had the same problems with pistons, as for the head and block being skimmed the block has minimal amount off just enough to flatten .25mm, the head no more than .5mm off although i have taken 1.5mm off before on a head that had about 6 skims in it's life but that never blew gaskets before just seems that since upgrading to 33mm inlet valves and putting down more power seems to have started being an issue although i've not had a chance to try Felpro gaskets as they set me back £45 pounds each and the Ajusa ones cost me £10 pounds (trade price know someone in parts distribution normally cost same as Felpro) Although Ajusa have changed the design recently maybe their new design is inferior although they don't seem to think so and it doesn't appear to be a poor part composite is very tough and the seal rings appear to be pretty solid. I think if i used Felpro on the larger inlet valves it will probably be okay.

[AccordEpicenter]

yeah i think there are tons of guys that are wayy to eager to run just a ton of advance and i think it just stresses parts. Youll be most likey to blow a headgasket from detonating than just getting your cylinder pressures too high from making power, as detonation makes your cylinder pressures go crazy

[Accordtheory]

i don't deliberately use low igntion i just use what the engine wants to produce full power, when it's tuned on the dyno the timing is set to what ever produces the best power band and highest Bhp
I'm just amazed that it's so low..I mean, shit, that's less than what a lot of turbo applications run at an atmosphere of boost!

..I think the last gasket I used was felpro..I don't remember though. I know the b series has a totally different style of gasket, it's just layers of metal stacked together..I don't know how that compares..

What about using arp or other aftermarket bolts and torqueing them to yield a a higher clamping force?

[Accordtheory]

I suspect the factory torque spec is more a limitation of the factory head bolts than anything else..not saying you could double the clamp load, just that there may be room for improvement.
what do you mean by warping/cracking due to higher heat output?

[rjudgey]

In my experience if you go too tight it can cause the seal rings to split but i normally do mine upto 60lbft and then after 10-15k re-torque again and sometimes upto 65-70lbft the bolts are strong enough especially A20A4 head bolts they are even thicker and have smooth shaft instead of that funny groove pattern, but thought about studing the block as the head bolts come out quite often it will wear out the bolt holes in the block, that way you could run any torque you want then.

Yeah i agree the ignition is strange it maybe camshaft related too, but thats what seems to work noramlly the camshaft timing is bout 0 or sometimes timed at -1 degree sometimes 2 have to be carefull though exhuast valve gets awefull close to piston so can't go much further than that advancing just seems to lower the peak powerband although does give good low end pull. Probably due to early experimentation of larger inlet valves and stock exhaust valve causing bottleneck so re-tarding the cam seemed to help.
Detonation never seemed to break the headgaskets funnily enough my pistons allwyas melted first and then eventually it causes stress fractures in the combustion chambers between the spark plug and valve seats and between the valve seats as well eventually going as far as the water jackets which then leads to pressurization of the radiator and hoses and explodes after a few miles letting out all your coolant!!! Not fun!!!

CKE with your build just run with the smallest amount of idle advance to make it tick over and pull away enough, also leave the vac advance tubes off the dizzy to stop it from advancing when crusing or idling that will help too, might be worth leaving it off completely to be on the safe side, in theory it should stop advancing when on full throttle but with a wilder cam the change in vacuum pressures can upset and make it do funny things thats what happened with my early engines, mechanic said i should run it and after 3 engine re-builds and a cracked head thought somethings not right and ever since i've not used the vac advance it's been perfect!!!

You should be fine with the 92ron octane with booster might be worth investing in a knock sensor if your really worried about, in a stock car it's easy to hear the knocking but on a car with Webers or loud exhaust and intake you can't hear it and after a few hundred miles your engine will be scrap and you'll have to start from scratch again!!

[rjudgey]

Come to think of it it's kinda handy having the head gasket go every 15k gives a me an excuse to de-coke the head and clean it all up again good for 5 bhp when put back together.

[Accordtheory]

CKE with your build just run with the smallest amount of idle advance to make it tick over and pull away enough, also leave the vac advance tubes off the dizzy to stop it from advancing when crusing or idling that will help too, might be worth leaving it off completely to be on the safe side, in theory it should stop advancing when on full throttle but with a wilder cam the change in vacuum pressures can upset and make it do funny things
There's a lot I don't understand here..you say you need less timing at high rpm, why didn't you modify (limit) the centrifugal advance, (I did that on one of my turbo setups) not the vacuum aspect? If you disable the vacuum advance, you just have a progressively increasing amount of advance with rpm until the centrifugal advance weights move to their limit.. so how much advance are you running at idle with the vacuum lines disabled?? I can't imagine that not making your car doggy as hell at part throttle/low manifold press..How do you know you're running 8-10 degrees at high rpm? I don't mean to contest you, but that still doesn't sound right to me. Did you hold a timing light on it when you ran it on the dyno? Or did you just lock out your advance altogether?

I say f the stock piece of shit distributor, do an obd-1 conversion and program the timing..

[Accordtheory]

I'm completely removing the stock ignition since I'm going OBD1, so I won't have to worry about 90% of the vacuum shit anymore =)
And thanks for calming my worries about blowing her up. I should get a daughterboard for the p75 so I can add knock detection.

obd-1 is definitely the way to go in my opinion, but I think you could probably loosen the distributor and retard the timing faster than the factory honda knock system could..seriously, you can hear knock before the system does anything about it, and by then, the damage is already done. Have you looked into the j&s safeguard?

[Accordtheory]

Eh, I ran without the vac advance for quite some time. Had a different feel throughout the range after I found the right timing setting for the setup at the time.
If you disconnect the vacuum advance, then you won't have enough timing for any part throttle driving, so then you advance the distributor, then you end up with too much timing at full throttle high rpm.

[rjudgey]

Don't forget 2G lude dizzy is different setup to 3G accord, i don't get any problems with mine and yes i do use a timing light to check the amount of advance but as i said ignition setup is not stock it's modified, but seems to work fine apart from being a bit inaccurate and yes a Megajolt system using twin coil packs would be much better but a the time it's up and running fine i'm happy when i'm trying to crack the 250bhp barrier i'll probably have to switch then.

[Accordtheory]

I just want to know how you know how much timing you're running at high rpm full throttle..

[Versanick]

Someone's going to grill me. My dizzy is advanced as far as it goes on the b20a (because Al set it up that way) and I don't get any problems.

I'm assuming I want to be ~15 at idle speed. My timing marks are hard to read though. I'tll be reset soon.

good luck

[speedpenguin]

Question:
Does porting the head always equal increased compression? Or does that just depend on exactly what you do to it?

[speedpenguin]

Oh ok.
I get it now.
So if I don't port inside the combustion chamber, I don't affect CR. I was a little confused... Thanks, I guess I really do learn something new every day. :)

[rjudgey]

unless you want to reduce compression for turbo then chamber work will drop CR ratio a little bit which would be cheaper than buying new pistons.
And as for Timing i don't klnow exactly what it would be , but the inside of the dizzy on mine is fixed so i know it's not advancing. 2G lude dizzy is very simple unlke later 3G accords ones, the ignition system isn't bad on the Carbed 2G ludes matched coil as standard good igntion module, but ultimately i want to put in a crank fired setup which i can dial in the amount of advance with a control knob or with laptop which will be far more accurate to get the most out of the engine without it exploding, so i do tend to run the least amount of ignition to make sure it doesn't explode, but doing this has revealed that the engine can make full power with an excellent powercurve and torque curve without needing massive amounts of ignition advance. I don't set it up with numbers i rolling road the engine with the best powercurve and figures, so i try the dizzy and the camshaft timing at all different settings which means a lot of dyno time but when you have a Friend who has a dyno you can afford to do that so i can really get the most out of the engine, or alternatively i use drag strip for live tuning and jetting to get the most out the engine as well. I'm constantly altering the settings as even a 5 degree change in temoperature will effect the optimun performance of the engine. It's hard work but with webers it's fairly simple procedure to be able to change the jetting if you have all the bits which i do.

[Ichiban]

a couple of quick questions here...

how are you setting your timing, at idle or higher? i know Mopar guys who all set their timing at 3000rpm so the centrifugal advance is already maxed out. this is supposed to accurately set timing at high rpm/WOT events where it is most critical,

how are you guys dealing with the timing change caused by head/deck milling? i didn't know there were adjustable timing gears for the A20...can you degree the cam and just skip a tooth on the timing belt if it brings the timing closer? come to think of it, as long as the timing marks are lined up on the gear/head, the cam timing should be fine, right?

finally, i've been looking around for hypereutectic or forged pistons for the A20 as well as better rods. i haven't found much. suggestions? has anyone shot peened and stress relieved their factory rods? are they good? do they suck?

edit: CKE, we should tee up on this, i'm planning a NA build in the same direction as yours..

[rjudgey]

Teg LS rods fit but you need to have custom pistons made with a 21mm wrist pin size, as far as the timing goes i'll check it out next time i'm at the dyno, The camshaft timing is a doddle don't adjust using the belt thats like 10 degrees at a time, when you skim the ehad it only puts it out a couple of degrees, it doens't make much difference, but if you want to play you have to file out a bigger groove on the cam pulley then get various guauges of steel wire or metal shims about 1.5mm long and use that to fit inbetween the pulley groove and the cam key this will alter the amount of advance and retard on the cam pulley, it's a bit ghetto but it works it's been used by engine builders for decades, the other option is to make up your own set off offset key ways for the camshaft but thats a lot of grief with a file and if not strong enough can cause severe failure.

[Ichiban]

can a20 pistons be machined out? i may be becoming a machinist in the near future...i suppose i could custom order pistons to the exact specs but $$$$.