Help me build an a20 with the flattest curve possible

[FyreDaug]

The exhaust is a pacesetter 4-2-1, 2" for the most part

Intake, some sort of custom manifold, havent worked it all out yet, but there will be a weber sitting on top. Was going to be a 36/36 but it may be too big for low end response.

Headwork: DIY port job, wont be too wild but too smooth things out for the most part. Exhaust will be ported more than intake. Would prefer to keep costs down by using a pre-made staged cam instead of a custom grind, so a stage 1 should be suitable. Ill get it decked at a machine shop and get a mild angle job

Compression is at an 87 motor right now, so im thinking if I get pistons ill go with 9.5-10, just getting the cylinders honed, with 20xxxxkm on motor a hone job may be equivalent to 20 over.

Bottom end: Pretty much stock, ill get new main bearings etc, but I imagine using stock rods/crank will be fine, maybe get them lightened a little.

Flywheel, just a lighterweight stock one, not much less weight.

Ignition: Some sort of MSD coil, will try out that quad coil mod I was thinking about, but im not expecting a whole lot from a theory.

What can I do to have a flat curve? Id rather have 120 across the board than 90 below 3000 and 150 above, you know what I mean?

[shepherd79]

you can't have 120hp all thought out the power band.
You can build up so the torque would stay as flat as possible, but without extensive dyno runs and testing you won't find out what work or not.
best thing is to build it up and dyno.
36 weber would be fine. you can port the stock intake to make it work.
prestaged cam, well no one makes them for our cars unless you want stock one. we can only get regrinds. get yourself lowest Delta cams grind (low and mid power) or delta 272 grind ( it is more for the midtop power). or you can get colt cam tryflow it should improve low, mid and high end.
If you port exhaust could possibly loose some torque numbers at low rpm.
your coil theory won't do much. just get yourself nice aftermarket single coil and stick with it.

if you look at A20 dyno chart you will see that A20 has very flat torque curve but horse power band starts small and goes up with RPM.

[FyreDaug]

Well I know I wont be able to get 120 across the band, I was using that for reference, that id rather have less but more all around than peak

[bobafett]

you will want an adjustable cam gear to dial in your cam timing to get the powerband where you want it. good luck finding one though.

[FyreDaug]

yeah I know

[cygnus x-1]

Check out my engine build thread over on Preludepower:

http://preludepower.com/forums/showthread.php?t=238337

It's got a parts list with prices. And there are some pictures of the headwork later on. You could do almost everything I'm doing without losing any torque. The only difference is that you might not want a Weber 38/38, the 32/36 would be fine. Use the stock A20 carbed intake with an adapter plate. A stock bottom end is fine, and with stock A20A3 pistons you get 9.3:1 compression. Everything else you list is fine.

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[A20A1]

Go with the 38, unless you are worried about milage then get the 32/36.

[FyreDaug]

Mileage is no concern, but would that hurt the bottom end a little? Having a 32 primary would help some torque right? What kinda numbers should I be looking at getting out of this motor? I havent paid any attention to A20 all motor builds

edit: but I dont want to dump alot of money into it, so I need to go for best bang for buck. Manifold will be custom and not included in these costs.

Should I bother boring it out a little if im going for new pistons anyways? Gain 2 extra lbs of torque that way.

Definately: Custom IM with weber 32/36 or 38/38. Pacesetter 2" mandrel exhaust with hooker muffler. New plugs/wires/cap/rotor/coil and a cam.

Cam im unsure of, because if I got a stage 2 cam and managed to get a timing gear I would see more gains than a stage 1 with stock gear, but then again whats the bang for buck here? stage 1 it seems.

If it turns out the motor isnt in the best condition with compression tests etc and it does need a rebuild, should I just hone them out, hope the pistons are still close to spec and put new rings in? If pistons need to be replaced, should I get stock 9.3 88-89 pistons? Or something aftermarket with a little bit more compression, upwards to 10? Which I may like better if I need to buy new pistons anyways. What about overboring? I wouldnt be able to do honing/boring myself, no equipment. So what about that?

(check out the kart progress thread, page 5 big updates)

[cygnus x-1]

Mileage is no concern, but would that hurt the bottom end a little? Having a 32 primary would help some torque right? What kinda numbers should I be looking at getting out of this motor? I havent paid any attention to A20 all motor builds

Actually I'm kinda curious about the 38/38 versus 32/36 thing as well. I found a fair deal on a 38/38 so I went for that. I thought I read that the 38/38 *might* be a little boggy at the low end but there isn't much data on it, so I can't stand by that statement. A20A1 would know better than I for sure so I'll believe him.
I'm aiming for 150HP at the crank for my build. Given the cam, carb, intake, head work, and header I think it's doable.

edit: but I dont want to dump alot of money into it, so I need to go for best bang for buck. Manifold will be custom and not included in these costs.

Got a line on a custom one eh? Go for it then! Post some pics when it's done.

Should I bother boring it out a little if im going for new pistons anyways? Gain 2 extra lbs of torque that way.

I wouldn't bore unless you have to. You will get small gains but not enough to really make much difference.

Definately: Custom IM with weber 32/36 or 38/38. Pacesetter 2" mandrel exhaust with hooker muffler. New plugs/wires/cap/rotor/coil and a cam. Cam im unsure of, because if I got a stage 2 cam and managed to get a timing gear I would see more gains than a stage 1 with stock gear, but then again whats the bang for buck here? stage 1 it seems.

I'm going with the stage 1 triflow from Colt. A stage 2 would be nice but I have emmissions testing to worry about. And I would rather have the lower powerband.

If it turns out the motor isnt in the best condition with compression tests etc and it does need a rebuild, should I just hone them out, hope the pistons are still close to spec and put new rings in? If pistons need to be replaced, should I get stock 9.3 88-89 pistons? Or something aftermarket with a little bit more compression, upwards to 10? Which I may like better if I need to buy new pistons anyways. What about overboring? I wouldnt be able to do honing/boring myself, no equipment. So what about that?
(check out the kart progress thread, page 5 big updates)

For cost reasons I went with the stock 88-89 FI pistons. Custom forged pistons are expensive and there is a long lead time. The bad thing though is that Honda doesn't seem to make much for oversize pistons. All I could find was a 0.3mm oversize, which is only like .012" over. My A20 block needed more boring than that so I used an A18 block and just had it bored to the stock 2.0L spec. The A18 and A20 blocks are otherwise identical.
So if your A20 is too far out of spec you might have to go for an overbore, which means you pretty much need custom forged pistons. As for overboring, just go as far as needed to get the bores straight and true.
Get a machine shop for the machining. They will know what to do.

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[A20A1]

This was a post about the 38
https://www.3geez.com/forum/showpost....22&postcount=9

[FyreDaug]

What did you pay for oem 88-89 FI pistons? That may be all I want to do. If its like double just to get 10 compression, im not gonan bother with that. Ill just put that money aside for nitrous later

[cygnus x-1]

Here is the build list so far:

A20A1 engine - ebay - $90
pistons (13102-PJ0-308 ) - hondapartsdeals.com - $175
rings - (sealed power E526KC) - Rock Auto - $76
wrist pins - hondapartsdeals.com - $40
rod/main bearings (Toga HP) - importperformanceparts.net - $95
thrust bearings
engine gasket kit (Felpro KS2404) - Rock Auto - $149
spark plugs (NGK 2115) - Rock Auto - $26
spark plug wires (Bosch 381-8065) - Rock Auto - $16
distributor rotor - hondapartsdeals.com - $4
distributor cap - hondapartsdeals.com - $16
ignition coil (accel ACC8140) - advanceautopars.com - $50
expansion plugs (sealed power 381-8065) - Rock Auto - $8
head bolts (ARP 218-4703) - importperformanceparts.net - $89
rod bolts (ARP 208-6001) - importperformanceparts.net - $36
oil pump (Toga OPH15-HV) - importperformanceparts.net - $89
water pump (Topline WPH17) - importperformanceparts.net - $32

valve rockers (1462[1/2]-PC6-600) - hondapartsdeals.com - $136
Timing Belt/tensioner (gates TCK160) - Rock Auto - $46

S&S Header - second hand - $220
Weber 38/38 - ebay - $170
Weber adapter plate - Carbs Unlimited - $65

clutch disk (4822Y30 yellow sprung organic) - clutchnet.com - $95
clutch plate (47615R47 red) - clutchnet.com - $178


Machine work:

degrease/inspect block - $58
bore/hone cylinders (1.8L to 2.0L) - $198
Final wash block - $48

crank balance - $99
polish crank - $58

lighten flywheel - $48
balance flywheel - $48

Install ARP rod bolts - $84

Install pistons on rods - $48

cam regrind

valve job - $296
port cleanup - DIY - Free

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[MessyHonda]

^^^ that sounds like a serious engine^^^ how much hp you think you will be puting down?

[cygnus x-1]

I'm not sure just what it will put out, but I would be happy with 150HP at the crank.

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[LiTtLe xOx BitT]

Did you already find a S&S header?? For the parts you have and $75 for the cam regrind your looking at like $2895, That doesnt include an exhaust (unless you already have one) or a ADJ cam gear. I found places that sell rebuilt motors for like $1000. Get a rebuilt A20 and turbo it, it will probably cost about the same but you will get more HP. You figure the A20A3 is 120 to the crank plus a turbo, exhaust, cam gear and cam regrind. I dont know about you but if i was going to spend $3000 i would definatly do a turbo.

[cygnus x-1]

All parts in that list I have, so yes I already have the header. You know, I never added up the total cost until now. $3000 is a bit more than I was expecting, but I guess it's a little late now! I'm sure a rebuilt engine could be had for $1000 but I expect that would include cheaper replacement parts. I could have cut a few corners as well but decided not to.

And who says I can't add a turbo later also? I know very little about turbos so I don't know what it would take to add one. I imagine I would have to switch to FI right?

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[bobafett]

hey that sounds like a great build up man!

[AccordEpicenter]

if you wanna go fast, go turbo! A20T>*

[DDRaptor]

Hey sounds like a great idea, like your idea, all i knew about modification was the cam grind and valves i got a long way to go.

Hey one of your links is dead. importperformance parts.com

i want to check out the pumps you got.

also may i suggest to get stainless steel lines for your coolant, etc.
i know your already spending plenty of cash.

[cygnus x-1]

Fixed the bad links, should have been "importperformanceparts.net"

Lots of hoses will likely be replaced when I put the engine back in. I'll look into stainless ones but will probably just go with plain to get it running.

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[DDRaptor]

bore/hone cylinders (1.8L to 2.0L) - $198

what does that mean the engine is already 2.0l do you mean that's the price to bore and rehone the cylinders?+

[cygnus x-1]

bore/hone cylinders (1.8L to 2.0L) - $198

what does that mean the engine is already 2.0l do you mean that's the price to bore and rehone the cylinders?+

Ahh, wondered if somebody would ask about that. The story:
The car is an '87 Prelude with a A18A1 (1.8L). When I decided to do a rebuild I picked up a cheap A20 on ebay to use as the core. But later I discovered that the A20 block needed a serious rebore, at least .020" over. That meant I couldn't use stock A20A3 pistons because they don't come that big. I could have gone for forged but the cost difference would be huge, considering that with forged pistons I would want to upgrade the rods as well. All the cheaper non-oem cast pistons have a large dish which makes the compression really low. So the best option was to have the A18 bored out to A20 specs. The A18 block is identical to the A20 except for bore size. Now I can use stock A20A3 pistons and maintain a 9.3:1 CR.

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[AccordEpicenter]

.020" is not that serious of an overbore, anything over .030" is ALOT. If you are gonna go custom pistons such as forged, overboring the stock size to .030" will cost you the same as a stock sized part. I believe you can get A20 pistons in some oversize varieties from honda but im not exactly sure what sizes are available or use some cheap aftermarket cast pistons

[FyreDaug]

Well since this thread was brought up again, I have another question. This is just thought too. Instead of building it for the flattest curve, what about getting the RPM to peak at lower rpms? I imagine a adj cam gear would help with that. But what cam to get then? Its kinda hard to explain how I want this motor to respond, but basically, if it comes down to sacrificing high end power for low end ill do it. After all, top end is gonna be covered by nitrous. So if I can shift it all down to have the most power around 3000 (just a number, I know it wont have peak power at 3k) and then use nitrous after that, itll give me a fairly flat response curve. But then again those cam gears seem a little difficult to get ahold of.

Ive decided to keep the exhaust 2" mandrel. header to 2.25" glasspack (little bigger so the gas can expand in there) then back to 2" to the hooker aerochamber muffler, then 2.5" tip.

Was initially going to be 2" with glasspack 2" then into 2.5" aerochamber and back to 2" for the tip, but the smaller I keep it all together the better torque I should have. Restriction wise shouldnt change much. The 2.5" and the 2" muffler flow ABOUT the same. But then again im not strapping a bottle to it right away, and even down the road a 50shot is more than enough. Putting me around 200hp

[DDRaptor]

if I'm correct paeco has a camshaft regrind that puts your power starting around 2500+, now if i can find that link.

here http://www.paeco.com/ you would have to download the manual unless you already have it.

but this is the excerpt.

"THis is a mild street Grind that is desiged to provide more torque and acceleration without being temperamental the best power range is 2500-6800 although it will rev to 7500
int: 27/59 Exh: 63/23 duration 266 life:.382deg
All cam regrinds $230 exchange (add 150 if no exhange)"