i'm pretty sure the dome volume for my pistons are 3.4cc
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i'm pretty sure the dome volume for my pistons are 3.4cc
Quote:
Originally Posted by hondalude86
Ok, so normally there is a dish on the piston tops, which means that the volume of the dish adds to the total combustion volume. That I would call a positive volume. With domed pistons the volume would then be negative because it subtracts from the total combustion volume.
The pistons you have are domed but they also have valve reliefs, so the net volume will either be positive or negative depending on whether there is more dome or more relief.
A positive volume (dish) of 3.4cc would give a CR of 9.6:1. A negative volume (dome) of 3.4cc would give a CR of 10.8:1. From the pictures it looks to me like there is more dome than relief, so I would say your CR is 10.8:1.
If the head has been milled at all that will bump up the CR even more. Figure roughly 1 extra compression point per 1mm remove from the head.
11:1 I think will be pushing the limits of pump gas unless you can supplement it with E85 or some other octane booster.
C|
Cool, this is on an a20 configuration or modded witht the 81mm bore sizing? Either way, it sounds like sounds like i need to skim the head to get it nice and true without trying to go big, if i am planning blow through turbo then i shouldnt get to crazy
E-85! Do work, son!!Quote:
Originally Posted by hondalude86
Quote:
Originally Posted by hondalude86
Yes, A20A3 is the baseline. 83mm bore, 91mm stroke, 1.27mm gasket thickness, 47cc nominal combustion chamber volume. The A18 and ET head chambers are a little smaller but I don't have any measurements for those. If anyone has a measured volume for an A18/ET head it would be helpful!
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got the head ready to be milled finally, and I got some pics too...
Btw, these are the exhuast ports...
http://i180.photobucket.com/albums/x...-59-29_859.jpg
rough cut...
http://i180.photobucket.com/albums/x...-52-23_140.jpg
a little bit smoother...
http://i180.photobucket.com/albums/x...-52-12_879.jpg
http://i180.photobucket.com/albums/x...-59-36_919.jpg
one of the few shots of the deep side...
http://i180.photobucket.com/albums/x...-02-40_612.jpg
smoothed out with 320grit...
I did buff the exhaust ports, but I didn't for the life of me remember to take pictures!!
Now the deshrouding on the exhaust side...
http://i180.photobucket.com/albums/x...-14-14_531.jpg
the amount that I want to take out...
http://i180.photobucket.com/albums/x...21-14-27_0.jpg
beginning...
http://i180.photobucket.com/albums/x...-14-34_895.jpg
http://i180.photobucket.com/albums/x...-14-40_558.jpg
more
http://i180.photobucket.com/albums/x...-38-57_543.jpg
not enough, so more!!!
http://i180.photobucket.com/albums/x...-54-58_535.jpg
enough?
Try not to get carried away matching the gasket as it's the bore you need to be inline with. also try and smooth out the edges around the machine edges where they cut into the chamber to put the seat in near the area where your opening up, and also try to use a smoother surface than the one you have currently. Valve seats aren't too recessed into the chamber roof so not much work needed there me being a perfectionist I'd still give them a little blending. Also you haven't altered the shape of the exhaust ramp at all, you can really help flow by making this area more aerodynamic like a sharks fin and you can reshape the guide end as well to suit. You can open up the exhaust ports quite a bit at least a few mm and definately more as you get nearer the manifold. Looks like you got bronze inserts in the exhaust guides have you got the same on the inlets as well? Hows the wear on the inserts is there much sideways play on the valve stems.
Also have the back of the valves backcut to match the seat width if this hasn't been done yet? Have you got a picture of the valves? inlet and exhaust.
Try and go over some of the photo's of my heads to give you some ideas and pointers.
I think you'll be quite shocked how much difference this will make even a basic head job with nice valve seats and matching backcuts creates a lot more flow.
Gave Benny a ride the other night in the silver lude with all it's full 200bhp think he was pretty shocked how quick it was!! lol!! But at least his lude gets to stay on the road now I have given him one of my spare boxes.
rich or hondalude: have you guys tried copper spray on the headgaskets yet? Ive been having similar issues with headgasket sealing on my car too and wanted to try it... Ive been following your build and its nice to see another A series build!
edit: Is deshrouding the valves really worth it with a bigger lift cam? I run 434" lift...
Same here.. we need a solution for headgaskets! I'm thinking of talking to cometic..
I have a copper sce but I really dont want to use it... Yours popped too eh?
I'm thinking that's all that happened to mine. I haven't touched it since it started acting funny. Been busy getting the crx up and running. I'm gonna hopefully pull the head off this weekend..
I use the copper spray on a felpro gasket, I havent had any trouble out of it.
I bought the indian head gasket sealer for head gaskets and am going to try it, unless people feel otherwise... got the head picked up and the valves lapped and installed. Maybe ill having running in time for the friday night meet.
I have an issue with mine as well now but it was down to the stupid test centre leaving the car running for ages without the fan running and it overheated and dumped all it's coolant out from the expansion tank was less than amused!! :0( Seems to be getting worse as well like yours loads of exhaust out of the breathers and smoking quite badly but that could be down to me not bothering to put on proper valve guide seals! lol! Still runs really well just smells and smoking like crap at the moment doh!
Yup rich, sounds like the beginning of a dark path that ive been on. Shoukd have the car running today provided the tstast housing seals good with out a tstat..
You know, not to be alarmist or anything, but someday Felpro is going to stop making the permatorque (blue stripe) head gaskets we like so much. They already don't make them anymore for the ET engines. An MLS gasket would be nice option for bigger NA and turbo builds.
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MLS groupbuy anyone??? I'd get like two sets..maybe three :D
We been down this route already though they'll only do copper which is real annoying!! And if they did stop them Ajusa ones are ok just have to change em every 5k miles! lol!
I wonder if anyone has done an A20 gasket in MLS before? If so then it's possible the dies are still around and more could be made.
Also, according to the Cometic website the thickness on a B18 gasket is 0.75mm, which is thinner than the normal Felpro gaskets (1.2mm). So that would bump up the compression about 0.5 points.
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Quote:
Originally Posted by rjudgey
Cometic will only do copper?
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Hey said MLS last time I talked to them...
Ok guys, got the car back together... Looking at a small break in period right now, but i'll give you guys an update!
http://i180.photobucket.com/albums/x...-26-20_330.jpg
picture of the head with the indian Head, head gasket shellac...
http://i180.photobucket.com/albums/x...-26-39_898.jpg
Block with the Shellac... new o ring in the oil control valve and I also replaced the o ring seal for the filter to block to stop the leaking. hahaha motor didn't leak at all except for having to reuse this oring before. no leaks now!!!
http://i180.photobucket.com/albums/x...-49-28_946.jpg
head back on! I torqued it to 20lbs, then 50lbs, 70, and then finally 95lbs...
http://i180.photobucket.com/albums/x...-03-12_767.jpg
intake and exhaust manifold back on... had a hard time with the intake manifold leaking, so i tried the shellac on the manifold... hope it truely works because it seems like it'd be terrible to clean off! hahaha
http://i180.photobucket.com/albums/x...-03-35_919.jpg
of course more classicprelude luv!
http://i180.photobucket.com/albums/x...-58-45_853.jpg
How I've been driving it the last couple of days...
http://i180.photobucket.com/albums/x...-58-58_149.jpg
http://i180.photobucket.com/albums/x...5-59-08_15.jpg
Fuckin' badass picture...
http://i180.photobucket.com/albums/x...-47-08_262.jpg
After about 15 mins of easy driving... about 45 degrees here in North Denver.
Per Richard's suggestion I'm no longer running a thermostat, so the temp stays pretty low under normal driving. The Hottest its been since i've gotten it running has been 170... I'm loving it!
I haven't really driven it very hard... been trying to keep it below 4k until i retorque it again. I will say that it seems pretty much the same, with the exception that its running smoother and much much cooler. I've had a couple blips up to 5500... feels pretty good. I'll retorque the headgasket wednesday or thursday, do a little ignition tuning and go to the dyno day on friday with hopefully better results.
furthermore... after much more thought... despite my power being in the 110whp range... I do expect to see in increase in high end power with the head gasket alone. That being said... 110lbs of torque here at 5300feet above sea level out of a 1.8 is pretty fuckin' badass. i'm excited about the potential here... EEEKKKK!!
Whens the dyno day? I'll go to dyno the crx :D
