I currently have a crvtec setup using 85mm 11:5:1 JE pistons. At first I was planning on using my LS head, however I changed my mind and went with a 95 GSR head. Since the GSR has smaller combustion chambers my cr is 12:5:1. What size headgasket do I need to lower it to 11:5:1? Or would it be better to open the GSR combustion chambers to LS spec? I am currently using a cometic .062 headgasket but I am still pinging like crazy! I also increased my fp to 50and retarded my timing 2 degrees but the car still pings....What should I do?

 

I feel for you man. You can

-de-burr your pistons so they have dull edges
-open up the chamber sides a to match the bore. This will help lower the compression and make the chamber shape more combustion friendly.
-running tighter deck will help deter detonation but also raises compression. Using a 0.040 head gasket will help combustion dynamics.

Here is a pic of Endyn's pistons with nice dull radiused edges and a satiny finish.



[Modified by Rocket, 8:02 PM 5/1/2002]

 

the combustion chamber in the GSR head is 40 and the LS is 42?? Is that correct? So if I open the combustion chambers to 42, then with the stock headgasket wouldn't my cr be 11:5:1? This pistons were designed to give a 11:5:1 with the LS head. Will opening up the GSR combustion chambers also increase HP output as well? Much thanks for the info, I am getting nervous about detonating, whatever I do, I need to do it ASAP

 

I am not sure if you can get 2cc's by opening up the sides but it should help a whole lot.

Yeah, detonation is for shitty old Toyotas (clak, clak, clak, clak, ) but not for high performance Honda's.

 

LS combustion chambers are 45cc, GSR are 41.6cc.

Do you know what your piston dome displacement is? For Arias 11.5:1 LS pistons it's 6.1cc, but they don't have any B20 applications listed on their site so I don't know the spec. I'll just assume it's the same.

So, according to http://www.c-speedracing.com/howto/c.../compcalc.html your CR is 11.18:1.

[edit] That's with your headgasket figured into the mix. With an OEM headgasket you'd be at 12.26:1.

[edit again] OEM headgasket is 0.029" thick.

[edit yet again] I'm stupid, I have no clue why I thought you said Arias pistons.

[Modified by MrFatBooty, 9:04 PM 5/1/2002]


[Modified by MrFatBooty, 9:05 PM 5/1/2002]


[Modified by MrFatBooty, 9:06 PM 5/1/2002]

 

So yeah, if you know the dome displacement of your pistons you can plug it and the headgasket thickness into that handy dandy link I provided amidst my stupidity and figure out what the hell your CR is exactly.

 

for now retard timing all the way and if it still pings run race gas. i know its a lot of money but it sux to **** up your motor.

 

i say take the head to a good head porter and have them open up the chambers and make them larger.......if you can drop the CR just under 12:1 i'm sure you will be fine......

here's my head with 84.5mm chambers. (46.2cc)

 

Well i just did a little research on my JE pistons and all I can say is CRAP!!!!!!!!

My dome CC=4.8cc
Head is slightly milled .010 so my head cc is roughly= 39cc
bore=85
stroke=89

with stock headgasket I am fricking nearly 13:5:1!!!!!!!!!!!! No wonder I was pinging like crazy on pump gas!!

I can get near 11:5:1 if I just slap on a .067 headgasket. Can a good porter go from 39 to 45cc on the head?? Or is this too much for the combustion chamber?.
If I can take the chambers to 45 then all I need is .029 headgasket to be at 11:7:1

 

sell the GS-R head and get a B16 head?

but a good head porter can probably take the square shape of the GS-R head chamber and make it round like the LS and B16 head.

ask a few good hear porters and see what they say........

 

non-VTEC, is that head on your motor yet? It looks nice, what type of motor are you building again, and is it installed yet?

 

yes thats the head on my engine......

these are my rods:


my pistons:


my valve train components:



that's enough pics for now........more details later......

 

What are you using to compute your CR values? I put this stuff into the calculator I'm usin (the c-speed one I linked):

Bore: 85mm
Stroke: 89mm
Combustion chamber: 39cc
Dome: 4.8cc
Headgasket: .029 (OEM)
Piston-to-deck height: .030

Which yielded about 12.8:1.

When I changed the headgasket thickness to .062 it gave me 11.64:1.

Hmm...

 

yes you are correct... my friend is the one who ordered and installed the gasket so I took his word for it. According to the link I should be at 11:6:1, except I have been in 11:8:1 setups that didn't ping even with stock timing, so either my timing is off or I have a thinner gasket? crap!

 

your set-up looks really nice non-vtec! Especially those valves

 

i got a killer deal on those......from a really cool HT.com member!