new pistons and cams confussed with compression HHHEEEEELLLLLLLPPPP!!!!!

**big tone** · 10-09-2012 07:36 PM

ok guys as it states.. and before anyone says anything yes i have searched and come up with nothing that was relivent.

i have a B18C7 which i am rebuilding. i do have an S300 for tuning.
I've purchaced a new Skunk2 pro I M, pro 70mm TB, Pro valves, Pro dual valve springs.
now this is where im lost. i want to run with either Skunk2 pro 1 or pro 2 cams, now to run these cams i have to have atleast 11.5 comp for the pro 1's and 12.1 comp for the pro 2's.
ive looked into what pistons to run and the CTR keeps popping up but i havent found a correct answer on what comp that will kive me.. some ppl say 11.6 and some say upto 12.2 and thats with out shaving the head.
then ive ben told if i run the ctr piston i have a good chance that i will get piston 2 valve slap. ( is this true or can i run them safely??)

If i stay with the P73-00 piston and shave the head so i get 11.5 cop am i going to run into dramas with valve/piston clerance aswell???

im not really interested in forged pistons either. i want to run the oem piston for reliability

**dougie_504** · 13-09-2012 01:48 PM

Best to get the piston/valve clearance checked by a machine shop.

Might be a good idea to clay the engine, put clay in the cylinder and see if the valves touch the clay etc. Might need to enlarge the valve reliefs on the piston tops.

Sorry I have no idea about the CR

**dougie_504** · 13-09-2012 01:50 PM

See if a website like this can help you out. You may need I enter some new values for the AUDM B18C7.

http://www.zealautowerks.com/bseries.html

**gen2 CRX** · 13-09-2012 09:23 PM

Get flat faced valves and 2layer head gasket. Ctr pistons will bring compression over 12 and no good for street

**dougie_504** · 14-09-2012 12:24 AM

Why not good for street? Ping?

A big cam and a good time should be fine.

**gen2 CRX** · 14-09-2012 02:27 PM

the motor is guaranteed to ping

**big tone** · 15-09-2012 08:23 AM

Originally Posted by gen2 CRX

the motor is guaranteed to ping

please explain how its going to ping?

ive already got the valves and the 3 layer gasket. its the pistons im really trying to work out. ive been told NOT to run ctr piston as i will have clearance issues. then i have been told that ctr pistons will be fine as long as i haven't shaved the head too much (which i have not even touched yet.)
the cams im going to run is the Skunk2 pro 1's or pro 2's
i dont want the CR to be waaaaaaaaaay over 12.1 hence why im only running upto pro 2 cams as an option. skunk2 has informed me that thay will run great starting at 11.9 cr but 12.2 would be better.

the car is a raod reg track car with the occasionall cruise. i want it to remain reliable as well so i dont want it on its edge 24/7 but i do want to get some power gains out of it.

**dougie_504** · 15-09-2012 09:21 AM

Valves regular size?

**gen2 CRX** · 15-09-2012 10:00 AM

Originally Posted by big tone

please explain how its going to ping?

ive already got the valves and the 3 layer gasket. its the pistons im really trying to work out. ive been told NOT to run ctr piston as i will have clearance issues. then i have been told that ctr pistons will be fine as long as i haven't shaved the head too much (which i have not even touched yet.)
the cams im going to run is the Skunk2 pro 1's or pro 2's
i dont want the CR to be waaaaaaaaaay over 12.1 hence why im only running upto pro 2 cams as an option. skunk2 has informed me that thay will run great starting at 11.9 cr but 12.2 would be better.

the car is a raod reg track car with the occasionall cruise. i want it to remain reliable as well so i dont want it on its edge 24/7 but i do want to get some power gains out of it.

OK, Whats your reason for not wanting compression way over 12? More compression = more power doesn't mater what cams you have.

**big tone** · 15-09-2012 04:55 PM

well ive had too many ppl say that running over 12.5 is not good for a track car running at long periods. drags ok but not track as it will prolong the engine..
i do know if im going to be running over 12.5 ill have to be considering other fuels higher than 98. as pinging will come into it with shit fuel. so if i can keep the comp down then i am keeping the engine to a more reliable..

Gen im not doubting what your saying but all i get is ppl say dont do this dont do that but with no evidence to back it up.. if i can run CTR pistons and not have any dramas with theengine then thats where ill head. but ive spoken to a few well known honda builders/tuners and thayve said not to, only 1 honda builder/tuner owner has said it should be fine.
if i run with the 3layer gasket and std comp valves and then CTR piston will i run into and problems? IE p2v clearence? thats all.. and roughly would you know where id be with CR?? cheers

dougie, i have skunk2 pro valves std not high comp.

**gen2 CRX** · 15-09-2012 07:23 PM

Originally Posted by big tone

well ive had too many ppl say that running over 12.5 is not good for a track car running at long periods. drags ok but not track as it will prolong the engine..
i do know if im going to be running over 12.5 ill have to be considering other fuels higher than 98. as pinging will come into it with shit fuel. so if i can keep the comp down then i am keeping the engine to a more reliable..

Gen im not doubting what your saying but all i get is ppl say dont do this dont do that but with no evidence to back it up.. if i can run CTR pistons and not have any dramas with theengine then thats where ill head. but ive spoken to a few well known honda builders/tuners and thayve said not to, only 1 honda builder/tuner owner has said it should be fine.
if i run with the 3layer gasket and std comp valves and then CTR piston will i run into and problems? IE p2v clearence? thats all.. and roughly would you know where id be with CR?? cheers

dougie, i have skunk2 pro valves std not high comp.

The reason high compression will kill the life of your engine is because of detonation (ping/engine knock). Your compression will be over 12:0 with CTR pistons and the motor will ping using 98 octane. If you are going to drive this car on the street, forget about the CTR pistons..Unless you are willing to run the car on E85 fuel which will allow you to run really high compression without detonation however you will need new injectors, fuel lines, ect and a ECU TUNE which you will need either way.

I advise keeping your standard ITR pistons if you don't need to re-bore the block or get a set of oversize JDM P30 B16A pistons which are slightly higher comp then the ITR (if you need new pistons). To bump up the compression a little use a combination of shaving the head, high comp valves and a 2 layer gasket. You choose. Use a B series compression calculator off the net to give you a rough idea of the compression you will make. I wouldn't go above 11:6 for daily driving.

**big tone** · 16-09-2012 09:20 AM

cheers for that..
the daily driving would be like once like every 2 months or so..
but in saying what you just said im going to try and get the comp around 11.6, i however allready purchaced the valves std comp.. but i will see what i can do to exchange them..
so would purchacing p73-00 @ 81.5mm help with CR? or not enough to notice.