Just curious I see them advertised as will increase comp by "x amount" but skunk/other flat valves are 450+ and the thinner HG's usually 200+ so all in 600+. My question is it worth it to look into such items ? I'm not considering these items just curious or would you guys consider them along the lines of engine bay dress up washers lol useless and provide no real benefit. Did search but didn't find the answer I was looking for.

TIA

 

Comtetics HG's are about 130 max..

Did you plan your engine build and get the CR yet?

Personally, I wouldnt do valves unless they needed to be replaced, but milling and HG to accentuate your piston selection/CR would be where I would look to.

Just my .02

 

like mentioned above, the valves are definitely not worth it unless you need new valves as it is. they really only bump compression about 1 or 2 tenths.

thinner HG will make a decent difference though, so long as you aren't running big cams that could stuff the valves into the pistons.

 

Stock ITR intake valves, Flat Exhaust valves and any proven 2 layer headgasket would be what you should be shooting for, IF yours are damaged anyway. If your already that close to the piston that a 2layer HG will mean contact you are doing something wrong.

 

CR goal, yes I have Skunk2 tuner 2's waiting to go and get tuned in once I figure out how to achieve a bit above 11:1-ish comp. Engine is a healthy b18c1 any suggestions on how I could up the C/R to that without touching the block ? I don't trust my self to do that yet lol that's why I know different pistons would do it but ya....

 

Bump any suggestions on how I can achieve this without touching the block ?

 

well, your supposed to change CR with pistons which is the correct way.

You can mill the head and just use a OEM headgasket.

find your specs here:
http://www.zealautowerks.com/bseries.html

The HG part is a little off. The OEM 3 layer shows .026 but mine was .023 after crush

 

The head has had a bit taken off before(slight offset to the timing marks on the side of the cam gears) i'm using a gates racing belt if that matters to that. Is it possible to mill the amount off to reach the comp I'm looking for ? I know messing with the rotating assembly is the correct way I'm just not skilled enough to try that.

(10:0:1 to 11:1ish)

 

when you mill the head, you change the piston to valve clearance.

you would need to clay it to see how much you can mill. If you mill too much, you can compensate with a thicker HG from Cometic


theres the service limit indicators (circle) which I believe is .020 from the oem thickness. but dont quote me on that.

 

I highly doubt you'll achieve 11:1 just by shaving, even if you shaved both the block and the head to their max service limit. and as said above, it'll bring the valves closer to the pistons, potentially causing contact, especially with big cams

 

Was expecting to hear that... damn. so would PR3 pistons give me the C/R i'm looking for ? I may just hold off and learn so more over the winter.

 

you need to do your own calculations

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

 

According to the calculator they should do the trick. quick question(s) I plan on honing the CYL's(obviously) if I do so will I still be able to use 81mm pistons ? I was thinking of going with RS Machine ones and getting the wrist pins pushed from my old gsr rods. thx

 

that all depends on how much wear your cyls have. it'd need to have very minimal or zero wear to be able to use stock bore pistons on freshly honed cyls and not exceed the recommended clearance. this is the exact reason for oversizes. best bet is to go 81.5mm, or larger. then your cyls will be totally fresh and you'll know you can achieve perfect clearances. and remember, larger bore = higher displacement, and there's no replacement for displacement.

 

11:1 is a nice cr to shoot for on a street motor. USDM ITR pistons should net you right around ~11.1:1 with a gsr head.

Don't get hung up on the super high compression thing if you're only doing a street motor. Modern gasoline sucks and is only getting worse, and you're most likely running a primitive ecu with no real knock protection. You can make power at reasonable cr's.

If you do decide to do pistons, don't commit yourself to a bore size until the motor is apart and measured. I prefer to do a hone before I decide if I'm going to bore or not. Once you decide how much work the cylinders need you can order pistons.

 

Remember that cam choice effects compression. Theres static and dynamic compression ratios and you can get away with higher compression by using larger cams on pump gas. I'm almost certain I will be going with a 2 layer head gasket when I upgrade my cams just to keep the cylinder pressures up. With JDM ITR pistons it should be around 11.3-11.4:1