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Discussion Starter · #1 ·
Head + Pistons = Compression
Z6 Z6------------9.2
Z6 Y8------------9.27
Z6 A6------------9.7
Z6 ZC------------11.58
Z6 86-87 A1------11.27
Z6 88-89 A1------11.58

This is something I have found and have been going by. However, the link on this site (somewhere) says that the zc pistons will give you like a 14:l compression ration???

Is something off here or am I just missing something???????

Discussion Starter · #3 ·
I have these numbers plus I have seen two other 'calculators' and they all give deifferent numbers with a WIDE range.

There was some discussion going on in a thread in the classifieds section but that was not the place for it.

I would really like to get some solid information on this. Some figures I have found differ by 3:1 compression which is CRAZY!!!!!!!!

Discussion Starter · #5 ·
P29 pistons in an otherwise stock D16Z6 engine even with the stock Z6 metal headgasket doesn't net 14:1 CR, it only nets 12.0 CR.

Trust me.

Here's the compression calculator:

And here's the numbers you punch in:

Bore - 75
Stroke - 90mm
Combustion chamber volume - 34.6
Piston dome - +7.2
Head gasket thickness - .037
Piston-to-deck height - .040 <------------------- thats what throws everything off.

CR comes to 12.03 with a displacement of 1590cc

I bolded the piston-to-deck clearance because too many people use the wrong number here. You need to use the number for the *PISTON* going into the block, not the block itself.

Had I punched in the piston-to-deck number for the D16Z6 I would have gotten a way incorrect 13.6:1.

There have been many pump gas D16Z6 engines built with P29 slugs, so that alone should tell you that the 14:1 number is wrong.

The only thing to watch out for with the P29 pistons with a VTEC head are the valve reliefs. they do not latch up the same, but they do clear unless you go crazy with the mill or have some crazy-ass cam with a shitload more lift than stock.

I'd go with the least amount of mill on the head and not deck the block to ensure good piston-valve clearance.

If you need the D numbers here they are:

12:1 is 100% totally streetable on 93 octane fuel. Hell I've got a few friends running 12.5:1 on pump gas too. These are B VTEC builds making over 200whp on pump gas that ar also daily driven with zero problems.

So my point is that I think you should run at least the flat top 86-87 pistons or even better, the P29s fropm the 88-89 Integra.

I fell victim to the misleading info before someone correceted me. A very knowledgable person on honda-tech.

zc pistions (p29, pm7) would bump the compresison in a z6 almost to 14:1 depending on the headgasket. If you use the 2 layer y8 headgasket its 14.1:1. I am building an all motor z6 with a6 pistons and it runs close to 11:1 at 10.7:1 compression which is pretty deceont for a street car. Im aware that you arent supposed to run anything over 11:1 on pump gas, so i would try to get as close to tthat mark as possible here is a link

dx pistons arent a bad choice either...

two calculators with different results. PLus these differ with the data I have as well.



is not correct.

Discussion Starter · #7 ·
Cool. Thanks.

Can you varify or dismiss the following info also AND give you give me some facts as to why like in the above? That way I can go to where I got my info and try to correct them also.


Never mind the site is down. I will have to post it up later.
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