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im bout to put a high compression zc pistons into my z6 how good would it run and wut would xactly be the compression ive heard different things
 

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compression alone will only do so much. think of the whole system.
if everything else is stock just the pistons, your much better off putting the money into the head. would be a lot more streetable and fun.

m
 

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Hey Supastyl, are you using A6 pistons on your Y8? What's your compression right now? Were your running on 91 octane gas that you had to retard the dizzy that much? We have 96 octane here and I'll be reaching around 11.2:1 c.r. on my build so would you say I'd still end up pulling timing?
 

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Hey Supastyl, are you using A6 pistons on your Y8? What's your compression right now? Were your running on 91 octane gas that you had to retard the dizzy that much? We have 96 octane here and I'll be reaching around 11.2:1 c.r. on my build so would you say I'd still end up pulling timing?

you better check the cr chart again! :lol:
z6 block and head with pm7 pistons even with a thick a6 head gskt = 13.1:1 cr! ;) but yeah, have it tuned for the fuel that you want to run in it!
my a6 with pm7's has 12.2:1 and i have to have the timing set back to run it on 93.
 

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^your calculations are wrong for both your setup and the z6 set up unless your head is REALLY milled.

the z6 head/block with z6 headgasket is right at 12:1


m.
 

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^your calculations are wrong for both your setup and the z6 set up unless your head is REALLY milled.

the z6 head/block with z6 headgasket is right at 12:1


m.
ok i did it on 4 diff. cr calculator sites.
d series 1.6 bore & stroke = 75 x 90 mm
Z6 head cc = 34.6 cc's
Z6 block deck height = .000
Z6 head gskt thickness = .037 in.
PM7 piston dome cc = 7.2 cc's

come's out to 13.6:1 cr

same as above with thicker A6 head gskt that's .048 come's out
to 13.1:1

and my A6
same bore n stroke 75 x 90
head cc's = 38 cc's
block deck height (decked barely .004 to check for trueness) = .016 in
Y8 head gskt thicknes = .025
PM7 pistons again = 7.2 cc's

come's out to 12.2:1 cr :D
 

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Yea, PM7/P29 sit 1mm/.040" down on Z6/A6 bore.

dont take this the wrong way, but this is where you guys are getting it wrong. lol
with PM7 pistons, the deck height in
a D16a1 is .040
a D16a6 is .020
and a D16z6 is .000
the blocks are decked different.

on my d16a1's, i always deck them .040 for pm7's
and .020 on my d16a6's other than the one i'm running right now. it's was barely cut at .004 just to make sure it was flat, and i measured the deck on it, and it was .016
now if you use the almost flat top 86/87 d16a1 pistons in a z6 block, they will actually come out of the bore a lil bit because the tops sit higher than the pm7 pistons. that's why they only went from 9.3:1 cr in a 86/87 d16a1 to 9.5:1 cr in a 88/89 d16a1, even though the pm7 has a dome on it. :)
but yeah, i always have my engine builds machined and i always double check everything to be sure it's right. :D
 

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i posted the above photo for you to figure it out. Its pm7's at the top of the stroke in a z6 on a z6 rod.
they sit .040 in the hole in a z6. If i have to i will dig through my notes and give you all the numbers. you do have it wrong though. I am not the only one with this combination and this conclusion.


m.
 

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A6 and Z6 blocks are the same 212mm deck height.

overall deck = 212mm
rod length...= 137mm
1/2 stroke....= 45mm
pm7 comp ht = 29mm



subtract those numbers from 212mm and your left with 1mm, that is how much the piston will sit in the hole on a undecked factory spec block.

In stock form........

A1 with 29.00 comp height are .040 in the hole
A6 with 29.50 comp height are .020 in the hole
Z6 with 30.00 comp height are zero with the deck.

It's the pistons that are changing, not the blocks.
 
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