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Discussion Starter · #7 ·
wouldnt it be too much compression or would it work ok, it calculated 13.6:1 ratio of compression. What would I need in order for it to work properly with the 88-89 zc pistons? using the fact that I have a skunk2 camshaft with kms valve springs and retainers.
 

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jlicrx said:
86-87 D16A1 pistons have basically a flat top - 88-89 D16A1 pistons have a dome - quite a bit different
Yep the 86-87 are p29's and the 88-89 are PM7's. There were some PM7's found in the earlier blocks tho, i dont know why but ive seen pm7s in a 87 d16a1 before. I also believe the 88-89 had a D16A3 block.

And, before you put those PM3 Pistons in that 1.6L block do some measuring.

1.6L deck height = 212mm
1.6L rod length = 137mm
1.6L stroke = 90mm
P28(d16z6) Piston compression height = 30mm

Now take these numbers and do some crunching to find the piston to deck clearance: Deck height - rod length - compression height - Stroke/2

212-137-30-(90/2)=0mm
So the P28 piston is even with the edge of the deck, now do that with the PM3

212-137-30.7-(90/2)= -0.7mm :The Negative value means out of the hole, I.E. sticking out of the block. Now this piston might still work(depends on head and headgasket used), but you need to clay the motor for clearances if you want that piston.

Now the PM7 goes like this:

212-137-29-(90/2)=1mm or about .040" under the deck height, which means it will produce only 12.0:1 compression ratio in the Z6 with Z6 headgasket and stock unmilled head instead of 13.6:1, thats a big difference.
 
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Discussion Starter · #9 ·
claying

sonictronic said:
Yep the 86-87 are p29's and the 88-89 are PM7's. There were some PM7's found in the earlier blocks tho, i dont know why but ive seen pm7s in a 87 d16a1 before. I also believe the 88-89 had a D16A3 block.

And, before you put those PM3 Pistons in that 1.6L block do some measuring.

1.6L deck height = 212mm
1.6L rod length = 137mm
1.6L stroke = 90mm
P28(d16z6) Piston compression height = 30mm

Now take these numbers and do some crunching to find the piston to deck clearance: Deck height - rod length - compression height - Stroke/2

212-137-30-(90/2)=0mm
So the P28 piston is even with the edge of the deck, now do that with the PM3

212-137-30.7-(90/2)= -0.7mm :The Negative value means out of the hole, I.E. sticking out of the block. Now this piston might still work(depends on head and headgasket used), but you need to clay the motor for clearances if you want that piston.

Now the PM7 goes like this:

212-137-29-(90/2)=1mm or about .040" under the deck height, which means it will produce only 12.0:1 compression ratio in the Z6 with Z6 headgasket and stock unmilled head instead of 13.6:1, thats a big difference.
What do you mean by claying the motor for clearances? also, my head is milled .40 and one layer gasket :( and pm6 pistons, what compression ratio would it be on this combination? by the way can it still work with the pm3 pistons? and what compression ratio would it be on these? thank you for clearing many of my doubts :) I really aprecciate it, hope you answer soon
 

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Hmm, you said the head is milled .40....is that in mm or inches, if mm then its not much but inches, thats a lot. Since the head is milled id say the PM3 pistons wont work, we had tight clearances on our 1.6L block with a non vtec head, the vtec head quench area is even closer to the block than the non vtec, so id say nope on the pm3s.

edit, and since youre head has been modified, you will need to have it CC'd again to find the combustion chamber volume and the thickness of the headgasket compreesed to get a new compression ratio value.
 

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Discussion Starter · #11 ·
sonictronic said:
Hmm, you said the head is milled .40....is that in mm or inches, if mm then its not much but inches, thats a lot. Since the head is milled id say the PM3 pistons wont work, we had tight clearances on our 1.6L block with a non vtec head, the vtec head quench area is even closer to the block than the non vtec, so id say nope on the pm3s.

edit, and since youre head has been modified, you will need to have it CC'd again to find the combustion chamber volume and the thickness of the headgasket compreesed to get a new compression ratio value.
its .40mm, what about claying? I really need more compression on my motor, what would be the ratio with my pm6? remember I have an agressive camshaft, higher compression would make more power, what should I do??
 

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I cant give a compression number without knowing the new CC volume of the combustion chamber. I can give you compression numbers for stock heads and thats all, unless i have the specs for the modded head.

I can however do some educated guessing:

.4mm is 20 thousandths of an inch, so i can run the number through the compression calculator as if it didnt have a head gasket and get a roundabout number...10.8:1 is the number i get with no headgasket, so in order to get that number by playing with the head cc's i get the head has 32cc combustion chambers now, so lets feed this into the calc....

z6 head and block, 32cc combustion chambers, pm6 piston (3.4cc dish), 1layer head gasket (.015 thick im guessing at the thickness here, a 2 layer is .025 and a 3 layer is .037) and you get 11.1:1

The A1 pistons (7.2cc dome) come up to 13.8:1, so they are pretty much out of the question.

As far as claying goes, there is a good writeup on it here http://www.knology.net/~jediklc/pistonnotes.htm

Claying the motor means you have to have it completely assembled and turn it over with the clay on the tops of the pistons. Then using a special tool you can measure the thicknes of the clay to see how much clearance you have, but of course if the motor stops or hesitates at any time, you are way to close and cant use that setup. That happened with me on one motor before. I tried using the 86-87 a1 pistons in a motor and the valve reliefs were not deep enough and caused clearance problems.
 

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Discussion Starter · #13 ·
sonictronic said:
I cant give a compression number without knowing the new CC volume of the combustion chamber. I can give you compression numbers for stock heads and thats all, unless i have the specs for the modded head.

I can however do some educated guessing:

.4mm is 20 thousandths of an inch, so i can run the number through the compression calculator as if it didnt have a head gasket and get a roundabout number...10.8:1 is the number i get with no headgasket, so in order to get that number by playing with the head cc's i get the head has 32cc combustion chambers now, so lets feed this into the calc....

z6 head and block, 32cc combustion chambers, pm6 piston (3.4cc dish), 1layer head gasket (.015 thick im guessing at the thickness here, a 2 layer is .025 and a 3 layer is .037) and you get 11.1:1

The A1 pistons (7.2cc dome) come up to 13.8:1, so they are pretty much out of the question.

As far as claying goes, there is a good writeup on it here http://www.knology.net/~jediklc/pistonnotes.htm

Claying the motor means you have to have it completely assembled and turn it over with the clay on the tops of the pistons. Then using a special tool you can measure the thicknes of the clay to see how much clearance you have, but of course if the motor stops or hesitates at any time, you are way to close and cant use that setup. That happened with me on one motor before. I tried using the 86-87 a1 pistons in a motor and the valve reliefs were not deep enough and caused clearance problems.
so would you recommend the a1 or the pm6 that I have?, thanks for your time.
 
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