D16y7 - What pistons for 10.5 C/R

[underage]

I've looked at P29s and Pm3s but I'm concerned about valve clearance. I will probably run a Delta 272 cam. Also the pm3s show a negative piston to deck height, which means they stick out of the top of the cylinder, correct?

So I guess my question is... Will P29s or Pm3s work in a D16y7 with a Delta 272?

Thanks

[Red_SiR]

I've looked at P29s and Pm3s but I'm concerned about valve clearance. I will probably run a Delta 272 cam. Also the pm3s show a negative piston to deck height, which means they stick out of the top of the cylinder, correct?

So I guess my question is... Will P29s or Pm3s work in a D16y7 with a Delta 272?

Thanks

I've heard it works without clearance issues but go the safe way and clay it first...

[underage]

I guess I'll have to. I was just wondering if anybody had experience with either piston because then I could just buy a known to work solution instead of grinding a larger relief in the piston or something like that.

[cvic90]

PM6 pistons will get you around 10.8:1. And P2P pistons will get you 10.2:1. Then you could get flat valves to get into the 10.4 range

[underage]

I don't think you did your math correctly. They both have less compression height than the D16Y7 piston (.5 mm less) and their dome height/displacement isn't enough to offset that. According to the zealautowerks calculator, Pm6 pistons will get me around 10:1 with a 2-layer d16y8 headgasket.

[Honda4VW]

P29's and stage 2/3 crowers with thickened headgaskets are a common find in the high compression n/a world. Valve Clearance is not an issue

[underage]

ok, thanks. I think I'll just end up claying it first.

[Eyal 951]

I don't think you did your math correctly. They both have less compression height than the D16Y7 piston (.5 mm less) and their dome height/displacement isn't enough to offset that. According to the zealautowerks calculator, Pm6 pistons will get me around 10:1 with a 2-layer d16y8 headgasket.
I'm running PM6's (.040 over) at about 11.4:1 CR with a smidge over 30 thousands total removed from block, head and 2 layer hg. Their good pistons since they are a flat dish.
P29's are common as well, but if your only looking for 10.5, according to this compression calc: http://www.knology.net/~jediklc/dcalc.htm and zero piston to deck height, and 3 layer hg, you're looking at 14.3:1 CR. Unless there is something different about the y7 I don't know.

the PM6, and 2 layer hg, .020 piston to deck height gives to 10.63:1 CR.

Why don't you want to go for 11:1 CR?

[sie7e]

I heard of use the PM3 psitons is teh best way for the d16y7. I have one of this. I will try this setup in the future.

[underage]

well, I guess I should clarify. I was looking for at least 10.5:1, but no more than 11.2:1. I didn't even think about trying to combine PM6's with milling the head to get more compression, but that probably would be the best way. I also have a D16a6 I want to rebuild for boost, so that would leave the pistons available, but I don't know how wise it would be to use 200,000 mile pistons in a build.

Also, I don't need zero piston to deck height, I just didn't know it the pm3's would be good because they are out of the hole (according to the calc I used).

[underage]

well, I found the difference. One calculator (knology) says that the Y7 combustion chamber volume is equal to the Y8 at 32.8 cc. The other (zealautowerkz) says that the volume for the Y7 is different at 38 cc. Other than that I get equal numbers. I guess the next step is to search to see which is true.

[DirtyDC4]

Zeal's used to say the Y7 head had the same cc as the Y8. They changed it a few months ago.

[devere]

well, I found the difference. One calculator (knology) says that the Y7 combustion chamber volume is equal to the Y8 at 32.8 cc. The other (zealautowerkz) says that the volume for the Y7 is different at 38 cc. Other than that I get equal numbers. I guess the next step is to search to see which is true.

Neither of these is correct. The size of the Y7 combustion chamber is 34.6cc, the same as the Z6.

I did make a point of posting these were incorrect a while ago, but i dont think anyone really looked at it.
http://www.d-series.org/forums/showthread.php?t=40551

[underage]

Yeah, I came across the 34.6cc when I searched, but there was conflicting "facts" so I wasn't sure. Thanks for clearing that up.

I decide to use the pm6 pistons in combination with milling the head like suggested above. Thanks for the help.