Piston Selection

[alldodge]

But, if I went w/ the flat tops w/ the 4 VR I felt my compression would be too high

Not commenting to change your mind, just a comment, Your compression is based on every change. Zero decking the block, thin head gasket, flat top or dish pistons all change compression. If block is zero decked and thin gasket is to high compression so dish piston is the way to go to reduce compression. Your basing quench on the top edge of the piston, the rest of the piston is in a hole

 

[FreeBeeTony]

Not commenting to change your mind, just a comment, Your compression is based on every change. Zero decking the block, thin head gasket, flat top or dish pistons all change compression. If block is zero decked and thin gasket is to high compression so dish piston is the way to go to reduce compression. Your basing quench on the top edge of the piston, the rest of the piston is in a hole

​Compression was not based on a zero deck......0.015 actually, 0.025 gasket, piston 0.012 in the hole w/ a 7cc piston volume.
This would have given ~10:1.....didn't want to get that high.

​With my choice in piston I should have ~9.6:1..........and a better quench.

I now feell like I am getting what I wanted from everything I have learned.

​I am an engineer by trade and delve into numbers,,,,,,,,,I told the machinist this.
​He told me I was experiencing "paralysis by analysis".........can't really disagree but I wanted what I thought was best.

 

[alldodge]

An OSO posting had something come to mind that I didn't think of at the time. Using a dish piston just raises the deck. If a .040 gasket was used the a flat top piston would be about the same as a thinner gasket and a dish piston. Your trading one for another. While 40 quench is the point to shoot for. a 44 quench is not a problem.

 

[FreeBeeTony]

An OSO posting had something come to mind that I didn't think of at the time. Using a dish piston just raises the deck. If a .040 gasket was used the a flat top piston would be about the same as a thinner gasket and a dish piston. Your trading one for another. While 40 quench is the point to shoot for. a 44 quench is not a problem.

​So are you saying my reasoning is correct???

 

[alldodge]

​So are you saying my reasoning is correct???

No, I would still like to see flat top, but that's just me. If you used a .040 gasket and flat top you get about the same as a dish and thinner gasket, your trading one for another

 

[scoflaw]

No, I would still like to see flat top, but that's just me. If you used a .040 gasket and flat top you get about the same as a dish and thinner gasket, your trading one for another

​Flat top piston at 0 deck would put him way over the top in CR running a marine cam. A dished piston still has a flat top around the perimeter, so using a thinner gasket won't work.

 

[FreeBeeTony]

Should be receiving my pistons today and gonna bring them down to the machinist.
Anyone have experience w/ piston-wall clearance?
These KB pistons are calling for a 0.0030-0.0045 clearance.

 

[Bondo]

These KB pistons are calling for a 0.0030-0.0045 clearance.

Ayuh,.... Then that's the clearance ya want,.....

 

[FreeBeeTony]

Got the pistons tonight........only received 6!!
​returning for a set of 8!!!