Checking piston to deck height
Checking piston to deck height Is rocking the piston and measuring the up and down movement per side, then adding the two numbers together and dividing them by two to get the average the proper way to measure piston to deck clearance? For example:
down = .015
up = .018
Total = .033
Average = .0165 deck clearance
down = .015
up = .018
Total = .033
Average = .0165 deck clearance
The highest amount above the deck is your number, if you average, the highest point will still hit first.
Bring the piston to TDC. Put a straight edge across the top of the piston and use feeler gauges to check the clearance between the straight edge and the block.
Make sure the block and the top of the piston are clean before you start.
Check more than one piston to see if the is any variance between them and use the highest number for you calculations.
You measure the deck parallel with the piston pin, front and rear edge, not top and bottom, they all rock in that direction.
.004 - .010 is the normal range.
Bring the piston to TDC. Put a straight edge across the top of the piston and use feeler gauges to check the clearance between the straight edge and the block.
Make sure the block and the top of the piston are clean before you start.
Check more than one piston to see if the is any variance between them and use the highest number for you calculations.
You measure the deck parallel with the piston pin, front and rear edge, not top and bottom, they all rock in that direction.
.004 - .010 is the normal range.
Thanks for helping me out. I just measured and they fall within the range you stated above with .010 being the highest. From you experience, which gasket thickness would you go with? A .041 thick gasket gives me .031 clearance. Will that be safe for FI (Force Induction).
The optimum quench is .035, don't go thinner than a .045 gasket if you are at .010.
What compression ratio (CR)are you shooting for? What are the rest of the specs? combustion chamber CC etc. With FI you need to watch the CR.
What compression ratio (CR)are you shooting for? What are the rest of the specs? combustion chamber CC etc. With FI you need to watch the CR.
Checking deck height parallel to the piston pin is .010 on two pistons. The rest are between .004 and .006. I'm shooting for 9.5CR although with my non quench blower pistons I may leave it in the 9.0 - 9.2 range. As for the rest of my combo, I have 72cc AFR heads and I'm running a LS1 iron 6.0 block bored to 4.006. The only gaskets I've found come with .041, .051, and .052 thickness. The .051 and .052 will put me in the lower 9.0 - 9.2 range. To clear this up you're saying that since those pistons come in at .010 I should set the clearance to those pistons.
Last edited by Monte4ever; Oct 12, 2009 at 12:13 PM.
