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Piston Height

Posted: Mon May 12, 2025 5:26 pm
by Craig Leach
Hi Everyone,
I'm looking to install a RICARDO PAT NOV 13 1923 HEAD & would like to send it out to have it surfaced .010 to get a better gasket seal but I'm
concerned about piston clearance. The current area over the piston is .423 so I would end up with .413 with a gasket crush of .050 to .060.
I have found info on line of the stock compression pistons being from .378 to .412 proud of the block. The pistons I have use the 5/64" rings
& I have been told they are Jann's. As far as I know the block has not been decked. Doe's anyone have a engine apart that could measure how
proud their pistons are? Thanks Guy's.
IMG_2997.jpg
IMG_3007.jpg
Those are not cracks!
Craig.

Re: Piston Height

Posted: Mon May 12, 2025 5:39 pm
by Kevin Pharis
You will find that the only consistency in model T production… is the inconsistency! I agree that the 3/8” piston height is the target, but rod lengths are determined by a tape measure on many babbitt boring setups. Have seen tapered blocks, long/short rods, etc… You should measure what you’ve got

Re: Piston Height

Posted: Mon May 12, 2025 7:59 pm
by Allan
You could put the head on with no gasket and turn it over. No interference = no problem. There is no need to surface the head to .010" if it cleans up at .005" After this, you may have variables to deal with.

Allan from down under.

Re: Piston Height

Posted: Mon May 12, 2025 8:04 pm
by Dan Hatch
In picture of bottom of head. The top cly is that a crack?
I always pressure test any head I send to be decked.Dan

Re: Piston Height

Posted: Tue May 13, 2025 12:44 am
by Craig Leach
Hi Dan, no it is not a crack it washed off with brake clean. I did Magnaflux the head but not able to pressure test. The pits around the water ports are more than .005

Re: Piston Height

Posted: Tue May 13, 2025 9:05 am
by bobt
Put a ball of modeling clay on top of each piston then put the head on and crank it over and remove the head and see how much you squish the clay. You can buy the clay at the dollar ($1.35) store. bobt