Piston gap

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mbrooks573

mbrooks573

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Hi, my dad and I are rebuilding a /6 for a 64 Valiant convertible. It's back from the machine shop, .030 bore, and we are putting it back together. Only problem is a gap between the top of the piston and the block deck - probably about 1/16th of an inch. Any ideas? Did the machine shop get the wrong length pistons? Just curious if anyone has encountered this before. Thanks for the help guys
 
That's not where piston to wall clearance is measured. It is measured between the piston skirt and the cylinder wall.
 
The gap at the top of the piston is usually wider to accomodate for piston expansion due to heat. Usually you take a measurement on the skirt just below the oil ring (for piston to wall clearance).
 
Sorry, I mean the top of the piston to the top of the block has a small gap (top of piston and block are not flush). Piston diameter looks fine.
 
I used to build engines and we never worried about the deck to piston height if it was a stock motor. (as long as your using stock replacement parts.) You need some in there anyway so the piston can grow when hot so it don't crash into the head. Some people will 0 deck a block to the pistons and play with head gaskets thickness to get the quench area where they want it for compression ratio.
I'm sure there's a spec in the service manual for rebuilding that year of engine. Then use a depth mic to measure the distance and check with acceptable tolerances. This is the proper way to do it. Most people just toss it together and it works just fine.
Paul
 
mbrooks573 said:
Sorry, I mean the top of the piston to the top of the block has a small gap (top of piston and block are not flush). Piston diameter looks fine.
Click to expand...

Slant six. They all sit in the hole around .100" give or take. Normal.
 
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