Originally Posted by denny1977
whats the deck heigt on a sbc.and whats the compression height on a 350 piston
How long is a piece of string? In terms of deck height, Chevrolet's casting and machining process often leaves a lot to be desired. Deck heights may vary 3 or 4 times on the same block. There is no way of guessing or going with factory specs, it must be measured and corrected. The factory specs were all over the place and there is no way to determine what has been done to a block that you haven't owned since manufacture.
Piston comp height is a term for denoting where the pin C/L is in relation to the piston top or, quench area on a wedge piston. I think less is better until you start cramming and squeezin your ring package together.
To check deck height you can use a steel mandrel inside the main saddles and torqued main caps (no inserts) and measure from the deck to the mandrel record the measurement and divide the mandrel diameter by 2 and add that to the overall measurment. You could do that on all 8 bores if you want....I dont recall off hand the mandrel dia for a small block so you'll have to check that. Make your mandrell 27 inches long and .0005 smaller then the minimum size saddle bores. Save this mandrel forever, it is also telling you something about align boring if it wont turn. It should turn freely or at least turn. The machine operator will/should be referencing off of crank centerline while decking and boring so its nice to know the saddles are all in a plane to begin with. Another way is to simply use a large throat mic and measure from the main saddle to the deck on all 4 corners. I like the mandrel though because it is alerting you to the possibility of align boring and that can be avoided by using another straighter block. After all this crap and still having a OEM thin deck block with bores that noodle, you can easily begin to see why an aftermarket block looks cheaper and better all the time IF YOUR LOOKING FOR HIGH/MAX PERFORMANCE. If, on the other hand you insist on max performance with a low performance block, your safety and the safety of others will be enhanced a little bit by having the block magnafluxed everytime its torn down.
At any rate, whatever the deck height ends up at RECORD THAT VALUE in case you scatter cast iron and need to reproduce that block to fit whats left of your rotating assembly combination.
Machine Shop Tom and K Star are probably pretty good sources to confirm or deny my process as being viable as I haven't had to mess with OEM stuff for decades now and for all I know the machine operators could be using GPS and Radar to Square Deck a block nowadays.