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Old 12-21-2009, 01:46 AM
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If you have the stock L-31 short block sitting in front of you and it really matters to you, why don't you measure the piston's actual dish volume and piston deck clearance @ TDC OF YOUR MOTOR and then calculate the real compression ratio and tell us.

To measure the combined volume of the piston dish, valve reliefs and piston deck clearance @ TDC on your assembled L-31 short block, you will need a old CD rom disc, some common household Vaseline Petroleum jelly and a graduated cylinder (100ML) (your local drug store pharmacist counter)

The vaseline is used to seal off the gap between the piston's edge in the cylinder (@TDC) and cylinder wall and to seal the CD ROM disc to the deck of the block.
Just spread the vaseline around the pistontop/cylinder edge with your finger to make a temp water proof seal.
You need a accurate method of getting the piston to exact TDC. (piston stop or dial indicator w/stand)

You pour the water (100ML) from the 100ML graduated cylinder thru the hole in the CD ROM disc (mounted on the deck of the block) until the cylinder is full of water. The volume in CC's is the amount now missing from the cylinder. ( Subtract the water remaining in the graduated cylinder from 100.
1ML = 1 CC

Not that hard.

Now you have accurate numbers to calculate the real compression ratio with X cylinder head and Y head gasket volume.

When you are done just wipe the vaseline off the piston and deck.

Weather the Edelbrock Performer RPM Camshaft included in the Edelbrock Top End Kit is the right cam or best cam choice for your vehicle and intended purpose is another thing.
some tools you'll need

Last edited by F-BIRD'88; 12-21-2009 at 02:00 AM.
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