Thread: Piston position on 383

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Got the Eagle rotating assembly all ready to put together. It's
been a while since I put one of these together, so hope this question
doesn't sound to dumb. I put the rings on the pistons, and I know
about the rods but there is no arrow on the pistons for up or down.
The pistons are notched for valve clearance and I am just assuming
that when putting them on the rods the notches go in the down
position and the small dome goes upward. Correct me if I'm wrong.
Thanks

Bass Ackwards.

Stand beside the motor and look at the location of the spark plugs, referenced as top to bottom of the heads. They are on the bottom of the heads. You know that the spark plugs screw into the combustion chambers, so you know therefore that the chambers are on the bottom side of the head as you stand at the side of the motor and look at it. Therefore you know that the dish or dome that has to match up with the chamber must be on the bottom of the block as you view the short block from the side.
http://www.kimbarrracingengines.com/...74398394349fba

Before you begin bolting the motor together, tell me about the piston compression height in the block and how you engineered the squish and what the squish measurement will be. This is perhaps the most overlooked aspect of amateur engine building. Do you know the block deck height? Do you know the stack measurement? Did you cut the block decks to fit the stack? Don't be embarrassed if you don't know, it's OK. But let's get it worked out before you make a very costly series of mistakes.

I haven't seen any updates since your last thread, so I have no idea what the final plan was.

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Tech I don't know much if anything about squish. The pistons are
11 to 1 Comp. I was wrong about the domes. Don't really appear to have
any, but two nice notches for the valves. I could not tell much about
the picture you posted, but thanks.

Originally Posted by rdobbs

Tech I don't know much if anything about squish. The pistons are
11 to 1 Comp. I was wrong about the domes. Don't really appear to have
any, but two nice notches for the valves. I could not tell much about
the picture you posted, but thanks.

To say that you have 11.0:1 pistons means that all the accompanying values (cylinder volume, combustion chamber volume, piston deck volume, head gasket volume) have to be exactly what the piston manufacturer used to determine that he was building 11.0:1 pistons. Pistons by themselves do not determine the static compression ratio. It is determined by the 5 values added together and then divided by the sum of the piston deck volume, head gasket volume and chamber volume.

Stock Chevy heads have the valves angled at 23 degrees from the centerline of the cylinder bore. Can you stand at the back or front of the short block and visualize that the valve pockets in the piston crowns are angled a little toward the top of the motor?

Bottom line: Are you willing to loosen up and share some valid information so that we can help you, or are you going to wing it alone, asking single questions one after the other? It's no skin off my nose either way.

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Tech, valve pockets are angled toward top of motor. Have selected heads
or cam yet.

Sorry, duplicate post.