Compression Ratio

[jtodd5781]

If I put a Gen 2 crank into a Gen 1 using Gen 1 rods and pistons, with the stock Gen 1 having a compression of 11:1, how much will the compression ratio increase with the increase of 2mm on the stroke?

 

[Dennis]

My rule of thumb is a mm spacer makes about 1 point of compression, so it would be around 12:1. Something to consider is that your pistons will probably be protruding from the block at the top of the stroke which is not good. You will probably have insufficient piston to valve clearance also. If you are doing a budget build you might be better off getting a set of Gen2 pistons and rods. Stock compression on Gen2 is 12.5:1 but I'm not sure if there is a difference with a Gen1 head.

 

[michael parris heuberger]

My rule of thumb is a mm spacer makes about 1 point of compression, so it would be around 12:1. Something to consider is that your pistons will probably be protruding from the block at the top of the stroke which is not good. You will probably have insufficient piston to valve clearance also. If you are doing a budget build you might be better off getting a set of Gen2 pistons and rods. Stock compression on Gen2 is 12.5:1 but I'm not sure if there is a difference with a Gen1 head.

Hi. That is what I am doing, but my custom made JE piston are 10 to 1s and I am using a spacer plate as I will be a turbo.

 

[Berlin Germany]

If I put a Gen 2 crank into a Gen 1 using Gen 1 rods and pistons, with the stock Gen 1 having a compression of 11:1, how much will the compression ratio increase with the increase of 2mm on the stroke?

if the crank change goes to worst the pistons crush the valves

do all the measuring in 1/100 of a millimeter