Thread: 500 hp/550 lb-ft from a 390?

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Just wondering one thing. Speed Pro piston is designed for connecting rods that are 6.480.
Are they not 6.490? Maybe it doesnt matter?

Johan

Originally Posted by Johan78

Just wondering one thing. Speed Pro piston is designed for connecting rods that are 6.480.
Are they not 6.490? Maybe it doesnt matter?

Johan

When you are sitting down to engineer all the parts that will make your motor work like you want it to, you determine the static compression ratio and squish you want to use in the motor, then purchase parts to reach those specifications.

Let's say for instance, that you wanted to achieve a squish of 0.040". OK, we know the block deck height is ~10.170", so we have to put together a stack of parts and adjust the block deck height to achieve a zero deck to do this. The thickness of the gasket then becomes the squish figure. So, with a stack of parts like this.....stroke radius 1.890", rod length nominally 6.490" (can vary from 6.486" to 6.490" in production rods) and piston compression height of 1.776", we would add all the stack pieces together and find that we have a stack of 10.156" So, in order to achieve a zero deck, we would have to shave the block decks 0.014". If the rods were actually 6.480", then the stack would be 10.146" and you'd have to cut the block decks 0.024" to achieve a zero deck.