viciousknid

iTrader: (8)

One discrepency I noticed in your calculations is the deck height. I'll have to check it myself when I get all of this mustang stuff done but online I only find 9.800 deck heigh on a 454 apposed to the. 9.780 u mentioned.
If correct wouldn't that make the pin height 1.782"?

1Bear

iTrader: (1)

It’s not really a discrepancy, your right in that the stock deck height is advertised as being 9.800” and a tall deck block would have been 10.200”, but what I’m asking you do is look into is decking the block .020” to get the compression where you want it with out of the box type pistons. It probably needs close to that to square the block back up anyway and to zero deck it to the final piston height. This is where the machine shop comes in. What your going to run into (as you’ve already figured out) is finding few box stock parts that fit the dimensions your looking for and will need to make concessions. Another issue with just picking stock type components on a traditional big or small-block and hitting a given target compression ratio is, unlike today where it is common for the piston to protrude past the deck height, the pistons were typically located somewhere around .020” down in the hole.

If you didn’t deck the block and were trying to attempt a 0 deck height, yes indeed you would be looking for a piston with around a theoretical 1.785” pin height.

viciousknid

iTrader: (8)

I see. Thanks again. Just wanted to make sure I understood what needed to happen. I get what you mean. I'll let him know.

1Bear

iTrader: (1)

Another reason you’re finding conflicting information everywhere you turn, is GM played with the piston pin height for the various engine combinations.

For example:
Low Performance*********Pin Ht.
396-402-427*************1.770”
454********************1.640”

High Performance*********Pin Ht.
396-427*****************1.760”
(1968 Only)

396-402-427**************1.765”
454-502*****************1.645”

STXTahoe

1Bear, I have been building big blocks for years and I have yet to hear someone explain it correctly. awesome brother, just awesome.!!!