piston help
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Elder User
Joined: Jan 2004
Posts: 867
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From: Eastern Pa
piston help
The pistons out of my 390 have no numbers on that I can find, just "std" on the top. They are dished and the dish is exactly 2.5" diameter and of course the valve pockets. The distance from the center of the pin to the top of the piston is 1 11/16". The rod numbers are C6AE-C. I'm using the C8AE-H heads and want to come out around 9.5:1 cr. Can anyone tell me what these are and what the cr would be with this set up. I assume (careful here)this was the original set up in this engine. It's in a 73 f100 4x4, but I don't know if it is the original engine.
Senior User
Joined: Aug 2003
Posts: 152
Likes: 0
From: Maple Ridge BC Canada
The dished pistons, are good for about 8.5 to 1..To get 9.5 you will need to run flat top pistons, zero deck the block, and run felpro (or equivalent) .041 gaskets, or run the pistons .015 down the bore and use steel shim gaskets( .020)...Most of the truck heads that I have cc'd run about 73 to 75cc....Should put you really close to 9.5 to 1....D44hd
Cargo Master
Joined: Aug 2000
Posts: 2,931
Likes: 12
From: SW Michigan
piston choice
Tasty, are you certain that the engine is a 390 ? the 4x4 would have come from the factory with a 360, but it could have been swapped. Do you need help choosing some new pistons? DF
Cargo Master
Joined: Aug 2000
Posts: 2,931
Likes: 12
From: SW Michigan
piston numbers
Tasty, how about some silvolite 1131s ? or some 1116s ? or some keith black KB150s ? or some speed pro H304Ps ? Any of those should get you where you want to be. There are some other choices, the speedpro H395P, the TRW 2291F, and the silvolite 1130- all of these are flat, and would work just fine, but might be getting close to 10 to 1. The problem is that most stores (even lots of engine shops ) will try to sell you a set of speedpro 381Ps or a set of silvolite 1139s. Those two part number pistons don't really have anything wrong with them, but they will only give about 7.8 to 1 compression in a 390. Thats not really enough. DF
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