EFI PISTONS
Tuned
Joined: Apr 2001
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From: Newbury NH
EFI PISTONS
i just took apart a EFI 460(88)with D9TE block to use the HD rods in my other 460.I noticed the EFI pistons has a lesser dish and just a tad of a valve relief compaired to my other one(D1VE block and D3VE heads)I'm planning on using C9VE-429 heads and the HD rods.If i use the pistons from the EFI will those give me to much compression
Elder User
Joined: Aug 2001
Posts: 508
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EFI PISTONS
For your "mutt" engine, you'll need to measure all the volumes and calculate the CR.
As for the EFI pistons, I think they bump the CR to 8.5:1 compared with the 8.0:1 of carb'ed truck pistons. Ford doesn't like to give CR specs - and the specs I've seen are suspect. I looked up the chamber sizes for 75, 82, and 89. They are virtually the same, except that the 89 is 1cc bigger. There is a 3cc min to max range, so 1cc is nothing. This 1cc is probably because of the smaller intake valve.
So, for the EFI pistons, a smaller piston dish with same sized chambers means a CR higher than earlier 8.0:1. Later 460's ('93 or so) are often spec'ed at 8.5:1. I suspect this spec applies to all EFI 460's.
Ludis
As for the EFI pistons, I think they bump the CR to 8.5:1 compared with the 8.0:1 of carb'ed truck pistons. Ford doesn't like to give CR specs - and the specs I've seen are suspect. I looked up the chamber sizes for 75, 82, and 89. They are virtually the same, except that the 89 is 1cc bigger. There is a 3cc min to max range, so 1cc is nothing. This 1cc is probably because of the smaller intake valve.
So, for the EFI pistons, a smaller piston dish with same sized chambers means a CR higher than earlier 8.0:1. Later 460's ('93 or so) are often spec'ed at 8.5:1. I suspect this spec applies to all EFI 460's.
Ludis
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