390 pistons
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From: south east Nebraski
390 pistons
putting a 390 in a '64 3/4 4X4, and have tore it down. Motor still is in OEM bore spec. Pulled pistons, and it appears I have a frankenstien. I won't get into details... but do have a question. I have found that the ring grooves in the pistons are smaller on 7 pistons. My ring set fits one piston. Are there different sized piston ring grooves on the 390's? I've done a little shopping around, and cannot find this "other" size ring..... I can do more, was hoping you guys may know where to look.
currently running rings groove size 5/64, 3/32, 3/16
currently running rings groove size 5/64, 3/32, 3/16
Last edited by RxRF250; Dec 10, 2020 at 03:11 PM. Reason: forgot spec sizes...
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What is the compression height of the pistons? Close to 1.77" or 1.66"?
I can move you to the engine forum, or you can look for 390 build there, whatever you want.
Do you have the engine mounting figured out?
Back to the 390. The piston ring size might have changed through the model years and by application. Are you going to reuse those pistons?
What kind of build are you going for?
Pickup 390s are built with a sunken piston for low compression. Car 390s are much closer to the deck.
I'll check back.
I can move you to the engine forum, or you can look for 390 build there, whatever you want.
Do you have the engine mounting figured out?
Back to the 390. The piston ring size might have changed through the model years and by application. Are you going to reuse those pistons?
What kind of build are you going for?
Pickup 390s are built with a sunken piston for low compression. Car 390s are much closer to the deck.
I'll check back.
Lead Gopher
Joined: Aug 2012
Posts: 10,067
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From: Seattle
Here's an example of a 1/16", 1/16", 3/16" ring groove 390 piston. Ford made a change to a 3/32" second ring groove in 1968 I believe it was. Not sure about the other grooves and how they changed.
FORD ICON Performance Pistons IC862-040 ICON Premium Forged Pistons | Summit Racing
FORD ICON Performance Pistons IC862-040 ICON Premium Forged Pistons | Summit Racing
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New User
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From: south east Nebraski
Ill move this to the engine forum.... didn't see that.
no idea on compression height. its a true frankenstien. Pistons from 4 different motors. I've already got it mounted and in place in truck. Was trying to get it going, When I discovered multiple issues. Was told it was "golden".
Been a long long story, as i have too many other projects.....
thanx guys...
no idea on compression height. its a true frankenstien. Pistons from 4 different motors. I've already got it mounted and in place in truck. Was trying to get it going, When I discovered multiple issues. Was told it was "golden".
Been a long long story, as i have too many other projects.....
thanx guys...
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