390 Rebuild
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390 Rebuild
I am looking to rebuild my fe 390 (stock). It sits in a 1968 ford f100 and is connected to a c6 tranny that has been rebuilt....no shift kit, no stall converter.
The rear end on the truck is the dreaded 9 3/8, 3.25 gears and 31 spline axles. I'm really just wanting to have a cruiser, but would like for it to make the tires chirp some on the low end. I'm very much a novice but have a friend who is good mechanic and offered to rebuild the thing for me free of charge. Questions I have:
I have read that you can just pull a 9 inch center out of a Ford rear end and drop it into the 9 3/8. I may do this but what gear ratio would I want to be able to spin the tires a little on the low end and still keep my high end.
Or do I need to be looking elsewhere? I know I'd like to change that mammoth cast iron intake out for an aluminum intake, put 4 barrel carb on it, electronic ignition and headers. But what intake, how big a carb etc.....
Thanks
The rear end on the truck is the dreaded 9 3/8, 3.25 gears and 31 spline axles. I'm really just wanting to have a cruiser, but would like for it to make the tires chirp some on the low end. I'm very much a novice but have a friend who is good mechanic and offered to rebuild the thing for me free of charge. Questions I have:
I have read that you can just pull a 9 inch center out of a Ford rear end and drop it into the 9 3/8. I may do this but what gear ratio would I want to be able to spin the tires a little on the low end and still keep my high end.
Or do I need to be looking elsewhere? I know I'd like to change that mammoth cast iron intake out for an aluminum intake, put 4 barrel carb on it, electronic ignition and headers. But what intake, how big a carb etc.....
Thanks
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Joined: Apr 2004
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If you build a decent 390, you will be able to fog the tires with the 3.25s.
I am pretty sure you can swap a 9" carrier into that housing no problem. You would, of course, have to match the axle splines and the u-joint.
For your engine, you do not want "stock" pickup. That gets you a down-the-hole piston with 8ish or worse compression. Go "stock" '66-69 390 GT. 9.5 to 10ish compression, a mild cam, 750ish vacuum secondary carb, Performer intake and headers.
There are multiple--heck dozens to hundreds--of FE builds described in this forum. Scroll down a bit.
I am pretty sure you can swap a 9" carrier into that housing no problem. You would, of course, have to match the axle splines and the u-joint.
For your engine, you do not want "stock" pickup. That gets you a down-the-hole piston with 8ish or worse compression. Go "stock" '66-69 390 GT. 9.5 to 10ish compression, a mild cam, 750ish vacuum secondary carb, Performer intake and headers.
There are multiple--heck dozens to hundreds--of FE builds described in this forum. Scroll down a bit.
Cargo Master
Joined: Dec 2015
Posts: 2,549
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From: Harned, Ky
Dad's old 68 had a Dana 60, my 73 and 78 both had a 9", I wasn't aware they used the 9 3/8" in a pickup.
3.25's are a good all around gear, I've ran them in several different vehicles.
Unless your building a full race engine a 600-750 vacuum secondary is plenty. My 73 had a 428CJ in it that I used a 600 vacuum secondary on and it ran well, in a car I'd have used a 750.
Are you sure you have a 390 instead of a 360?
3.25's are a good all around gear, I've ran them in several different vehicles.
Unless your building a full race engine a 600-750 vacuum secondary is plenty. My 73 had a 428CJ in it that I used a 600 vacuum secondary on and it ran well, in a car I'd have used a 750.
Are you sure you have a 390 instead of a 360?
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Well actually no, it's has 390 badges on the truck and according to VIN that's what it came with new. Why do you ask?? Was there something I mentioned that would lead you to believe it's a 360??
Cargo Master
Joined: Dec 2015
Posts: 2,549
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From: Harned, Ky
More pickups came with 360's than 390's but if it's badged and vin'ed for a 390 that's a good indicator. The engines look the same with the 360 having a shorter stroke but normally had lower compression and less power.
Logistics Pro
Joined: Jan 2011
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From: Antelope Valley ,CA
My 390 Mild build could smoke the peg leg 3.25 with 275/60 15 tires till I wanted to stop . switched to a limited slip 3.55 still babying new rear end for break in but i know she'll still smoke them
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From: Antelope Valley ,CA
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