390 to 302?
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Senior User
Joined: Mar 2009
Posts: 460
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From: New Oxford, PA
390 to 302?
First off- don't get excited! I'm not switching anything over. I'm just looking at all possible options. I like 302's because you can do so much with them, they're readily available as are parts. I love the 390 and FE's, but I'm thinking of trying something new- just seeing my options here! Also- I have a Supercab, so that's one thing to remember...
Alright- just say I wanted to switch my 390 over to a 302 or 351w. What all do I need?...
1. Will/can a 302 bolt up to my c6 tranny? Or would I need an adapter, or a small block c6, or just go with a c4?
2. Engine perches- was the deal there? Where/can I get them? Would ones from a newer pickup work? Like the ones from 80 to 96? What's compatible with my '76?
3. Driveshaft- would I need a custom one? Or would one from a 80-96 Supercab work? Depending on what tranny I uses of course.
I know a 302 sounds wimpy in a Supercab, but they did it in the 80s and 90s with no problem. Although my truck is probably heavier.
Opinions/help/suggestions.
No "rebuild the 390, screw a 302" mumbo jumbo- I'm just brainstomring and seeing what my options are. Just looking for technical info.
Alright- just say I wanted to switch my 390 over to a 302 or 351w. What all do I need?...
1. Will/can a 302 bolt up to my c6 tranny? Or would I need an adapter, or a small block c6, or just go with a c4?
2. Engine perches- was the deal there? Where/can I get them? Would ones from a newer pickup work? Like the ones from 80 to 96? What's compatible with my '76?
3. Driveshaft- would I need a custom one? Or would one from a 80-96 Supercab work? Depending on what tranny I uses of course.
I know a 302 sounds wimpy in a Supercab, but they did it in the 80s and 90s with no problem. Although my truck is probably heavier.
Opinions/help/suggestions.
No "rebuild the 390, screw a 302" mumbo jumbo- I'm just brainstomring and seeing what my options are. Just looking for technical info.
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Joined: Apr 2004
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1. Trans won't work. Try an AOD so you can run a shorter gear and still have reasonable revs. Or a C4. FE bell pattern is different than 302.
2. 302s were sold in '76s, right? Later ones from 302 or 351w trucks might work, might require adapting.
3. You'll have to figure that out after it's installed. Got a two piece job in there now?
Remember cooling, electrical, accessory drives, exhaust.
2. 302s were sold in '76s, right? Later ones from 302 or 351w trucks might work, might require adapting.
3. You'll have to figure that out after it's installed. Got a two piece job in there now?
Remember cooling, electrical, accessory drives, exhaust.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
IF you think a 390 with a 2bbl drinks fuel, wait until you underpower the same truck with a smaller motor 
If it were me, I'd at least go for the 351W because of the stroke. Or even better, stroke the 351W.
What is your ultimate intention for the swap? Better mileage? More power? What?
If it were me, I'd at least go for the 351W because of the stroke. Or even better, stroke the 351W.
What is your ultimate intention for the swap? Better mileage? More power? What?
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
I think a 302 is going to be just awful in that truck. They are underpowered in 1980's f-series trucks and your truck is 500 to 1000 lbs heavier. Can you say DOG?
If you're going to go through the trouble of swapping a motor in there, go with a 460. Or just build the 390 so you can keep your trans. Dropping a 302 in there would be at the bottom of my list.
If you're going to go through the trouble of swapping a motor in there, go with a 460. Or just build the 390 so you can keep your trans. Dropping a 302 in there would be at the bottom of my list.
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Senior User
Joined: Mar 2009
Posts: 460
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From: New Oxford, PA
Yeah- screw the 302 idea. I was only considering it because someone I know has a rebuilt 302 he's trying to sell, which he'd sell to me cheap.
I would rather rebuild my 390.
cripes- what the hell was I thinking! sheesh! A 302 for a 390, HA!
I would rather rebuild my 390.
cripes- what the hell was I thinking! sheesh! A 302 for a 390, HA!
Lead Driver
Joined: Jul 2007
Posts: 7,868
Likes: 9
From: Rhode Island
302s are good little engines in lighter trucks and cars and be quite potent, but once you get a 302 built up enough to make the kind of torque and power you'd want in a big heavy truck, you might as well have just built up the 390. Plus, pushing a smaller motor harder can really decrease its life.
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