72 GMC Jimmy engine/transmission suggestions

[87Skier]

I got this from my father-in-law. He said he was hauling to the junkyard if I didn't take. He really had to twist my arm, if you know what I mean.

There are some good and bad things about it. First the good is that it now runs and drives (it sat for 17 years without driving, but after changing some fluids, new cap and rotor, carb rebuild, new gas it runs pretty good), second, "light" rust, third, everything is there except the top.

Now the bad, the top is missing, the rockers, floorboards and some of the supports are rotted out, and the engine is not original.

Which brings me to my next point, I can't say I'm a fan of the Chevy 400 motor, and want to switch it to the stock motor, the 350. But, I want to keep it mostly original, but make it more drive-able at the same time, so should I swap in a carb 350 with a 700r4, 4L60 or 4L80 behind it?

Also, I'm planning on doing a body off restoration in the future, but not for a year or so.

Forgot to mention, I don't hate the Chevy 400, but this one was a hack-job. Some one made a custom alternator mount, string is required to keep the radiator hose off the cooling fan, and the water pump/cooling fan are misaligned with the crank.

[87Skier]

And here's a picture of the engine now:

[landy]

If the 400 engine runs good, why not just keep it and get the correct brackets, pulleys, and accessories? Brackets and pulleys should be relatively easy to source. I'd think all the small blocks, the 400 included, use similar brackets, pulleys, and accesories.

While you're enjoying driving it, you could source a 350. Jegs has some great deals on Goodwrench 350 shortblocks. I think there are some posts and links on those deals on the '67-'72 pickup forum.

[Moreyel]

I bought a new GM Goodwrench 'crate' complete for under 2 grand. No core required. If you want, I'll find out the sellers name and get back to you.

[Mike C]

If it runs fine, spend your money on other stuff first. But if you have to have a motor, Jeg's running a sale now. Check thread on main 67-72 board. I wish I could get give-me's like that!

[SamMargritz00]

Ill take that sb400 off your hands! haha, but if I were to do mine again, I'd probly go with a 383 stroker with a 700r4. Thats whats in our black and red chevy 1 ton and that thing is dang impressive for as heavy as it is. I love the newer 5.3/4L60E combo but i kinda miss the old school technology. For a top it might be hard to find one in decent shape. I have one but the soft top in my opinion is the way to go. Just for the fact of ease of putting it up and down with one man instead of a small army.

[Banderian]

Second the soft-top idea. I'll never put that hardtop on again.

[87Skier]

Thanks for all the suggestions!

It seems you guys are just as mixed up as I am. Some of you recommend keeping it, and others say go with crate motor.

If I was going to take the engine out, clean it, and add in a few new parts would I be wasting my money? I would like to clean up the engine compartment, and dress the engine. I'm thinking the entire drivetrain will be coming out when I do the floorboards and fix the rot.

[Reno]

SBC 400 is a torq monster - keep it, or sell it to me!

SBC 350 & 400 are the same as far as brackets etc, the heads in a SBC 400 have steam holes but thats internal….I would have to go check to be sure but should also have the holes threaded in to the heads for accessories….

KEEP the 400! I had one in my 72 3/4 ton pu with a 700R trans and it was the best combo I've had in one of these trucks for every day use….if you go 700R get an earlier one that does not require computer converter lock up.

[87Skier]

That's what I was thinking for the transmission, but after running some numbers I might end up just keeping the transmission. After looking at the tire size, and rear end... the engine should be doing just under 2000rpm at 60mph, (without slip), so overdrive would probably lug the engine.

I think I'll keep the 400, but will probably end up rebuilding it. Its leaking in 3 or 4 places underneath.

[71swb4x4]

If it runs like it is just work on buttoning up the little things. Brackets, fan, radiator hose, etc will have to be fixed even if you buy a new crate motor.
A few leaks under it could be as easy as valve cover gaskets. No matter what it is try to track it down. The brackets, hose and leaks aren't the mark of death for the motor.