1979 C10 5.7 Diesel advice
 

I bought a fairly clean rust free '79 C10 Scotddale with an OK running 5.7 diesel motor. It needs a trans rebuild but engine seems to run fine.
I plan on doing a body on restoration. My question is-should I ditch the 5.7 Diesel and go 350 gas (or LS)? I've heard bad things about the 5.7 "Oldsmobile" Diesels. I've also heard many were replaced with the "DX" replacement diesel that has a better rep. How do I tell if mine is the original 5.7 Block or DX? AND- would I be better off to scrap the Diesel and just go Gas? Thoughts? Thanks

Re: 1979 C10 5.7 Diesel advice
 

I'd offer it up for sale to see if there is any interest in it. Somebody might have a mint Diesel Cadillac that needs one of those engines. If it runs well and lasted this long I would be tempted to keep it and drive it.

Re: 1979 C10 5.7 Diesel advice
 

If the trans was good, I would vote to run it until something broke. But with the need for a trans rebuild and your plans for a restoration, I would swap in a new motor and trans combo and 2nd the thought on trying to sell the diesel to someone that really wants one. Better to get the drive train the way you want it before the pretty pretty paint is finished.

Looks like a good body in the pic.

Re: 1979 C10 5.7 Diesel advice
 

Keep it. It's unusual and original.
The DX block has DX cast into the sides down around the freeze plugs.
It has updated injection pump, updated heads, larger head bolts, longer main bolts and, roller camshaft.
If you want overdrive get a TH200R4 with the diesel torque converter.

Re: 1979 C10 5.7 Diesel advice
 

If you decide to repower, think about what you like.

If you enjoy figuring stuff out, tracing wires, hours of online research, tuning and adjusting on a computer; then go LS.

If you're only happy if you have a wrench in your hand, consider wiring a necessary evil, want to quickly button up the project and go, then install a SBC.

Edit to add: There's a lot more info available for the gen 3 ls motors, and less complication getting them set up compared to the gen 4's. I'm struggling through a gen 4 swap, and am sorta' wishing I'd have found a gen 3 instead.

Re: 1979 C10 5.7 Diesel advice
 

The motor mounts are setup for an Oldsmobile engine. An Oldsmobile 307Y or 350 Rocket is a drop in replacement for the 350DX. You can use the 307Y HEI distributor in the 350 Rocket.
If the DX is running why get rid of it?
The early diesels are unusual and the ones that made it this far are likely just fine. Everyone has a smallblock or a 454. Not everyone has an Oldsmobile in their squarebody.

Re: 1979 C10 5.7 Diesel advice
 

I can't see any "DX" markings on the side of the block. It does have "GMD3A" on the driver side of block. Would that be the original block? I can't find much when I research it. Thanks

Re: 1979 C10 5.7 Diesel advice
 

The 350N used Stanadyne Pencil injectors that clamp onto the heads. You'll see a tube straight up from the injector and a tube on the side with a fitting over the side of the valve cover IIRC. It's been a long time since I saw a 350N.
Attachment 1954487

The DX engines used Lucas micro Poppet injectors that thread into the heads.
Attachment 1954485

Re: 1979 C10 5.7 Diesel advice
 

I'm thinking it's the original block then. Thanks for the knowledge.

Re: 1979 C10 5.7 Diesel advice
 

I'd be looking for a 403 or a 455

Re: 1979 C10 5.7 Diesel advice
 

The Oldsmobile 403 has windowed main webs and it was made at the peak of the 70's emissions era so the power potential is limited.
The 455 Buick Olds & Pontiac engines don't like higher RPMs. They're different mills but the BOP 455's all have long strokes so the rods like to escape out the bottom when you wind em up.
I dropped several rods out the bottom of the 455 in my 73 Bonneville wagon when I was 17 because I was beating the heck out of it driving at high RPMs. I put a 400 Pontiac in place of it and that put up with my foolishness.

This is why I suggested the 350 Rocket. It's a noticeably higher torque mill than the smallblock 350. Even the Oldsmobile 307Y has pretty decent torque for the displacement because the bore to stroke ratios of the Rocket engines are setup to produce enough torque to push those big Oldsmobile land yachts around. The 307Y bore is large enough that the valves aren't shrouded like the smallblock 305. GM used the 307Y in the late 80's boxy Chevy Caprice wagons for that very reason.

The DX was installed as a Goodwrench warranty replacement.
The valve covers would have a big GM Goodwrench sticker like the TargetMaster gasoline engines.

The earlier 350N truck motor with pencil injectors had slightly more HP and torque than the DX.

Re: 1979 C10 5.7 Diesel advice
 

I daily drove my olds diesel for about 8 years. It never ever let me down and I averaged 18-20 mpg while doing it. I also had a T400 with a gear venders behind it, so the 4th gear helped a lot. I also didn't ask it to do anything I knew it couldn't. These diesels were made strictly for fuel mileage and that was it. 125hp, 250 ft.lb. torque. That's all you get. Don't do anything with you wouldn't do with a V-6 gas motor.

I'd run it until it dies and then perform your swap. In the meantime, you'll get a lot of people with a confused look on their face when you pull up to the diesel pump. Haha.

Don't forget that if you swap to a gas engine, you'll have to really clean those tanks out or replace them, as they've had diesel sitting in them for 40 years.

Re: 1979 C10 5.7 Diesel advice
 

Advice?

Rip that boat anchor out and replace it with something proper. Anything.

Re: 1979 C10 5.7 Diesel advice
 

I put a factory high compression 455 out of a 1968 olds 98 years ago and loved it! Bolted right in.

Re: 1979 C10 5.7 Diesel advice
 

The easy swap would be a 1976 or earlier 350 Olds - nice long flat torque curve! A 455 would burn tires at will - if that is what you want. You trans and motor mounts are currently set up for an Olds (small or big block) and to change it to a Chevy would be a lot more work. 1977 and later Olds blocks are light weight castings and windowed webs so you would want the 1976 and earlier "Rocket".

Re: 1979 C10 5.7 Diesel advice
 

The 350 Rocket is a beast. Nothing like the smallblock Chevy 350. I had one in a 1970 Delta 88 with a Rochester Quad on top of a cast Iron olds intake. I installed a later Olds HEI distributor on it in place of the points to cut down on fussy maintenance chores.
Those 1960's and very early 1970's Olds engines were torque monsters.
It moved that big land yacht like the Devil himself had his cloven hoof on the gas pedal.

Re: 1979 C10 5.7 Diesel advice
 

Now that was worth signing in for!

Re: 1979 C10 5.7 Diesel advice
 

Just me? Keep the Diesel. Getting scarcer and scarcer... only 1779 made with the C10 in 1979 Less than 600 in 80 & 81, For all original trucks I've seen prices up to $17,000 and A collector bought one with 8,600 miles near me for $14,000 from a older guy i knew in MI...

Pros: Great fuel milage, Doesn't need serviced a lot like a gas, Sounds kinda like a Cammed gas with good exhaust, and Something different.

Cons: Doesn't make HP like the Gas, Certain parts are harder to find, Only came in 2WD.



Save a Survivor!!!

Re: 1979 C10 5.7 Diesel advice
 

If I found a good 5.7 diesel in a decent 79 or 80, I would drive it as long as I could before I put a gas in it. I like them.

Re: 1979 C10 5.7 Diesel advice
 

I drove my 81 Buick Estate Wagon with a 5.7 diesel in it until the diesel refused to start one day. Then I dropped in an Olds 455. I never regretted it.

Re: 1979 C10 5.7 Diesel advice
 

Love your signature. Man after my own heart.

Keep the diesel OP. Enjoy a rare bird for awhile before you put in an engine that everyone on earth has. And they do sound wonderful, a nice lope at idle.

Here is a link to what mine sounded like with Thrust welded mufflers:
https://www.youtube.com/watch?v=cBr0...ature=youtu.be

Re: 1979 C10 5.7 Diesel advice
 

I'd devise a plan for what you want to do when the diesel goes kaput, and then wait. If it never goes kaput, then you won't have wasted your money on a swap. If it does, then you'll be ready! Nice looking truck AND camper shell!