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Engine rebuild or swap considerations

eodcoduto

eodcoduto

We could have been closer.
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I’m on an all day work meeting so I’m doing important work things like thinking about the future of the Suburban.
1991 V2500 with the 5.7, ballpark 200K+ miles since the OD doesn’t work. It doesn’t use oil, has some odd TBI quirks but is my daily driver and I put 200-300 miles a week on it. I pull 7000lbs a few times a year and need to be able to go cross country with a 2 hour notice.
I’m a planner and budget driven guy so I see it needing a power plant in 2 years, and I want to get things in order.
My thoughts are:
- Rebuild and keep the 350 TBI with some reliability and small torque improvements.
- Swap in another engine and go with an aftermarket EFI.
- Swap candidates are a 350, 400, 292 6cyl, 427-454, 400 Pontiac, 455 Buick, Olds, Pontiac.

All have pro’s and cons and a LS/LT or Diesel won’t be considered mostly due to cost and the number of nickle and dime parts needed.

Fire away!
 
Yea the 350 is probably getting 10-12 now, I need to log some miles with my gps to see for sure. 454’s are easy to find too, I would need to see about swapping computers to tune it right. Having the 4l80 is nice.
 
You can get a 350 rebuilt unit for decent money, cheaper than building one for sure. That ultimately will be your least expensive route.

You already have a pretty bulletproof EFI system that as long as you got go crazy like putting a huge cam in the fresh engine the stock EFI wi continue to run just fine.

I’d take the time to refresh the Tbi unit and make sure the throttle shaft bores aren’t worn out causing a vacuum leak. But the money saved on aftermarket EFI or other engine would be put to use getting a quality rebuild done on the 700r4 with key upgrades added to it.

I agree with Wes though, cubic inches would make things easier when towing. A Tbi 454 while not fast will do the job better but will run off if your stock system with an updated prom. Or you go to an aftermarket EFI system with it.

Going big block would require redoing the exhaust since the manifold outlets don’t land in the same place. Fuel delivery would be no different unless you upgraded to aftermarket EFI.

I still think your most economical route would be fresh Tbi 350 and go. It won’t set the world on fire but it will be way better than a worn out unit. You might look at bumping the gearing a little deeper to increase torque depending on your tire size too.
 
I dont think I would go aftermarket efi on that truck tho, it seems that there is always issues with the aftermarket, while oem injection has quirks after 30 years but still does decent.
 
The TBI gets the job done and mine is worn out, I’m going through it to get the idle smoothness back. So many choices and I like having all of the different experiences to see what fits my needs the best. Tires will never go above 32”, and it has 3.73’s in it.
 
eodcoduto said:
The TBI gets the job done and mine is worn out, I’m going through it to get the idle smoothness back. So many choices and I like having all of the different experiences to see what fits my needs the best. Tires will never go above 32”, and it has 3.73’s in it.
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I’m betting some of the idle quality or lack of it would probably be the throttle shaft leaking past the base plate. Totally common and I went through an outfit in Florida on a customer’s Tbi to get a full rebuild on. They redrilled the baseplate to fit with bushings for the throttle shaft to ride on on top of the full rebuild work over. I don’t remember the name for the place as it was a few years back.

With 32” tires and 3.73’s I don’t know that I would go through the expense of changing gears. 4.10 is so close and 4.56 would be too much. If you had 3.42’s I’d say do it but I wouldn’t with 3.73’s.
 
I don’t plan on changing gears or axles, the sole focus of the suburban is my daily driver and farm vehicle, with inspiration from PMA4x4 and some expedition portal builds.
 
My 01 is big block 8.1, and 3.73.
get 12mpg consistently on hwy. Even towing @3k current tire size is 245 75 16
 
I like stupid and simple. I just ordered a new TBI from SPR performance, bored to 46mm and set at 13psi. My throttle shaft has a leak, and 32 years out of the original isn’t bad.
 
No way to be 13psi out of the box . Pumps make each 1 act differently. So need a guage to know for sure .
 
They build them and bench tune them, setting the regulator to 13psi. I’ll put a new vortec pump in and should be good.
 
The order fell through on that throttle body but before replacing the base gasket, depinning the IAC connector and replacing it, cleaned IAC, etc it was at 12.8mpg. After those fixes and replacing the drag link and tie rod ends and an alignment I’m just over 14mpg, the replacement engine is still on the burner but I’m like a 14 year old me trying to make an adult decision.
 
As long as you aren't constantly angry at the power levels of the 350, to me it seems a no-brainer to keep it running as long as you can without mods.

Gradually save up for its inevitable replacement. I'm sure many have gotten well over 200k out of these motors, but generally my thoughts are that by then they are starting to use oil, leak oil, and will need work sooner rather than later.

There is still significantly less expense/hassle to keep it TBI SBC vs even BBC.

The other engines in consideration would be for novelty, not practicality, which doesn't scream daily driver to me. Don't want to start an argument, but the SBC and BBC in this day and age are going to be cheaper and easier to deal with (cheaper parts, more choices, etc), hands down.
 
I know from experience you do not want to rebuild one of these TBI GM engines because the heads are crap, and they all crack eventually from old age. The blocks are good for rebuilding, but the heads once they have about 200,000 miles on them they are junk. You can either buy a complete GM Goodwrench replacement 350 TBI crate engine, or you could rebuild the block, then get a set of Edelbrock TBI replacement heads that will live longer than you will. If you have that kind of budget. A Goodwrench Gen V 454 crate engine (which is the engine your truck would have had come with if it had a 454) is nice if you have that kind of money. You would have to do some reconfiguring of things like sensor wiring, accessory and belt routing, and a few other things if you went 454. The OBDI/ECM you have should run a 454 because those where all the same across the two different gas engine choices your burb could have come with.

There is a company on the east coast that can do a killer rebuild job on your TBI. I cannot for the life of me remember what company that was. I had my TBI rebuilt and modified by a guy named Vic Morse, but he passed away about a year ago, and is no longer in business. Here are some pictures of my GM Goodwrench TBI new 350 crate engine I installed some years ago on my 1991 V3500 crew cab along with my rebuilt and modified TBI. My crate engine has about 15,000 miles on it, and runs like a champ.

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I think Vic Morse died and they shut down the business. This engine now runs good, leaks some oil but doesn’t use any and gets the job done. My quest for power would be geared towards 350-400ft-lbs of torque for pulling a trailer, and I don’t see 4500+rpm ever happening. A short block with some aluminum heads from summit would fit the bill. So many choices, but torque is the goal and 14+ mpg.
 
eodcoduto said:
I think Vic Morse died and they shut down the business. This engine now runs good, leaks some oil but doesn’t use any and gets the job done. My quest for power would be geared towards 350-400ft-lbs of torque for pulling a trailer, and I don’t see 4500+rpm ever happening. A short block with some aluminum heads from summit would fit the bill. So many choices, but torque is the goal and 14+ mpg.
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The only problem with low price aluminum heads from Summit (or anywhere else) is that they are angle plug heads. You cannot use cast iron manifolds with angle plug heads. You can only use headers, and even with headers it is going to be a PITA getting spark plugs and wires to fit right. The Edelbrock aluminum swirl port heads are the only ones that are straight plug heads. They are expensive at about $800 a piece (maybe more now with inflation). Those heads are swirl port replacement heads with bigger valves than stock swirl port heads. The problem with stock heads are that they only have a deck thickness of 1/4", which is why they crack after a lot of miles. Aftermarket heads deck thickness is 1/2", and will never crack.
 
The problem in your situation is TBI. There is no way around that issue without replacing it or digging into reprogramming.

A Vortec SBC or BBC unquestionably makes more power. But neither of them is a direct swap that isn't going to add additional cost and work to what you already have to do with the engine itself.

And if you are to that point, then you might as well consider LS, because how much more work will it actually be?

Nothing wrong with RPM's to make power if you've got the transmission gearing to tame it down on the freeway. See: Overdrive transmission.
 
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