Your opinion on seldom driven GMC V20

[Steve1987]

Greetings,

I have a 1987 GMC V20 that I use to plow our 800ft drive and occasionally pick up lumber or gravel. I might put a 1,000 miles on it annually. It has a 5.7 tbi engine that has begun burning massive amounts of oil. I want to keep the truck and replace the engine. I have been behind the dash and the wiring is poorly spliced together and just cut in places. The port for diagnostic test does not work.

My understanding is I can use any tbi engine through 1995 but, will need the computer box from the same year as the engine. I believe the original truck wiring harness (as poor as it is) can be used. Should I stick with a tbi engine or would a carbureted engine be an option? Thanks.

Steve1987

 

[Goldie Driver]

I am not a TBI expert but would assume so long as you reuse any sensors you have currently and do not use any extras you may find on the replacement motor it would just be a drop in.

Which is why I would also say stick with the TBI - you have it, and it will make the task a bit simpler.

Any diagnostics on the oil burn ?

For example , is it a stuck ring that a little Seafoam, Marvel Mystery Oil, and some good ol blow out the carbon romping, stomping, and daily driving might fix with luck, or is it just worn out?

Best of Luck !

Britt

 

[Vbb199]

If its a 5.7 tbi motor you're replacing it with, I don't think you need another ECM unless you're like.... going from smog to non smog or something.

The 4.3, 5.0, 5.7, 7.4 with or without an auto or manual are all a little different I think in terms of parameters, but if it's just another 5.7 tbi motor, it should just go right in with no issue.
The 4.3 I believe is its own tbi.
The 5.0 and 5.7 I think are the same tbi, different injectors.
The 7.4L is a different tbi, with bigger injectors.

I might be a little off on this info, but you shouldn't really have to change your ecm for another 5.7

 

[dvdswan]

Before assuming you need an engine, as @Goldie Driver said, diagnose it first. Does it smoke on start up and then go away after warming up? I would use it more often than you do now and see if symptoms change or fix themselves.

1k a year is babying the truck and does not do seals/gaskets any favors and can dry/rot out. I would make it a point to drive the truck at least 2 weekends a month (about 100 miles each weekend).

 

[Bextreme04]

Greetings,

I have a 1987 GMC V20 that I use to plow our 800ft drive and occasionally pick up lumber or gravel. I might put a 1,000 miles on it annually. It has a 5.7 tbi engine that has begun burning massive amounts of oil. I want to keep the truck and replace the engine. I have been behind the dash and the wiring is poorly spliced together and just cut in places. The port for diagnostic test does not work.

My understanding is I can use any tbi engine through 1995 but, will need the computer box from the same year as the engine. I believe the original truck wiring harness (as poor as it is) can be used. Should I stick with a tbi engine or would a carbureted engine be an option? Thanks.

Steve1987

You won't need to use one specific to your year. Any 350 from 87-95 will bolt right in if you reuse the TBI and sensors from your current engine.

As others have said, I'd maybe try troubleshooting a bit more to see if you actually need a new engine. Compression test and leakdown test will tell you health of the engine and cylinder heads/valves. You might just have a stuck/bad PCV, or a bad intake manifold gasket, or a bad transmission modulator. Are you sure you are burning engine oil? Is it just on startup or does it smoke all the time? If all the time, you might just have a stuck ring... maybe just seafoam and an Italian tun-up would clear it right up.

 

[Steve1987]

I had the truck looked at a year ago for lack of power. The mechanic had told me the engine was worn out. But, for all I used it for, it could last several more years. Between adding oil and poor performance I just decided to make a change. I looked at upgrading to a newer model used truck, but the prices are just rediculous. Steve1987

 

[John-Ryan]

Before assuming you need an engine, as @Goldie Driver said, diagnose it first. Does it smoke on start up and then go away after warming up? I would use it more often than you do now and see if symptoms change or fix themselves.

1k a year is babying the truck and does not do seals/gaskets any favors and can dry/rot out. I would make it a point to drive the truck at least 2 weekends a month (about 100 miles each weekend).

X2 on this

 

[Matt69olds]

The only way I’d replace a engine on a vehicle I drive a 1000 miles a year is if it wouldn’t run. Sounds like this one runs, just smokes. The limited use might be a big part of the problem.

Remove the PCV valve, make sure it rattles when you shake it. Reinstall it, start the engine. Pull the breather from the other valve cover, put a piece of paper over the hole. Engine vacuum should hold the paper in place. Make sure the breather in the valve cover is clear and not clogged with crud.

Next thing I would try is taking it out for a long hard drive. If you have a trailer hitch, find the biggest heaviest trailer and really work the truck. You might find the oil consumption/smoking is just because the engine is carboned up.

 

[AyWoSch Motors]

Personally I'd carburate the thing, get rid of the TBI, but that's just me. Any 87-95 TBI 350 will swap right in no prob.
If you use all the same sensors and injectors and such, your Computer wont know the difference, relatively easy swap. I'd also look into just rebuilding want you have, for 200 bucks in rings and gaskets, you can have your same engine back to new specs, assuming there's nothing terribly wrong with your old block or heads.

 

[Grit dog]

If it’s not weak and doesn’t leak, I’d keep pouring the oil in it. Unless it looks like a mosquito fogger going down the road. Good time to try some snake oils to reduce consumption imo.
But to answer your question, yes up to 95 is 100% plug n play long block. Idk about the jewelry on top.

 

[peats]

Poor performance slowly coming on can possibly be a worn cam or timing chain. Happened to me. I don't know if you have a roller engine but the chain could be the problem.

 

[Steve1987]

The mechanic says the engine has a 14% average leakdown on the test. If I keep the truck, he suggests a used engine.

 

[Matt69olds]

That not really not all that bad, especially if it leakdown is even across all 8 cylinders. Was the engine warm when he did the test? If not, the results warm will probably be better. The upper limit for leakdown is 20%.

What’s more important than the actual number is where the leak is coming from.

I bet if you really work the engine hard, and run a leakdown test again, you will see improvements. A engine that only gets a 1000 miles of use has got to be pretty gummed and carboned up.

 

[Rusty Nail]

Yeap I wanna vote for the old "blow the cobs out of it" plus add gratuitous amount of MMO in the oil AND the gas.

You got one of them piston rangs flipped upside down. They got a word for it...it's uhh

Eggy Weggs...

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[Grit dog]

I missed the fact you said it was also weak.
Fwiw, I drove the hell out of a weak 350, plowing snow commercially plus being a DD for about 8 months straight. It never did give up the ghost just got weaker.
Sold it running and driving. Truck wasn’t worth putting an engine in for me.
Point was I put probably 15k miles or more on it in that time. For you that’s a lot of years. Run the cobwebs out of it and see if you can’t free up the rings would be my first go to.
Then I agree with your mechanic. Used engine