Thread: '94 350 replacement/upgrade

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Hi all,

I currently have a 1994 Silverado with a 350 that I inherited from my grandfather. It's got 100k miles and recently started having some issues. Long story short, my mechanic is recommending an engine replacement. A friend of mine told me I should think about getting a slightly newer engine while I'm at it, maybe something 1996 or newer with OBD-II. I mentioned this to the mechanic and his response was "no, everything is different, that won't work." He recommends just buying a rebuilt engine, one that his friend conveniently has available.

So I'm wondering who's right here...I understand the wiring harness would need to be changed, but what kind of other changes would be necessary in order to get a newer 350 in there? Any help would be greatly appreciated.

Thanks!

First question is "how much are you wanting to spend on a 1994 truck?" Putting an OBDII engine in it would be pretty expensive and would offer little advantage over what you could install that is non OBDII.....OBD (on board diagonistics) monitors the sensors and reports conditions that are out of range for the event. Why do you need it?

You could install an el cheapo rebuilt engine...or rebuild the existing engine. Either would reuse the existing fuel and electrical systems.

You could install a GM crate motor....a true "crate engine" not a rebuilt engine that is mistakenly called a crate motor. The GM engine is all new. There are many versions to fit the cost and horsepower needs of the buyer. If your existing truck is a TBI truck, you can install a carbureted engine relatively simply....you need to add a fuel pressure regulator to drop the fuel pressure to 6psi or so. Do a search for GMPP or GM performance parts and see what they have. Summit sells GMPP crate engines I think.

I would recommend not buying an engine that the mechanic is pushing unless you can have an independent third party look at it closely....The mechanic seem to be looking out for his buddy with an engine for sale....not necessarily in your best interest.

what kind of issues???

Originally Posted by robot

First question is "how much are you wanting to spend on a 1994 truck?" Putting an OBDII engine in it would be pretty expensive and would offer little advantage over what you could install that is non OBDII.....OBD (on board diagonistics) monitors the sensors and reports conditions that are out of range for the event. Why do you need it?

You could install an el cheapo rebuilt engine...or rebuild the existing engine. Either would reuse the existing fuel and electrical systems.

You could install a GM crate motor....a true "crate engine" not a rebuilt engine that is mistakenly called a crate motor. The GM engine is all new. There are many versions to fit the cost and horsepower needs of the buyer. If your existing truck is a TBI truck, you can install a carbureted engine relatively simply....you need to add a fuel pressure regulator to drop the fuel pressure to 6psi or so. Do a search for GMPP or GM performance parts and see what they have. Summit sells GMPP crate engines I think.

I would recommend not buying an engine that the mechanic is pushing unless you can have an independent third party look at it closely....The mechanic seem to be looking out for his buddy with an engine for sale....not necessarily in your best interest.

The OBD-II would be a "nice thing to have" if I have the choice. I'm willing to pay more for this feature, but I'm not trying to create any headaches for myself. I had looked at GMPP last night, and it seemed that the cheapest 350 they have starts at around $2000...and that's probably a bit more than I'm willing to spend just to get the thing running right now. Thanks for the details and the tip on having someone else look at the suggested swap.

Originally Posted by jerry clayton

what kind of issues???

Yeah...didn't really want to get into that, but here goes: oil pressure was gradually dropping very low, intermittently, especially while at a stop. Topped off the oil which seemed to fix for a couple of days, then gradually got worse than it already was. Final day of operation I started hearing a knocking sound, so I stopped driving it and towed to the mechanic. I started it up on a cold morning at the shop and it was clacking very loud. Mechanic drained the oil pan and cleaned the screen. Said that he wanted to replace the cam shaft and bearings..at first. Then came back and said that he didn't want to charge me hundreds of dollars to change that stuff out because he couldn't guarantee that it would last 2 months or 2 years. That's when he suggested an engine swap.

I'm with Jerry - what are the symptoms? 100K is not a lot of miles if the truck has been well cared for with regular oil and filter changes.. It's a lot of miles if it's been neglected.

Can you give us a bit more info?

Vortech 5.7 ( '96-'99 ) but use your computer controls, and a vortech 4bbl intake with a TBI adapter ( 454 truck will have that ). that's a pretty common swap for a little more HP

Thanks to everyone for the input so far. I posted a reply to Robot and Jerry earlier but it looks like the computer ate it.

I'll try to recap:
@robot: thanks for all of the detailed thoughts. My preference is to not spend a boat load of money right now. The idea of gaining OBD-II is just a "nice thing to have" while I'm considering pulling the engine out for possibly a new one. I'm leaning towards a rebuild...those GMPP crate engines look great, but I think that will be pushing it in the cost department, considering the idea that trans and/or drivetrain could still go kaboom at any point. Thanks also for the idea of having a pro look at the engine my mechanic's trying to sell me.

@Jerry & Glenn: Here goes: I started intermittently losing oil pressure, especially when idling. After a couple of days of that, I checked the oil, saw it was a little low, and topped it off. That seemed to fix it for a couple of days, but it started degrading again. It finally started a bad knocking sound that made me afraid of hitting the gas at all...oil pressure was dropping to zero, but with plenty of oil. Towed it into the shop the next morning, and on starting it, it was making an awful racket of knocking. Mechanic said that he recommended possibly changing out cam shaft or worst case changing out engine. A couple of days later he said that changing the master bearings might be necessary. Then his final word to me was that he didn't want to do all of that work and charge me 700-800 bucks only to face the possiblity that in a couple of months I might come back saying that my truck was broken again...he recommended just swapping out the engine with one that's already rebuilt.

Like I said, the truck was my grandfather's and I have to assume he took care of it while he was around. He did use it for a while towing a third wheel camper a few times per year, mostly in-state. Unfortunately, the truck sat around unused for 2 or 3 years between him using it and me getting it back in June and I know that's not good.

@Matt: The thing is, I told the mechanic that I wanted a 96 or newer 350 and he told me that the Vortec is what's in his truck, and it wouldn't work because "everything's different." I'm not questioning you in saying that it's not possible, I'm just wondering realistically how much work it's going to be and what type of traps I might be setting myself up for in the future.

test post, 3rd try after computer eating up two long posts

Originally Posted by muntz

test post, 3rd try after computer eating up two long posts

Moderator note: New users need to have posts approved before they show up.



Bill S.

Bill, thanks for the note. My apologies for assuming, but I didn't know whether this was a problem on my side.

What has the mechanic quoted you for engine and labor to do the work. Is it compatible with your truck? What is the condition of the replacement engine? Is it low miles? wrecked vehicle? Will he warranty the work using that engine? Have you had him do work for you before?

Originally Posted by sfort

What has the mechanic quoted you for engine and labor to do the work. Is it compatible with your truck? What is the condition of the replacement engine? Is it low miles? wrecked vehicle? Will he warranty the work using that engine? Have you had him do work for you before?

I'm being quoted $1000 for the already rebuilt engine, $500 for labor, and it's the mechanic who's told me it's the right one. I have no idea about where it comes from prior, but I'll get a 1 year warranty. This guy's done work for me in the past, and I trust his work so far.

At this point, the idea of using this other engine is a variable I'm liking less and less. I'm starting to lean towards rebuilding my current engine and now I'm wondering if there are any parts that I want to be "very involved" in selecting...

Originally Posted by muntz

@Matt: The thing is, I told the mechanic that I wanted a 96 or newer 350 and he told me that the Vortec is what's in his truck, and it wouldn't work because "everything's different." I'm not questioning you in saying that it's not possible, I'm just wondering realistically how much work it's going to be and what type of traps I might be setting myself up for in the future.

the engine blocks are pretty much the same. the '96+ Vortech's have roller cams and probably the best cast iron heads GM ever made for the 350... all you need to do is put all the TBI sensors in the vortech block, and the TBI distributor.. GMPP makes a TBI Vortech intake, and a 4bbl Vortech intake, and the 4bbl intake is cheaper, and a TBI adapter that GM used on the 454's probably runs $15-20 at a junkyard but there probably available new also... if you visit any of the Chevy truck sites, you will find the Vortech heads are a common swap for the TBI engines but the engine itself will work just the same.... using the entire fuel injection from the Vortech would not be very easy as it would take donor wiring from a '96+ truck just to make it work