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So, I have an 89′ Suburban 2500 with the 350 and Turbo 400. i used it as a daily driver for obo a month and then it developed a miss. It ran fine before, no smoke, knock, or anything. Then, it developed a ping more like a knock. So I replaced the distributor and cap and wires etc. Still didn’t fix it. So i did a cylinder compression test and 4 and 6 are 40 psi. The others are between 150-160 psi. I think it has burnt valves. My question is, is it worth putting new heads and etc on it or getting a junkyard 350 or 454? If I put new heads, i would like to go with vortec heads. Engine only has 96,000 miles on it but was a plow truck. Would like to know what you guys would do in my situation.
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You could run a wet compression test to verify if the problem is in the head or in the block. Though, i suspect you’re right about it being the valves. A 350 with 96k miles isn’t too bad. I’d say it has plenty of life left in it.
If it was in the block, wouldn’t the gases be released as blow by? I don’t have any blow by or oil consumption. But it wouldn’t hurt doing a wet compression test. But what I would like to know, if it truly is the head, should I throw heads and etc on it? If I do that i feel i’d have to do the opposing side as well because that could be on the verge of going too. Or just get another used engine? 350’s at junkyards running usually go for $500 around here.
If you can get a low mileage 350 for $500, do that. While you’ve got it tore apart you can change the rear main seal and oil pan gasket much more easily because they are probably leaking by now.
Unless the failure is catastrophic, I’m always inclined to fix what you have rather than dropping another used engine into the vehicle. I don’t trust junkyard engines because they come with a history that is entirely unknown to you. To do the job right, you’d have to completely disassemble the donor engine, inspect and measure all the important stuff. No sense diving into a new can of worms when the engine under your hood can be fixed.
I’ve seen junkyard engines people have picked up, which obviously have been sitting for an extended period of time, and these folks wound up having to deal with rusted rings and bores, and other nightmares. In almost every case, it would have been easier and cheaper to fix their original engines, rather than farting around with another engine that was a turd to begin with.
In your case, I would suggest a leakdown test. By listening and determining where the source of the compression leak is, you’ll have a good idea of what to expect when you take things apart.
The place I would be gettin my engiine gives a 30 day warranty where if it blows up or anything, i can get another one.
When it comes to a SBC 350, everybody has their own take on it. If you like rebuilding things and have the time then I’d say Evil-I is right that it would be the surest way. But if you’re just wanting to turn the project around real quick and don’t have a lot of time then a quick low budget engine r&r is good too. Little more risk but you can mostly mitigate that by replacing all the gaskets. Doing that, you’ll have a pretty good idea of what you bought before you drop it in.
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