If it can be fixed easily then fix it. If you're looking at a rebuild or new I would go new crate engine and never look back. Truck looks like it's worth the extra cost to go new. I put a GM crate engine in a 79 GMC short bed years ago and it was the best choice I could have made. I had the engine rebuilt (454) in a 98 3/4 ton suburban and it was a total nightmare- never did run right-ended up trading it in on a different truck and regret it everyday. That being said- I know the rebuild was totally the fault of the mechanic but I'll never go down that road again.
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I'm no help with the truck but what type of grass do you have in your yard?Comment
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This is making me think you’ve got bad valve seals/seats, and the PCV valve is stuck, which forces oil into the exhaust and is burned off or head gaskets are shot and leaking past.Originally posted by FamousAmos View Post
Bad exhaust valve seats would look like low compression since the valves wouldn’t seat all the way and pressure leaks past.
Bad valve seals on the intake side would allow oil to leak into the chamber and burn off, valve job may be all it needs. I had a 94 Z71 that did this and would use about a quart every 1-2k miles, that one ended up getting bored and stroked with a nasty cam setup, and I think back then was about $3500 or so to get it done, of course that was 16+ yrs ago.Comment
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I install Jasper Engines at my shop and for piece of mind it is the only way to go with their warranty. The price you are quoted is fair for that. But I agree with other posters that that motor should not have that type of problem at that miles. If it was taken care of I would think the worst it would need is a valve job. But if you are going to keep it and since you just had the transmission rebuilt I would do the motor. That motor retails for $2700 plus around 10 hours labor and any extras like plugs wires hoses ext.Comment
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Had a 97 just like it in tan till some maniac in Reynosa totaled it while parked out in front of the plant on hwy 2...me, I would probably rebuild with just a few extra ponies.Comment
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I'm betting stuck valves. I'd put some heads on it and let her sing.Comment
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Some good advice here. The first thing I'd do is run a quart of rislone in it and see if that helps anything.Comment
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Thanks a whole lot. I will take it into another mechanic to get a second opinion.Comment
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I have a 91, with the 350 in it. I rebuilt it myself at 165,000 and cost me about 800 bucks. Thats way high i think, all i did was put on new rings, rehone the cylinders, all new gaskets and get the heads checked and freshened up. It still runs strong to this day and has cold a/c. LolComment
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On the subject of head gaskets, if someone tries to tell you that, you have to have water in the oil or oil in the water for there to be a head gasket leak. That's not true. I have seen hundreds of leaking head gaskets maybe 50% of the time, there is water in the oil or oil in the water. If the gasket blows between two cylinders you likely won't have any water in the oil or vice versa. And you likely won't have any over heating problems either.
The very first blow head gasket I ever found, was when I was in school many years ago. Someone brought in some old Chevy with a small block in it. No over heating, no oil in the water, no water in the oil, no over heating problem. It had a dead cylinder and what sounded like a bad exhaust leak. The driver's side head gasket blew out the rear of the engine, sounded like a blown exhaust manifold gasket. I was feeling around with my hand trying to find the leak, it sounded like it was coming from the back of the engine. I stuck my hand behind the back of the head, the hot gases blowing out the back of the engine, got my attention, when I stuck my hand back there.
I have found many head gaskets blow between two cylinders, the only symptoms were dead cylinders.
To have less than 80 psi on a cylinder, you have a very serious leak. Things that will cause that low of compression are a broken piston, not very likely in a stock engine unless the pistons are from the 70s or older, or cheap, Mexico or some other source of very low quality piston. That or the engine is making a lot more power than stock, or the ignition timing is way off. Breaking a ring land and piston ring, will cause the compression to be that low, but again, it would probably take a situation such as the engine making a lot more power than stock, or the ignition timing way off.
Other things that will cause that low of compression are blow head gaskets, or the valves not sealing. Valves not sealing to that degree, would be a bent valve, which would typically be a result of over revving a engine and floating valves, to the point, that the piston hits the valve. Or a broken valve spring. if a spring is broken, the valve may not fully close, and the spring pressure will be much lower than it should be, which would allow for valve float at much lower rpm than with valve springs in good condition. Broken valve springs are not that common, more so on two cylinders of a stock engine.
Other things that can cause a valve to not seal, would be something getting trapped between the valve and the seat. Most commonly would be carbon, that or something left in the intake manifold. Or by some freak of nature, something went up the intake hose to the air cleaner, got past the air filter, then down in the throttlebody, very slim chance that would ever happen. If the source of the low compression, is valves, I would guess a bunch of carbon got broke loose from some place and went down two or more intake runners, and wound up in between two of the valves and seats. That's possible but for two cylinders to be that low on compression, I would suspect gasket blown between the cylinders. A gasket blowing in that way, typically won't put any coolant in the oil or vice versa. And it's pretty common for small block Chevy's to blow head gaskets.
The other possibility was the flat cam lobe idea, like I said, that should have a roller cam, which would have a very low chance of a cam lobe or two going bad. But it's possible. Small block Chevy's are one of the worst engines for flattening cam lobes, when they have flat tappet cams. If the engine was from the early 90s back, it could have a flat tappet cam. If it had a flat tappet cam, then the possibility of a bad cam, is very high. More so, because you or whoever has been changing the oil, most likely has not been putting zinc in the oil. If you don't put zinc in the oil, with a flat tappet cam, the cam lobes will eventually get eaten up. If it's a small block Chevy or big block Chevy, probably very quickly. The small block Chevy, big block Chevy and the Ford 2.0 and 2.3 L SOHC old iron headed engines are some of the worst for cam lobe failures, when they have flat tappet cams. When the manufactures started using roller cams in the mid 80s, that greatly reduced the number of cam failures with the small block Chevy's, big block Chevy's and the Ford 2.3 SOHC engines, the Ford 2.0 SOHC was long out of production by that time.
The engine in that truck is a Vortec engine, I am pretty sure 100% of them had roller cams. But you might do some research on the subject, I could be wrong. It is also possible that you have collapsed lifters, which will cause the valves to not open fully. Depending on if it is a intake or exhaust lifter or failed cam lobe, as to what will happen. If you have a cam lobe or lobes go flat or collapsed lifter or lifters. You will get a lot of lifter noise, or valve train noise with either type of problem.
If anyone tears into that engine, have them clean or replace the EGR valve, because those commonly got carboned up. Then make sure they sure they replace the plastic tubes in the intake manifold that run from the injectors to the intake ports, those commonly leaked. GM had a cheap strange fuel system on those engines. Where Ford's cheaper fuel system, was to use 8 fuel injectors with only four injector driver's in the computer, then fire four injectors at a time. That system is called batch fire injection. The computers are cheaper, since you don't have as many injector drivers in the computer. GM's cheaper system only used two injectors like a throttle body fuel injection, but they had little plastic tubes attached to the bottom of those two injectors, so when each injector fired, it sprayed fuel in four cylinders. It was a cheaper way of GM getting a batch fire fuel injection system. They only used two injectors and two injector rivers, to Ford's eight injectors and four injector drivers. Those little plastic hoses would leak fuel after time, so you did not get the proper amount of fuel in all eight cylinders. With the mileage on that truck I would have those replaced when someone does whatever gets done to the engine.Comment
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Thanks!Comment
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I would get a second opinion. Unless you 100% trust the mechanic. If it is indeed a total failure. Replacement with the 100k mile warranty is hands down the route to go. Rebuild if you are able. A true quality rebuild will eat you up in labor with minimal warranty. Unless... you have a quality machine shop in town with the 5.7L units ready to go. I have 435K miles on my 98. Original engine. Multiple water pumps and 1 trans rebuild. I drive it on 14 hr road trips 5-6Xs a year. Pulling boats, campers, racecars you name it. I also travel deep into Mexico to the ocean. Several times a year. Mileage is a number.... taking great care is important. I've seen abused 5.7s with way more miles than yours. Where are you located? I don't mind checking it out.
Side note.... I am a GM master and ASE master tech. Not that mean a hill of beans. But I don't mind helping.Comment
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i have a 97 chevy c1500 extended cab too, and i swapped the engine after it overheated and warped the block. I got the engine from a salvage yard, $600 delivered to the mechanic, and then $1000 labor to do the swap. Engine still runs great, although the transmission needs to be replaced now.Comment
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