tacmale

I know about the blow by problems with these motors as they age. My question is what is the main cause of this.

Is it the cylinders or a bad or weak head design.

With the car running you see alot of blow by when you open the oil fill cap.

MagicRat

Blow-by occurs when the partially-burned combustion chamber gases leak past the piston rings. The amount of blow-by usually depends on the condition of the cylinder walls and the design and condition of the piston rings and piston.

By definition, the head is not involved in blow-by.

Even the best engines have some blow-by. Generally engines with some wear have the least amount of blow-by. Worn or scored/scratched cylinder walls, worn rings, rings with end gaps that are aligned, and/or worn/cracked pistons all can make the blow-by worse.

Except for some defective 2.8 engines that AMC/Jeep got in 1984, the 2.8 does not have any worse blow-by problem than many other engines out there.

If your engine produces a steady flow of gases out the oil cap when running at idle, it probably is just well-worn.
If the gases come out in big puffs, like an old steam engine, you may have one defective or badly-leaking cylinder. Such really bad leaks are often not just worn rings. It can be caused by a cracked piston, cracked head or a blown head gasket.

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tacmale

Just as i though was getting conflicting comments from people, but seeing as the engine has 276,000 on it i figured it was the cylinders.

MagicRat

You can't reasonably expect any more than that on an original engine.

I had a '91 Sonoma with a 2.8 and about the same mileage. It ran fine, but had some blow-by too.

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tacmale

LOL i know the motor is on borrowed time but it still runs good just has no power is all. This post has answered one of my questions. I have heard so much bad about the 2.8 I was beginning to wonder if it was worth putting a new motor in. The body is in perfect shape only one small dent in the tailgate.

oldblu65

If you can replace the motor yourself and save the installation costs and the rest of the truck is in good shape , it makes a lot of sense to do so . You should be able to find a good 2.8 L engine at a reasonable price .

MagicRat

Most of the negative comments about the 2.8 are nonsense. It is an very reliable, long-lived engine. Your own vehicle is proof of that.

The biggest 'problem' with the engine is that most of them are a little underpowered.

Since 1980, GM has made both 110 and 135 HP (later 140 hp) versions, in both FWD and RWD configurations.

The vast majority made were the 110 version, and often, this engine simply did not have the beans to power anything other than a J-car (Cavalier) with much authority.

IMO the 135 version should have been the only one made. It was much better, yet got about the same gas mileage and was no more expensive to make.

Unfortunately, the 135 version was only available in the Citation X-11, Camaro/Firebird and the Fiero.

In fact, the lack of decent power lead to a problem in pre-1985 engines. People had a tendency to rev these engines regularly past 5000 RPM in an attempt to get more power. They would eventually spin bearings (often the #5 rod bearing) due to excess revs.

GM added larger bearings in mid-1985 to correct the problem. IMO if they had used the 135 version there may not have been a problem in the first place.

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Get out of tree....... Stand Tall....... Walk around .......Grow big brain....... Shed fur.......Flee animals....... Make tools.......Chase animals....... Make fire....... Invent politics.