Evaluating a running engine with potentially conflicting information

I posted a question about this last week and got no replies, so asking again. I’m considering purchase of a 1990 Dodge in order to harvest the running 3.3 L V6 engine. The car is otherwise junk with a dead transmission, so it’s headed for the crusher, thus for sale cheap. My question is whether the good compression test results override some other signs I noted on the car. My compression test showed 145-160 all around, and the engine started easily, ran well, and sounded good to my somewhat experienced ear (no timing chain noise which I know well on this engine). Oil looked normal, no sludge and it was not black. So far, so good.

However, the car seemed to have been abused, and I’m not sure how significant those signs are. The signs include a serious dent in the oil pan, no coolant VISIBLE in the radiator, oil everywhere on the top and front of the engine, plugs uniformly black, bald tires, and a beat up interior. Each of these can be interpreted as being insignificant…the oil pan was not punctured with NO sign of a cobbled patch job, radiator could have been just a bit low, oil was definitely leaking from the front valve cover-easily correctable, and the black plugs might just have been a bad O2 sensor or something similar.

It’s the coolant which concerns me most…I wish I had filled it from a measured container, but that didn’t occur to me at the time. If the coolant had been low enough to overheat the engine (it lives in a hot part of California), would that show up in the compression test? Could a head become warped or a head gasket be compromised, and not yet be reflected in the compression? Could there be other problems lurking that I’m not considering? Given that all I need is a good block and heads and don’t care about the fuel system, A/C, electronics, etc, does the compression test give me reasonable assurance that this engine is probably ok?

Thanks for any advice!!

You should pass on this because the engine is half worn out. Compression is already on the downhill slide and if you go back and perform a wet compression test you are probably going to see those 145-160 readings go up to 170-190, etc. This means a piston ring problem.

Yeah OK4450 has the right idea… As to your coolant question…if there was no or very low coolant… the head gaskets could have been compromised long ago… ALL of the other items you described are telltale signs of serious NEGLECT if not outright ABUSE… Can the engine survive these things? Suprisingly YES they can…but…why risk it?.. When you do an engine swap you either start with a known good engine or a new or rebuilt one…the reason for this is because you have a lot of work invested in this project after you go about pulling two engines and installing one…so the need to start with a strong foundation is only logical… Asking for us to guess as to the health status of this engine is a moot point…it could be fine despite obvious abuse and neglect…or it could be toast. Why gamble? There are better ways to go about this… saving on a cheap engine purchase may just bite you in the end costing you more than if you just spent more on the known working engine foundation…

Ask me how I know… Trust me with as many years as I have been doing this I have made almost ALL the mistakes and bad decisions that you are about to, or thinking of, making… Been there done that… Thats why when the “boys” on here give their opinions…it is best to pay attention. Collectively we have like well over 100 years of mechanical experience here…its best to heed our FREE advice

As for your question about compression numbers…yes it is possible to post good Psi numbers and still have head gaskets that are not WATER tight… SO… Go with a better donor engine before you undertake such a big mechanical project. Its only logical…

Thanks gentlemen, I appreciate your good advice. I did pass on this donor vehicle engine at first, but have kept thinking about it. You’ve put my thoughts to rest. I had hoped to go with a reman engine, or rebuild the engine I’ve got, but the recipient vehicle just isn’t worth the cost of that, even with a pro mechanic doing it as a side job for less $.