HT4100 4.1, 4.5, 4.9 Discussion, my 4.1 compression numbers in Cadillac Engine Technical Discussion; I had my mechanic use a good MAC Tools leakdown compression tester that I picked up on eBay. Here are ...
Automobile(s): Cadillac 78 Seville, 78 Coupe de Ville, 92 Sedan de Ville
Re: my 4.1 compression numbers
If you're an optimistic type of guy then you could hope the exhaust valve is just carboned up; possibly from too much octane. I would put some Seafoam in it and take it for a nice long ride and flog it a few times. Other than that just drive it. Peace.
The motor runs fine but it does have some minor secondary problems. Anyway being a 4.1 w/ 140k miles it is at the end of its expected life--even if the cam is still round and the intake is solid, it still has the two dozen other design flaws that are going to contribute to hard failure, and the exhaust valve on #2 obviously needs to be dealt with.
I'm not replacing it right away (my Jeep engine w/ 336k miles is in really bad shape), and I am looking forward to being to take money out of this 4.1 instead of dumping money into it.
My parents got 260k on their 1987 Deville with a 4.1L. It still ran fine with that amount of mileage on it. My 1988 Eldorado with a 4.5L has a couple of leaky valves which causes a rough idle but it has only degraded a small amount after 40k miles. It now has 240k on the odometer and if I do anything to it, I'll put in a lower mileage 4.9L.