My 1998 Dodge, 5.2 engine/AT, 115,000 Mi

Recently took the vehicle to a shop after the “Check Engine” appeared, it had low compression on one cylinder, they pulled the heads and a crack was discovered between the valve ports, after a new head and dressing of the old heads valve seats,new spark plugs & air filter, picked it up, but it still has a slight bucking when i’m driving ~40 mph in fourth gear and I apply slight throttle if I start up a grade,I noticed this when driving before with the CE light on and thought they were related, took it back to the shop, they checked it out, replaced the ignition wires, with no improvement, the mechanic now belives it is the transmission converter, he added a additive to the transmission to try that out, TRUE or BO-O-O-OGUS

There’s not enough info known to make much of a guess.
Fuel pressure been checked?
Any codes present and if so, what?
What does “dressing” of the valve seats mean? A proper valve job or an amateur, bench top lapping with compound?

You state it had low compression on one cylinder. People routinely post on this board with low readings that they claim to be good and even an annoyingly large number of shops are misguided in this area.
Maybe you have 7 cylinders that sucked and one that sucked even more. It would be interesting to know what all of those readings are.

Cracks between ports are often caused by severe and/or chronic overheating. If this has been the case then I would really want to know what those comp. readings are and the possibility that this cylinder head job was a waste of time/money is at least plausible.

I do not think the fuel pressure was checked, the mechanic did not mention it in his report, however, I have no problem maintaining +70 mph, before the heads were pulled, with the CH light on, he checked with his instument and found no problems, and continuing to diagnosis the problem, did a compression check, cylinders 1-7 were ~90 lbs. #8 ~ 15-20 lbs. I purchased this vehicle new and it has never-ever overheated, the heads were sent out to a machine shop for grinding the seats where they found the crack with some product they use for checking, they ordered the new head and when they were delivered back to the shop, my mechanic showed me the crack in the old head.

Just to clarify something, are you saying that these compression readings were taken AFTER the cylinder head work?
If so, you’re in trouble because 90 PSI falls into the sucks (badly) category much less the cylinder with 20 PSI.

If those readings were taken BEFORE the cylinder head work then a wet compression test should have also been performed at that time to determine if the valves were the cause or whether it was the piston rings.
It would be highly unusual for a 115k miles Dodge engine to suffer low compression across the board due to cylinder head valves/valve seats.

The compressions were taken before the heads were pulled, in the past when compressions were taken with a hot engine, now, don’t they recommend allowing the engine to cool before removing the spark plugs and compressions may be lower with a cooler verus a warm engine ?

There may be a little variation between a hot and a cold engine but it’s not enough to worry about or to influence any diagnosis.

While I’m not privy to what the mechanic was thinking during the diagnosis procedures, I will say that when readings like that were obtained at the start a wet compression test should have been done immediately due to the red flags going up.
A wet test means that a small squirt of oil is placed into each cylinder and the compression rechecked. If the number goes from say 90 up to 140 or whatever then the piston rings are at fault.

Actually, a crack between a couple of valve seats would have no influence on how an engine runs unless the valve seat(s) were loose or deformed. Even then that would only be on the one cylinder. Many Subarus were prone to cracks between the seats and the cylinder heads were completely useable.
I’ve built a lot of Subaru engines and replaced a large number of head gaskets while reusing cracked heads. It’s never been a problem although I do not like the practice. Even Subaru at one time stated the heads should be reused.

Just my opinion but I think a compression test should be run again, both dry and wet, to see what comes up. Since your truck is aged and has comparatively low miles on it the problem could be due to sludged up piston rings.

A rule of thumb is that the cylinder compression numbers should be about 20 X the compression ratio at sea level and varying with barometric pressure.
So a 9.1 compression ratio X 20 would yield about 180ish plus. Subtract a small amount for wear, altitude, and baro pressure and you should still be seeing 175ish on a good engine.
I hope some of this helps.

I will retake a compression on my own with my screw in compression guage and also a wet test, also, this vehicle has only used that synthetic “ONE” oil, changed every 7000 mi and is burning one quart between changes.