198 compression question

[upthepunxx]

i have no compression on cylinder 4... erratic compression on all, ranging from 40 to 120... whell i bought the car, it had been stored for about 10 years, then a fellow college kid bought it, ran it for seven months without oil change or any maintenance (drove to burning man and back like this!). Then i bought it for $150.00, the timing was alll the way the opposite of good! carb was not adjusted at all, the 1st cyl. had a leak in the exaust mani.
What i have done: Oil change +filter, wires, plugs, tires, adj. carb. replaced pcv valve, flushed tranny, replaced vacuum hoses, fuel filter and fixed the mani. leak.
ran it about 3000 miles with 10W30 Wt. oil. i can stick my hand at the end of the tail pipe and get unburnt oil spatter. 1 quart a week added. gonna try 50 Wt. oil after next oil change... im thinking rings, or maybe a bent or stuck valve. weather hasnt permitted taking the valve cover off yet. does anyone have any other ideas? not new to cars just new to this Mopar stuff. Thank anyone in advance for replies!
:newb:

 

[moe7404]

here is a long shot. if the trouble is in the pistons, and it might be that, try marvel mystery oil, in the gas. use 4 oz in 10 gal of gas. i have been using it for over 30 years. in your case it might take a month or two. just my idea. but it will not fix a damaged engine.

 

[memike]

cam or valve adjustment could be a problem here, I don't know what year model eng you have, plus if the /6 sat and he had thin/burnt oil on it the exhaust system may be contaminated with oil... set valves and do what
the poster before me said and drive it and see if this clears up if the rings are not
toasted, valve seals and guides could be sucking oil in from the top to the piston.

 

[Dartnut]

Do a leakdown test to the engine and you'll find out your problem right away.
Switching to 50 weight oil won't really achieve anything except cause more strain to the oil pump.
I honestly think you are looking at a rebuild or replacement of the engine here.
The good news is you can pick up good used slant 6 engines for cheap these days!

 

[BillGrissom]

Make sure that your compression test method is OK. Best to remove the spark plug tubes and use a screw-in gage. An old "press-in" gage w/ the tubes in place is asking for erratic readings. If you get the Harbor Freight kit like I have, you can easily connect an air hose in place of the gage and apply 20 psi w/ the piston at TDC and search for the leak. You will hear and/or feel air flowing out of the crankcase (bad rings), intake (bad I valve), or exhaust (bad E valve).

In my experience, if the rings are truly bad, you will have a lot of blue smoke. If the valves are so bad you don't get any compression, raw gas will flow thru and your spark plugs will be perfectly clean looking. Using a vacuum gage while idling is another way to check valves. If the needle jumps wildly, that can indicate a bad valve.