[Son of Magni]

Ok, here's the deal ('72 240, 130,000mi). I'm blowing some smoke.

1) It's not too bad driving at an even speed but if I really get on it, especially after sitting at an idle for a while, it puts out a pretty good cloud. It does not smoke during engine braking.

2) The oil gets contaminated quickly. Pretty black after 500 miles.

3) Consumption is about 1 quart for 400 mi.

4) I checked compression today. #1,2,4,5,6 are all about 145-150. #3 was 95. I put some oil in #3 and rechecked, still 95. Pulled the V-cover and found #3 intake had less that 0 clearance. Backed him off to about 8mils and #3 compression came way up. (Actually it came up to 185 but I think it was high because I had just put that oil in there.)

So here's the questions. I think replacing the valve seals might really clean things up but:

- Is 145-150 good enough compression to suggest rings are OK? FSM says 171-185.

- Is blowing smoke on hard acceleration and not during engine breaking indicative of valve seals or of rings?

- Can bad valve seals cause rapid oil contamination?

Of course, I had hoped that when I pulled off the cover I would be able to inspect the valve seals but through two layers of valve springs I couldn't really see anything...
SoM

 

[yurmohill]

If anyone out there disagrees let me know. i have never seen valve stem seals do squat for these cars. But in your case since you found a valve too tight and after adjustment compression came up i would do the following: 1) torgue head, 2) adjust all valves, 3) change oil and filter, 4) give us a new report after 1500 miles.

 

[luggnut73]

Magni, I have 178k on my '73 and the compression was close to what you found , mine went all about 150 and #5 115 I adjusted the valves and now all are at about 150 with a max spread of 18 lbs.. I have only had the car since the first of this year at least on the road since then. She dosnt smoke or burn much oil , 1qt in 2500 to 3000 depending on how hard I am driving. on the hiway the consumption goes up to the 3 k. I think that your compression is ok, if your fuel mixture is rich that will increase the oil contamination, also some oils tend to get black sooner than others just from heat. In my experiance valvoline and casteroil seem to get black rather quickly. If you are using and not leaking a qt, per thousand you most likely have a damaged oil ring on . Question, is there any of the spark pluggs showing oil fouling, is the ingine at idle smooth ?? If the engine idels roughly , disconnect a sparkplug wire with the engine running and if the idle changes and misses more reconnect the wirer and do the same with the next one, and so on untill you find one that makes little difference and you have found the ciylinder where the problem is.The best of luck to ya , Gary Portland Or.

 

[1970_240z]

son,

i think you fixed the problem already. you say there was 0 clearance on the valve and once you fixed it the compression came back up. that means that the valve was not closing completely, thus creating a leak, thus leading to low compression. the dirty oil could be from combustion gasses gettin ginto the wrong place because of a valve not closing completely. your compression numbers indicate rings that are wearing but not yet in need of replacement IMHO. how does the car run now that you adjusted the valve to spec?