My 87 iroc L98 with 59k on it is smoking at odd times. I thought if any of you have areas to check I would appreciate the advice.


Here we go.. When purchased a year ago, the car smoked at startup both cold and hot. I did replace the valve stem seals and PCV valve, I seafoamed the gas and oil and cleaned everything out.


Now, it smokes only on a hot restart and or if its sitting Idling. I pull up to a stoplight and within 20-30 seconds it will start smoking a bit. When I step on the gas, it puffs a bit of smoke.


I tried putting it in low and revving up to 3500 - 4000 rpm and letting off with the engine building max vacuum, it doesn't smoke when doing that or when getting on it with wot.


What are other potential issues? Injectors, rings, vac, etc.? Any ideas, all I can think of is pulling plugs and doing a compression check to find a weak cylinder? Would like to exhaust all options prior to pulling the engine for a rebuild.


Thanks for the help!

 

Sadly, a lot of SBCs do this. It is most likely a valve seal problem in your heads. They are known to dry out, and allow oil to drip into the combustion chamber. It does it on starts as it has had time to let oil drip down.(same thing on idling (add in the fact the oil is thinner because it is hot)

http://www.summitracing.com/parts/FEL-SS72527/ are a trusted part # to use on them. I am using them on the intake and exhaust.(I am putting some on my 85 Iroc heads soon as I am experiencing a similar issue.)

Another thing I will say that could be a cause is buildup in the head (sludge) near the oil drain backs in the back of the heads. If they are stopped up, oil can't flow out of the head and it will low the path of least resistance(which is down your valve).

The other thing people will worn you about checking is the valve guides. They are easy to check by just seeing if the valve has any side to side movement.


Just pull a valvecover, look at the seals, sludge, and check the valve. I bet you will find your culprit and can avoid pulling that engine!
Hope this helps!

 

Did the valve seals a month ago along with springs. The valve train was very clean, 0 sludge buildup. Used those valve seals too. I suppose aside from a compression check there is no other way to eliminate the cylinder rings as the issue?

 

As a quick old school test, drive your car down a long hill, if possible, with your foot off the gas to create a high vacuum condition. Now, when you step on the gas, does it smoke noticeably? Yes? You feel confident in the valve seals? Then probably rings, but a compression test will verify. GL!

 

Did the smoking "change" any when you did the valve seals. More/less, etc?

Not saying you did them incorrectly, but if you had bad valve seals, then installed them incorrectly, then the issue would stay the same.

 

Not sure, got the car last fall and didn't drive it much. Did the seals this spring before the snow melted. Ill just have to do the compression test then rebuild if I have a weak cylinder. If not, ill pull the heads and have a machine shop rework them. Is that the best approach?

 

If you have a y-pipe you might learn if it's one side or the other or both by running open exhaust manifolds for a bit while you force the problem to happen.

 

i wouldn't use these on exhaust cause exhaust valve get hotter than intake and it needs lube in the guides it gets lube from oil splashing on it the seal keeps oil from leaking past when shut off .. so dont put positive seals on exhaust the intake gets cooled and lube from the intake charge plus oil in intake charge not good