jeep6981

91 rs 305 tbi smokes some on start up then goes away but if i let it idle for say 15 or 20 mins or so she starts to smoke then if i give it some gas it smokes up the parking lot so is it valve seals or piston rings i just bought the car 3 months ago has only 96439 miles on it and in that time i have replaced the fuel pump front brakes sway bar links 2 front tires and a water pump any help would be great thanks

five7kid

iTrader: (14)

Valve stem seals. They get hard and crack (especially when using petroleum-based oil), and let oil down the stem. Extremely common with small block Chevys.

91interceptorZ

iTrader: (3)

valve stem seals (or know as valve guide seals) stock chevy are o-rings..if you replace them...get a set of umbrella seals....like from fel-pro.....probaby won't hurt anything with a little smoke...

jeep6981

how would i know if it was the rings i dont wanna do walve stem seals and it wind up being rings ill sell her b4 i put rings inher

91interceptorZ

iTrader: (3)

I don't know the exact test...but you don't have that many miles so I don't think it's rings (my car went 190,000 before rebuilding..looked real good internally)......but your descriptions of your symptoms describe exactly what bad valve guide seals act like...also chevy seals are just little o-rings..when you compare them to the umbrella style ones....you'll wonder how they even seal at all....also they do get hard and briddle....I would bet you a hundred bucks that it was the valve stem seals...

84Z28406

I'd bet his 100 bucks that it's valve stem seals as well.

chas0218

Do a leak down test. If its the rings are bad the test will prove it. If leak down is good then it needs seals.

91interceptorZ

iTrader: (3)

I don't know why I didn't think of that....

1989IROC-Z5.7L

iTrader: (2)

If you remove the oil cap while the engine is running, it will blow smoke out really bad (most of the time) if the rings are bad. It will most likely have lower compression than normal also.

If it smokes for a couple of seconds when you first start the engine, or while driving you let off the gas and get back on it and it smokes for just a second, most likely its the valve stem seals.

You might want to check your pcv valve (located on valve cover) to make sure it is working right. Also check the air filter.

Hope this helps!

UNCLE TOM

iTrader: (1)

almost positive it's valve stem seals . all above info. is good . when i changed/replaced seals on my 89 i used both umbrella and stem seals . i know , overkill . the seals are cheap , so what does it hurt ? i will be doing it soon on my 91 when i put 1.6 roller tip rockers on . you may also want to consider new valve springs , i am . most important IMHO , is to make sure drain holes on lower front & rear of cylinder heads are clear . sludge build up can slow oil draining back down to crank case . good luck .