rebuilt c1 engine smoking revisted

[Don Izzo]

I had the 283 rebuilt. After about 1500 miles I found I had Broke 3 valve springs which hadn't been replaced on rebuild. Pulled the heads and replaced everything with new: seals, valves, spings, keepers, everything. After 200 miles the car starts to smoke (passenger side head only) only after it has run for 15-20 minutes. NO SMOKE ON INITIAL STARTUP! Smoke is apparent when the engine is reved. Seems to clear up when I back off the throttle at idle. Pulled the plugs and they are clean. No oil on them at all. Disconnected the vacume module to the PG trans. still smokes after 15-20 mins. Did a compression test all cylinders in the head show good compression. Engine rebuilder thinks it's the carb? So I changed out the carb for my spare WCFB and it still smokes. As a side note I have found small dropplets of oil on the rear of the intake manifold top surface and a light film on the face of the distributor stainless ignition shield near the throttle lever bracket. I can't locate the source of this oil leak. It is not the oil pressure switch fitting. Some one suggested the intake could be leaking, sucking oil into one of the cylinders,past the intake gasket but the plugs don't show oil. I am about ready to pull the intake and carb and change them. Anyone have any suggestions?
Don

[Mark B.]

Re: rebuilt c1 engine smoking revisted

Don, Bluish-white smoke out of the tailpipes is oil....grey/black smoke is a carb running too rich....white smoke out the tailpipes is anti-freeze/water. You say the plugs are clean, compression checks out and the smoking starts after 15 to 20 minutes. Are you sure you don't have an anti-freeze/water jacket leak? Head gasket not sealing? After 15 to 20 minutes that cooling system will be under pressure and you could have a leak in one of the head gaskets or intake manifold gasket at the head. The oil film you describe could be anti-freeze blowing out under pressure.

[Mike M.]

Re: rebuilt c1 engine smoking revisted

my first thought runs parallel with marks thoughts---coolant. what kind of head gaskets did the rebuilder use? if steel, did you check torque on head bolts after initial start-up? let us know what you find and good luck, mike

[Don Izzo]

Re: rebuilt c1 engine smoking revisted

I installed the fel-pro head gasket set. They are the no re-torque blue ones, same for the intake. No I didn't re-torque the heads. The rebuilder keeps telling me it's carb but the smoke is definetly blue! I'm starting to think it's something with the intake yet if it is it's on the underside as there is no evidence of a vacume leak around the top side. I tested for intake manifold vacume leak with an unlit butaine torch passed around the intake gaskets. No increase in engine RPM (don't worry this was done outdoors to avoid explosive atmosphere in the garage). What else Can I try?
Don

[Mark B.]

Re: rebuilt c1 engine smoking revisted

Don, Although you installed the Fel-Pro intake gaskets, you should always install sealant around the water jacket passages on both ends of the heads and the manifold passages. The rear crossover is a dummy, but pressure can build there. I'm guessing that you have an internal gasket leak at either the front or rear crossover passages at the head and manifold that is allowing coolant to seep into an intake air stream. Possibly a small leak that re-torquing the intake manifold bolts might cure. I rely heavily on "red" Permatex silicone adhesive sealant when installing gaskets where liquids are present. Good Luck.

[Clem Z.]

the fel pro intake gasket are too hard

unless you have every thing flat to get a good seal. use the stock GM type with the metal insert between the 2 surfaces that thermal heat seals itself to the heads and manifold

[Joe L.]

Re: rebuilt c1 engine smoking revisted

Don------

Oil seeping past the intake manifold gasket in the lifter valley usually will not cause fouling of the plugs. It gets in there at such a "controlled rate" that the plugs usually "burn clean". Over time, though, normal colored deposits will build up on the plugs.

My suggestion: remove the intake manifold and note if there are any oil deposits in the cylinder head ports or carbon build-up on the back surface of the intake valves. If so, you're pretty well assured that oil leakage past the intake gaskets is the culprit.

How to solve it? That's not so easy. One thing, though: when you remove the intake manifold bolts, note if they bind as they are turned out. Also, note if there are any thread marks on the upper surface of the manifold holes. If you note these conditions, you MIGHT be able to solve the problem by slightly elongating the bolt holes in the manifold. If not, I don't know what to tell you.

[Don Izzo]

Re: rebuilt c1 engine smoking revisted

I thank you all for your input. The engine rebuilder stands on his theory that it's the carb. I think that the temp increase coupled with thermal expansion of parts is involved as it only presents after the temp reaches 180 degrees. I am going to pull the intake and attempt to correct the problem here first. It seems like the easiest course of action. Thank you again!

Don