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Topic: Smoke!! Help!

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Smoke!! Help!

Posted: 11/13/20 6:23pm Message 1 of 18
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Vette(s): 1970 Blue Convertible with pipes and flares

I’ve had the car for 12 years and all along I’ve had a subtle smoke at idle and a little burn of the eyes. I rarely drive it but when I do it rides just fine. With corona keeping me home now, I’ve started doing some things to it I always wanted to do one being clearing up this smoke. Started with a tube up. Rebuilt the msd dizzy, new plugs, wires, msd coil, brand new edelbrock 650 carb, air filter, fuel filter and after struggling a little getting the timing right, the smoke is a lot more evident. I did a compressions check and all came back 200 to 205. Did a combustion leak test and twice and the liquid stayed blue. I’m running out of things to check on. I would greatly appreciate any ideas. 




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Re: Smoke!! Help!

Posted: 11/13/20 7:42pm Message 2 of 18
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Does it smoke all the time?

Is it blueish or white smoke? More input please....😉




Joel Adams
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Re: Smoke!! Help!

Posted: 11/13/20 7:48pm Message 3 of 18
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Vette(s): 1970 Blue Convertible with pipes and flares

Before it did not smoke all the time but since I did all the work it does it all the time. It’s white smoke I believe. Does not smell or taste sweet. The oil smells like fuel a little but I have replaced the carb since that started. I’m getting desperate and may change the oil again to see if that helps. 




Re: Smoke!! Help!

Posted: 11/13/20 8:22pm Message 4 of 18
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Grapevine, TX - USA
Joined: 8/26/2006
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Vette(s): 1972 LT-1 convertible with factory air. 2017 Black Rose Grand Sport convertible.

White smoke could be coolant.




   

Re: Smoke!! Help!

Posted: 11/14/20 12:16am Message 5 of 18
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Overland Park, KS - USA
Joined: 7/9/2003
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Vette(s): 1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day. 2023 Accelerate Yellow HTC Stingray

Blue smoke would be oil and since your compression and leakdown are good,  I suspect the valve guides or valve seals are bad. Valve seals are relativly easy to replace. You'll need a spring compressor and an air compressor with a fitting to screw into the spark plug hole to prevent the valve from dropping down after you remove the keepers.

Valve guides are a different story as they require head removal.  Options are knurling or pressing in new guides. I never felt knurling was a long term fix. 




1973 L-82 4 spd

Re: Smoke!! Help!

Posted: 11/14/20 3:12am Message 6 of 18
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I don’t it’s coolant because it passed two combustion leak tests. 73Shark, is there a way to test to see if it’s valve seals or guides?




Re: Smoke!! Help!

Posted: 11/14/20 8:30am Message 7 of 18
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

A combustion leak test only tests for combustion by-products leaking into the coolant...it wouldn't necessarily show if coolant was getting into the combustion chamber. A crack in the head in certain locations could put coolant into the exhaust stream and not into the combustion chamber, so that could be a possibility.

If it smokes all the time, then you have either oil, or coolant leaking into the exhaust, either from combustion blow-by, a bad head gasket, cracked head, etc.

Valve guides, or valve seal leaks typically leak the worst under a vacuum, such as when you get OFF of the throttle, and the vacuum in the intake manifold is high. This would not be a continuous smoke producer....the smoke would come and go as the vacuum changes. Valve seal/worn guides will also normally show up on a hot re-start, and on cold starts after the engine has been off for some time, but the smoke will dissipate shortly after that....the smoke doesn't stay continuous.

What you COULD have is an intake gasket leak, that sucks engine oil into the intake port(s) while running. That could cause a smoking all the time situation. Hard to test for that, since the leak is on the underside of the manifold. Something to consider....




Joel Adams
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Re: Smoke!! Help!

Posted: 11/14/20 9:43am Message 8 of 18
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Overland Park, KS - USA
Joined: 7/9/2003
Posts: 914
Vette(s): 1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day. 2023 Accelerate Yellow HTC Stingray
Bluesting 70 said:

I don’t it’s coolant because it passed two combustion leak tests. 73Shark, is there a way to test to see if it’s valve seals or guides?



Not that I'm aware of.  Are you seeing any increase in oil consumption?




1973 L-82 4 spd

Re: Smoke!! Help!

Posted: 11/14/20 12:27pm Message 9 of 18
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Vette(s): 1970 Blue Convertible with pipes and flares
73shark said:
Bluesting 70 said:

I don’t it’s coolant because it passed two combustion leak tests. 73Shark, is there a way to test to see if it’s valve seals or guides?



Not that I'm aware of.  Are you seeing any increase in oil consumption?


I’m not. But then again, I haven’t been driving it much at all. I’m planning on pulling the block out soon for bay clean up and paint as well as a few other things.

I appreciate the feedback from all of you. Any suggestions on what I should di while the block is out?  I was considering upgrading the heads. 




Re: Smoke!! Help!

Posted: 11/14/20 3:51pm Message 10 of 18
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Vette(s): 1970 Blue Convertible with pipes and flares

One other thing o meant to mention, it’s dieseling pretty bad at cut off. It’s done that before but much more now. 




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