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Topic: valve seals?

in Forum: C3 Engines


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valve seals? (1/3)
 7/16/14 2:46pm
swany 80vette
Former Member

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Vette(s):
1980 c3


Joined: 3/24/2014
Posts: 62

When I start my vette (350) it smokes a little when first started. Possible its the carb, but not sure doesn't use any oil. It has sat a lot thought maybe it is the valve seals, I replaced a set years ago on a 327 without pulling the heads using air to hold the valves up. Looking for opinions on the smoking and the replacement if that's what you think it is. I know it is hard to tell by not seeing it but looking for some opinions
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Re: valve seals? (2/3)
 7/16/14 5:01pm
HighDesertDave
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Carson City, NV - USA

Vette(s):
Numbers matching 1972 350 4 speed, silver pewter body with blue interior


Joined: 12/4/2013
Posts: 239

Could be seals or more likely guides. How many miles are on the engine? Proper seals will allow some oil to flow into the guide as need for lubrication. Your smoke should be blue if its oil. Brownish/black if its fuel. You plugs may help you determine what is being burned. But, very typical of your cold start smoking would be worn guides. After shut down the guides drip oil onto the top of your piston. Once the oil drains out of your heads the dripping stops. It just sits there on the piston waiting for you to fire the engine and viola...blue smoke. Eventually you will build up carbon which will lead to hot spots, increased compression and pre-ignition. If you don't put many miles on it you may just ignore it until the time is right. 

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Re: valve seals? (3/3)
 7/17/14 10:00am
Adams' AppleLifetime Member
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Duncanville, TX - USA

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


Joined: 11/8/2003
Posts: 20128

A small poof of smoke might not be a big deal.....if it fogs the neighborhood, that's something to worry aboot!
Could be valve guides/seals, sure. One way to check for that is to drive the car on the hiway, then let off the accelerator all the way, and coast down(safely, if in high traffic) until around 30mph or so. Then get back on the accelerator, and look behind you.....if you see a large cloud of smoke, it's the valve guides/seals. If you changed seal before in a small block, it's the same procedure for what you have now. Use the "umbrella" type seals....not the squarish looking ones, or o-rings. Most folks only install seals on the exhaust valves, but I prefer to use them on intake and exhaust. New valve seals will certainly help if you find the problem is that, but if the guides are worn, the new seals are really only a temporary band-aid. Thumbs Up


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