I have a 1979L-48 with a stock 350 and holly 600 on it. I have owned it for a couple of years now and it burns a little oil. The rear bumper above all 4 exhaust pipes is always turning a light shade of black. I had a friend that said the valve seals are probably shot. I have never been that far into an engine, is this something that an average person can do with the corvette service manual? Once I pull the heads, is there anything else that I should replace while I am there. I plan on doing it (maybe) this winter.

The car runs great. Just would like to keep it running as long as possible and I don't want to damage the engine. If I paid someone to give me a valve job, how much do you think it would cost...Virginia Beach area.

 

If the valve seals were bad you would get blue smoke. Black on the bumpers sound more like a carb problem to me. Burning to rich will give you the black soot on the bumpers. Pull out a few spark plugs. If they are black also you might try putting smaller jets in the carb. Very easy job on a holley. Valve seals are a pain to do in the car. You would need a hose that screws into the spark plug hole attached to compressed air to keep the valves from falling into the cylinders when you use the valve spring compressor to take the spring off to get to the seal. Not a hard job just a pain.

 

And dropping a valve is a real PITA. BTDT Finally got it back up using a coat hanger thru the spark plug hole. Couldn't figure out how to use duct tape.

 

I have never done anything with my carb other than put it on my car. I guess it is time to learn about that now. Any help out there would be greatly appreciated.

 

Hey riley
Rebuilding your carb is really pretty easy. It starts with a good rebuild kit. You can get step by step instructions on the internet. I was trying to find the site I used but didn't bookmark it. I'll keep looking and post it when I find it.

 

There's also several good books on Holley tuning available.

 

There is an alternative to the air in the cylinder to hold the valves while replacing seals or springs. Get a bunch of small rope(1/4" or so) Remove the spark plug,run the piston down a ways 1/4-1/2 way down. Feed the rope into the cylinder thru the spark plug hole. When it won't take any more rope gently bring the piston up enough to compress the rope pretty tight. DO THIS BY HAND NOT THE STARTER! After the seal is changed,lower the piston and pull the rope out. Maybe more time consuming than the air thing but 100% reliable! I've dropped valves using air,not a big deal if the piston is at TDC,still scary!
Ron

 

I am still nervous about doing the valves, worried about dropping one. Should I just take the heads off and do it? I have never done that, it sounds exciting though. I took the air cleaner off today and noticed some fuel on top of the carb, no puddles but you can see where it has been sitting. The carb is about 2 years old and only about 2000 miles on it. Do you think it is out of adjustment?

 

I agree with Rich!

Black means running to rich and blue/white means burning oil.

Before you spend and real money or time you shoud first spray some carb cleaner in the carb and dump a bottle of fuel cleaner in the tank.

I would also adjust the two mixture screws on the carb.
Very easy to do. I turn them in one at a time (engine at idle) to the engine wants to quit
running and then back out until the engine smooths out.

Another thing is if you are burning oil you will smell it.


Good luck,
Schoon

 

In a word, no. If you have an air compressor, it's relatively easy to do. And if you're worried about dropping a valve, just run the piston up to top of its stroke on each cylinder before you pull the keepers. If not, then partsman41's rope method should work.

But as others have said, it's more likely gas and not oil.

To check valve seals, have someone follow you and first accelerate briskly and then coast and the accelerate again. If your follower sees a puff of blue smoke when you get off and then back on, it's valve seals.