1972 LT-1 OIL SEAL PROBLEM/ENG DIAGRHAM

[STEVE MUELLER]

DEAR SIRS

I have recently bought a 1972 LT-1 with 27,000 miles. The car is a complete original. when i got it home this week, I noticed that it was burning very rich, and additionally that there was blue smoke coming from the exhaust. I had two people look at the car and they felt that it was the valve seals, and that the carb needed to be rebuilt. When I took it down the road it ran excellent and had no loss of power, My question is was this a common problem with the LT-1 motor, also could there be another problem for the smoke?or does any one have any ideas!

I would also like to know a est of what it could cost to fix these two problems. also would anyone know where I could get a picture an original motor that I could get so I could use it as a template when deatailing the eng. compartment. thank you steve

[Shane G.]

Re: 1972 LT-1 OIL SEAL PROBLEM/ENG DIAGRHAM

It was unclear from your post whether or not the blue smoke is produced on startup or also while driving. A usual indicator of bad valve seals is the blue smoke at start up only and not during normal operation. Bad valve seals let oil get run down the valve stems and accumulate in thr combustion chambers where it is ignited on startup and shows itself as blue smoke. After a short period of operation, the oil is burned off and the blue smoke stops. If the smoke persists, I would look to worn rings or other internal causes.

[Michael W.]

Re: 1972 LT-1 OIL SEAL PROBLEM/ENG DIAGRHAM

Steve,

The problems you mention are not unique to an LT-1, but they would be unusual on a car with only 27,000 miles. Is it possible that the car actually has 127,000 miles? If it is 127,000 miles then it might be time for some major engine work.

Probably the best thing to do initially is to have a competent garage do a full analysis/tune up on your car. Things like a compression/leakdown test, carb and timing tests and adjustments etc. may do a world of good to help pin down the exact problems.

If you are looking for documentation on your car, most of it is available from the NCRS office.

Mike


Quebec NCRS Chapter

[Robert C.]

Re: 1972 LT-1 OIL SEAL PROBLEM/ENG DIAGRHAM

Steve, Congradulations on your L-T1. You now have one of the truely great sharks. Usually all 28 year old low mileage corvettes need a carb. rebuild after sitting for most of it's life. I agree with the last post that I would get a good recomendation from other Corvette owners for a top mechanic to check out your car. The most help I got for my LT-1 was Dobbins 68-72 V ette Vues Fact Book. There are great Black & White + color photo's of your LT-1.engine/ body etc.Please plan to bring your LT-1 to an NCRS event this year. I,and I'm sure alot of my friends would love to see it.

[Joe L.]

Re: 1972 LT-1 OIL SEAL PROBLEM/ENG DIAGRHAM

Steve-----

Intake valve induced oil contamination of the combustion chamber is a VERY common problem on small block Chevrolets. Until 1981, all small block Chevrolets used only an o-ring seal mounted on the valve stem in conjunction with an oil shield mounted on top of the spring below the valve retainer as a means of keeping oil away from the valve guide. The o-ring seals break down in time and become ineffective. With an engine like your 72 LT-1 which has drippers inside the valve covers, extra oil can "cascade" through the valve retainer and onto the upper valve guide where induction system vacuum causes it to be drawn into the combustion chamber. The fix to this problem is to replace the valve seals which can be done with the heads installed on the engine. It will require about 4 hours of shop time, so you can use that to estimate cost since most of the expense will be labor. Also, I recommend that in addition to replacing the o-ring seals on all of the valves(intake and exhaust) that Viton rubber positive seals be used on the intake side. These are the seals that GM started using in 1981 on small block intake valves. They are GM #460483 and GM list for $3.05/ea. They can also be purchased easily through aftermarket channels. Just ask for VITON, positive-type valve seals for a Chevrolet small block.

All of the above assumes that your engine has IN REALITY only 27,000 miles on it. If it has 127,000 miles, you will need much more than valve seals. Generally, with this mileage the valve guides and/or valve stems will be worn. This greatly affects the ability of the seals, even in perfect condition, to seal the combustion chamber from intake valve oil contamination. In fact, if the valve guides and/or valve stems are worn, it's a total waste of time, effort, and money to replace the valve seals, alone. In that case, you will need to remove the heads and have them completely serviced, assuming that you don't need additional bottom end work.

Another problem which can cause induction-induced oil contamination of the combustion chambers is a leaking intake manifold gasket. This is a little-understood problem which plagues small block Chevrolets. It is caused by oil mist being drawn out of the lifter valley, past the bottom edge of the intake manifold gasket and into the intake ports. Usually, oil-wet intake ports observed upon removal of the manifold are a tell-tale sign of this problem. Sometimes, it may require machining of the intake manifold to correct it and obtain a good gasket seal. Other times, simply replacing the intake manifold gaskets can resolve it. Never use the rubber or cork end gaskets found in intake manifold gasket kits. Instead, use Permatex "Ultra Black" or "Ultra Copper" high temperature, oil resistent silicone to carefully seal the intake manifold-to-block end seal areas.

[STEVE MUELLER]

Re: 1972 LT-1 OIL SEAL PROBLEM/ENG DIAGRHAM

Mr Lucia:

I thank you for your response. please let me go into more detail on whats happen with the motor. First, the car really does have only have 27,000 miles, there is no doubt on that. Second, when I looked at the car a few weeks ago it did not smoke, when I had the car transported home and I ran it in the driveway I noticed two items

1. It was running very rich( IE it was burning my eyes)

2. It started puffing a semi blue smoke.

Also I took the car up and down the block and ran very well. It had an extreme amount of power. I can for the life of me understand what happen?

[Joe L.]

Re: 1972 LT-1 OIL SEAL PROBLEM/ENG DIAGRHAM

Steve-----

The rich running condition can really only be a symptom of a carburetor problem. The car may have the float level set too high, have a failed power valve, or have some other problem. If the car previously sat for a long time without being run, some of the gaskets in the carburetor may have dried out.

As far as the blue smoke goes, you could easily have the valve seal problem which I previously described without suffering from any loss of power or engine performance. Valve seal problems usually don't, by themselves, result in any significant performance deficiency.

[Dave]

Re: 1972 LT-1 OIL SEAL PROBLEM, need more info

Here's a thought your oil question: Did you change the oil when you got the car? If the car had 30, 40, or 50 weight oil in it when you tested it prior to purchase, and 5w30 was installed after you bought it, you would have the problem described. As for rich carb, is the car at the same altitude (above sea level) as it was? Is the air filter clean?