How do you know if your valve guides are leaking?
I did a comp test on my car everyone was 175-180.
The car had been starting and driving fine. Last week when I was leaving work I started the car up and a cloud of smoke billowed from the exhausts only lasted 15 seconds then went away. If I leave the car for an hour or more the same thing will happen smoke then nothing.
If the guides are leaking is this a relativly simple fix? or costly?

Sounds like the valve seals are leaking, allowing oil to run down the valves and dripping onto the piston.
If the smoke clears up after a few moments, thats usually the problem. If it was piston rings, it would smoke constantly.

The valve seals control excessive amounts oil from running down the guide. You may have had a seal come loose or go bad.
Sarge

Sarge81 said: Sounds like the valve seals are leaking, allowing oil to run down the valves and dripping onto the piston. If the smoke clears up after a few moments, thats usually the problem. If it was piston rings, it would smoke constantly. The valve seals control excessive amounts oil from running down the guide. You may have had a seal come loose or go bad. Sarge

i concur probably a stem seal.. are you getting smoke from one side or both... can you isolate which cylinder is getting fouled..

I dont know what kind of seals you have in that beast

there are three kinds i know of... maybe the master knows more..

umbrella, flat o-ring, regular o-ring..

i dont remember off hand but umbrella are used with one of the o-ring types...

also there is a way to vaccum test this for leaks... you need some kind of hood... i dont have one.. never done it..

the condition you are describing is almost always a valve seal.. you had a good comression test and this tells me there isnt much lateral movement of your valves and therefore the guides are probably good.

to replace your seals you will have to pull the vavle stem keepers.. (which means replace them... never re-use)

this can be done with the heads on the car... one way to do this is to hook up an air compressor to the plug hole.. this will let you take the valve keeper off without the vavle dropping... the other method involves jamming something into the plug hole... cant remember what though...this also keeps the valve from dropping.

there is a tool to compress the springs using the rocker stud as a pivot.. I dont have one and dont know where to get one.. i usually use a block of wood.. use a spade bit to drill out a hole to go over the spring then cut a slot in it that allows me to get to the keepers..

i personally think it is easier to do this with the head off.. I would probably take this out to a machien shop to do... but in the past when i was more adventurous.. i used a valve springs compressor and did it by hand..

if you are a glutton for punishment and want to do it yourself, ive got a valve spring compressor ill loan you... ( i havent used it in five years.. and hopefully i never will again)

Had the valve stem seals replaced a few months ago. I was going to do it myself but got cold feet. It's about a four hour job if you know what you are doing. The cost was $350.00. Had to change the spark plugs too as they were fouled with oil.


Roy

Thanks everyone, I will keep you posted as to the outcome

Sorry I haven't been on for a couple of days. Busy.

Everyone is on target. The valve stem seals are leaking.

The original valve seals are an o-ring type that don't seal anything. They actually just splash the oil off the valve stem before it runs down the guide. But they do wear out and give your exact symptoms.

Ben's method of replacing the seals is accurate. I have done it many times.

But you can use a different seal and avoid a lot of work and time. They work just as well, if not better. I always gave my customers the choice.
It's an umbrella type seal. It just fits on top of the valve spring, and seals around the top of the valve stem. They work very well. No oil down the stem. The rocker actually holds it in place.
All you do is loosen the rocker, insert the seal, and adjust the rocker back to where it was. Done.

Several different GMs used these as factory seals. I will have to go back and recheck the application. It's been a few years from the last set I installed. I used to have the listing in my tool box. I have used them on many GM, Ford, and Chrysler engines with excellent results. Smaller valve stems in many newer cars won't seal and won't work. They are great in most all American V8s and older style V6 engines.

I will do some checking and find the seal application for you.

i looked it up and the umbrella seals are used in conjunction with the flat o-ring seal..

id go ahead and replace the o-rings and put umbrellas on.

while your at it ken... think you could find ones to fit an l-36... ill be putting on comp cams mag pro rockers when i get back from germany... id like to put umbrellas on too..

i just replaced my o-rings when i did my head work last month.. but couldnt find any (but I was in a hurry)

My 79 called for o-rings.I used both umbrellas and O-rings by "Perfect Circle."

Smallblock said: My 79 called for o-rings.I used both umbrellas and O-rings by "Perfect Circle."

got a link for them ?

Sorry no link. The Perfect Circle seals are hard to find.Just looked up parts supply in the yellow pages and started calling until I found them.