Worn Valve guides

[Nima]

Hi everybody:
I just read a thread about using vacuum gauge to ajust a carb. One of the thing which was mentioned was " if the needle vibrates heavily at idle but become steadier as rpm goes up, is indication of Valve guide problems".
Well, being a newbie here, other day I was playing with my carb and new vacuum gauge trying to set the carb at it's best, then I noticed that when the vacuum gauge is connected to full vacuum, at idle it vibrates between 15 and 20, very fast. Is there any other sign(s) for valve guide failure or the above test is written on stone? If it is vavle guid problem, how can I fix it? Thanks.

[JimKshortstep4x4]

You may want to check out the guides to determine if they are bad or not. I would do an adjustment on the valves first. If that does not cure it then if you have the equipment, pull a spring and check the looseness of the valve in the guide.

If your guides are worn then pulling the heads and installing new guides is the way to repair them. (You can also purchase new or rebuilt heads.

[Nima]

Thanks for the reply.
If the problem is the guide, what will happen if I let it go for now? Would it damage anything else? This truck is weekend driver at this point. Thanks again

[JimKshortstep4x4]

A lot depends on how bad the guides are. In general you should have some time before anything serious happens.

I had another thought on your problem that I wanted to pass along. A worn camshaft can do the same thing, so you may want to pull the valve covers and watch the rockers go up and down. With a worn cam the rocker(s) will not move much.

Jim

[Nima]

Thanks Jim. Now another thing came to my mind. If it is valve guid or cam shaft, how can I find out which side it is? or I just have to pull both valve covers out and see?

[JimKshortstep4x4]

A compression check will give an indication, but it is probably easier to pull both covers.

Jim