I am cleaning a set of L31 Vortec's that were on a 350 for 3.5 months and two things are strange to me.

1. The combustion chambers, pistons and intake valves have alot of oily build up on them already even on the intake side of the valves.

2. After pulling the springs to inspect and clean the valves I noticed alot of play in the valves and after checking side movement with a dial indicator there is about .004 on them all.

This amount seems like too much in both the build up and in the amount of valve stem clearance.

Thot's?

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91 RS 5.0 TBI....LT4 cam....Edelbrock headers....3"Dynomax exhaust....5spd.... 3.08.....Ultimate tbi....afpr...ZR 255-50's...Koni's

 

sounds like they could use a rebuild, its not really all that expensive.

 

My main question is what made them wear that fast? Only 3 months.

What type of quides should they be replaced with?

 

could have just been done poorly, make sure its the guides that actually are shot, if you saw smoke on start up or slowing down when driving, then its forsure the guides. or could be a head gasket if not those problems.

 

The story is the heads were new in June when I installed them on a 350 which 3 months later deceided to eat a TBI pod bolt. I have removed the heads and have them on the bench. I noticed that the pistons were very dirty for such a short time running and then looked down the intake ports on the heads and noticed buildup on the back of the valves.

After removing the springs to lower the valves to clean them I then noticed the play in them and checked them to have .004 side movement. WTF These were new..

 

Oh yeah I forgot; no smoke or anything. I did not know of a problem until teardown.

 

were they loaded with just carbon or oil? if there was no smoke i dont think its the heads, just sounds like it was running really rich loading up everything.

 

I would guess carbon. Not oily like checking the dipstick but dark and grimy.

You might be correct about the tuning. It ran good but I never had gotten into tuning the cruise and idle modes that much.

What are the spec's for valve stem clearance? The stem's themselves are within tol of the spec's that I can find for them.

Thanks for the help!

 

I cant remember what the spec is supposed to be, but that sounds high. I'm thinking its supposed to be like .002 not 4
Excessive wear is generally caused by lack of oiling or poor valvetrain alignment. There are other causes, but those are the major ones. Might wanna pull a valve and see if its the same diameter everywhere on the stem.

 

I've pulled two intake's and they mic around .3405.

Am I checking the play correctly? I mount the dial indicator as close to the guide as I can and then lift the valve off its seat, push the valve to one side, set o and then check to the opposite direction.

 

you can tell bad guides, just look in the exhaust port at the valves, if there leaking you'll see the lines of oil leaking down, sounds be me like the heads are fine, and you said you never tuned it so i bet it was just running really rich and carboned everything up.

 

You could be correct. I'll finish cleaning them and see how they do. I know that the engine that they are going on now has a much better tune than the 350 did.

Thanks for all the help!