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  #1  
Old 11-13-2002, 11:28 PM
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Default Sticking Valves

I have a 392 in my truck and it seems to run just fine at an idle or any throttle speed until it starts to warm up. Then on occasion one of the intake valves will start to stick and cause a really loud popping out of the carb resulting in horrible drivability. You cannot hardly touch the gas and it will sputter and pop bad. But if you can manage to get going down a hill and let off the gas generally it will stop popping and run normally.

My question is, is there any way to cure a stuck valve without rebuilding the heads? That is a way I would prefer not to go. Is there any other way possible?
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  #2  
Old 11-18-2002, 02:20 PM
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Default Re: Sticking Valves

Are you sure the valve is sticking, and it's not something else?

When my valves would stick, I would always break a rocker arm and a pushrod in the process.

This only happens when warm.. how about an EGR problem (sucking air?) or timing being off or...
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Old 11-18-2002, 04:30 PM
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Default Re: Sticking Valves

The Timing is correct, and it doesn't have EGR. I really can't think of any other thing other than a sticking valve.
This is what happens. How would the EGR do it? I have a plug in my exaust manifold that might have been hooked up at one point but is not any more. Where would the spot be on the intake manifold for the EGR? Maybe that is leaking if it is plugged but it is not hooked up or there on my engine. The owner before me wasn't too bright so he might have disconnected it.

When it does pop, there IS an explosion in the intake manifold stopping airflow to the engine untill it has burnt it all up then on the next intake stroke it will fire and run again. This is only when you are really on the throttle trying to accelerate. As to breaking pushrods that is what I was doing until I bought new ones (had old ones laying around that were straight at least).

Also now I seem to have another problem. It smokes horribly out of the drivers side exaust. I have no idea why, I have been told that it is probably a stuck ring or somthing like that but what is weird is that before it has smoked for a while then it magically stopped for a while. Now it is smoking again, I am guessing it will stop after a while again but it gets annoying driving with a smoke screen. Any guesses?
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Old 11-18-2002, 04:46 PM
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Default Re: Sticking Valves

</font><blockquote><font class="small">In reply to:</font><hr />
The Timing is correct, and it doesn't have EGR.


[/ QUOTE ]

What is "correct"? There is no "correct".. just what works, and what doesn't.

One engine may want 15deg BTDC, another won't run at more than 2BTDC..

</font><blockquote><font class="small">In reply to:</font><hr />
How would the EGR do it?


[/ QUOTE ]

I was thinking the EGR opens under certain conditions. I believe one of those is controlled via a vac. temp switch.. so it only works when the vehicle is warmed up - and you indicated the problem only happens when it's warm.

</font><blockquote><font class="small">In reply to:</font><hr />
Where would the spot be on the intake manifold for the EGR? Maybe that is leaking if it is plugged but it is not hooked up or there on my engine. The owner before me wasn't too bright so he might have disconnected it.


[/ QUOTE ]

EGR is at the center/rear of the intake, behind the carb.

Round pancake type device, with a vac. line hooked to it.

IIRC, it's supposed to work such that when the vehicle is warmed up, the vac. will pull on the EGR and cause it to open, which lets exhaust gas go into the intake for more complete combustion.

That may not be the problem though.. as I think on it, more likely.. say the EGR was disconnected, but the vac. line to it was not plugged off (or someone shoved a bolt in the rotten hose, etc).

Now you have a plain old vacuum leak - but since it goes through the temp switches, you only have a vacuum leak when the engine has warmed up. When cold, those switches are closed and the leak is plugged.


</font><blockquote><font class="small">In reply to:</font><hr />
When it does pop, there IS an explosion in the intake manifold stopping airflow to the engine untill it has burnt it all up then on the next intake stroke it will fire and run again. This is only when you are really on the throttle trying to accelerate.


[/ QUOTE ]

If it's a vac. leak it could be running lean when the vacuum leak opens up. That could cause it to ping, and may lead to backfiring.


</font><blockquote><font class="small">In reply to:</font><hr />
Also now I seem to have another problem. It smokes horribly out of the drivers side exaust. I have no idea why, I have been told that it is probably a stuck ring or somthing like that but what is weird is that before it has smoked for a while then it magically stopped for a while. Now it is smoking again, I am guessing it will stop after a while again but it gets annoying driving with a smoke screen. Any guesses?

[/ QUOTE ]

Smoke non-stop? Smoke when under load? When compression braking? White, or blue smoke?

Compression braking blue smoke may indicate a shot valve guide.

Smoke all the time would be worn rings, while I think under-load blue smoke may indicate the same, but to a lesser extend.

White smoke is a head gasket leak. Fix it sooner than later (bearings don't take kindly to antifreeze mixed with the oil).


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  #5  
Old 11-19-2002, 12:15 AM
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Default Re: Sticking Valves

It doesn't seem to ping when driving or under load. The best part about the smoke is it looks white, but smells of oil, and (at least it has) fixed itself on its own without anything from me. There is no water in the oil either I have checked it regularly and this is the first time the oil level has dropped. I will play with the timing idea tomorrow. I will do a compression test and maybe a cylinder leak down test if I turn up an odd compression reading on a cylinder. Thanks for the idea's, I really appreciate your help.
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