Funky Exhaust Valve?

JustABuick

Active Member
Joined
Feb 13, 2013
Hey everyone,

My car was getting a flutter on hard acceleration above 20psi (kind of sounded like a piece of paper flapping rapidly). I figured it was probably a lifted head or a busted gasket, so I pulled the engine, got the heads off, and the gaskets looked fine. Checked the cam and lifters, and they looked fine too. A friend of mine came to check it over who has been working on these cars since they were new, and we noticed on one of the heads (Can't remember if it was passenger or driver's side, i'll have to double check) the middle exhaust valve stuck up just a little bit higher than the others using a straight edge. They are iron Champion heads with larger valves (probably ones that come with Champion heads...they were on the engine already when I bought it).

I don't know what else would be causing the issue, new plugs, coil pack, and wires were used before the engine was pulled, none of those fixed it.

Could it be the valve? Would an uncut or stretched valve cause that issue? Should I get new valves or just get a machine shop to cut that one down, mill the heads, and reassemble it?

Thanks,

Kelly
 
I would definitely pull the valves and possibility replace/measure them. It sounds like your valves are starting to "tulip" which means the valve itself is becoming more and more dished on the head. Causing the stem to protrude further through the guide, resulting in way incorrect spring seat pressures and compromised valve sealing. From the sounds of your symptoms that one valve was starting to float because of it.
 
Okay so it definitely sounds like it could have been the issue. What's the recommended place to get new valves? If it wasn't detonation, I can leave the surface of the heads alone, right?
 
It never hurts to check the surface with a straight edge and a feeler gauge. I am not sure of your abilitys but when it comes to replacing valves you need to check spring seat pressures, verify the guide and cut the seat. You might want to take it to a machine shop.
 
Ive seen exhaust seats deteriorate as well, it will cause the same issue. It either needs a new valve/valves or an exhaust seat replaced.
 
I'll check the surfaces, but I'd feel more comfortable with a machine shop doing it. That is probably beyond my abilities right now. Okay, i'm hoping this will fix the issue. I just need to find a place that can do it soonish.
 
When using valve springs with a lot of seat pressure it is common for the valve seats to recede in the heads.
 
Many years ago I was an engine machinest. We did alot of industrial engines, 366 BBC's were bad about it. Mostly because the drivers would leave their foot on the floor with a heavy load all the time. The constant exhaust temps just ruined the seats and valves.
 
Yeah, Rob may be correct in that they were just not cut to begin with? I assume it will be evident when I pull the valve. Probably most any competent machine shop should be able to handle it, right?
 
So I took the heads to an engine builder/machine shop today and they wanted the specs on the cam to verify spring install height. I'm running the Champion irons, T&D 1.55 roller rockers, Comp 980 springs, and a Reed 210/205 flat tappet. So far, a friend helped me track down this info on the cam.

Duration @ 0.050 tappet lift - Intake 210 deg - Exhaust 205 deg
Valve lift with 1.6 rockers - Intake .470" - Exhaust .459"
Lobe Centers 110 deg
Recommended seat pressure 80-100 lbs.
Recommended open pressure 260-280 lbs.

Should that info be sufficient, or does anyone know the spring install height, and I can take out all the guess work for them?
 
I forgot to take good pictures :( I might have a couple of crappy ones from earlier, but they probably won't show anything. I can take some when I get the heads back, but the point will probably be moot.
 
You need to pull the valve and see if the exhaust seat is pounded in or if the valve face is eroded away.

Any halfway competent machine shop should be able to visually look at the seat and/or valve and tell you if it's shot within milliseconds.

Spring installed height is 1.727" but it should be set based on poundage not an arbitrary height. The tip height is what you noticed when one was sticking up higher than the rest and I don't recall what that spec is off the top of my head (the AERA book is at the machine shop :) )
 
High probability there was an ignition problem


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You need to pull the valve and see if the exhaust seat is pounded in or if the valve face is eroded away.

Any halfway competent machine shop should be able to visually look at the seat and/or valve and tell you if it's shot within milliseconds.

Spring installed height is 1.727" but it should be set based on poundage not an arbitrary height. The tip height is what you noticed when one was sticking up higher than the rest and I don't recall what that spec is off the top of my head (the AERA book is at the machine shop :) )

Thanks Earl. The machine shop said the heads looked good, there were no cracks, and the seats were in good shape. They are going to do a valve job, resurface the heads, and there are a couple of broken dampers.

They asked for lift, and referenced some book/chart for install height, I assume that's the same one.

High probability there was an ignition problem


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Like "need new plug wires" issue, or something more serious?
 
Springs are cheap. I'd replace them if you've already lost some dampeners.

Stick a new set of rocker buttons in there too.
 
I'll definitely have them throw new springs in. Sounds good. I'm surprised there wasn't any damage if the valve was tuliped.
 
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