Noise Pollution

I've stuck an exhaust valve for the second time. It's more than a clearance issue. The valve stem had plenty of clearance in the guide when it was assembled. For some reason it seems like the guide shrinks and the valve sticks. It has always happen when the oil is not up to temp. Dart Heads with Mag/bonze guides. The last time , the guide had a dark color inside the guide. You would think it would be shinny from the valve stem. The guides were honed to size instead of using a reamer. Can't see where that should make any difference.
Water temp runs 150*
Anyone run into this??????

blue thunder

How do you know the valve stuck, what were the symptoms? It seemed to be running good yesterday, was there deterioration in performance after the sticking event?

Anyway, things that come to mind for me are clearance, valve train geometry (side loading valve) , running lean combined with running too hard before the oil is warmed, broken inner spring or wrong open spring pressure, broken push rod guide, bent valve stem, reversion causing some corrosion on exposed stems during non run times.

t500hps

Oh chit....I was thinking about you just a couple days ago, guess this post tells me how things have been going. Good Luck.

Russ C.

Biggus

iTrader: (1)

I had a similar problem years ago.
After sticking an exhaust valve (same cyl) over and over, tried different guide materials, clearances etc. we finally found the cause after a complete tear down... there was a chunk of rubber impeller that made its way into the block and water restricted flow to the head.

Noise Pollution

Dave, At first its just a hipcup when I first get on plane. Then it start to happen more and more. The valve doesn't totaly stick open at first, its just slow closing. When the valve starts to stick you feel the lose of performance big time. Every thing you mention has been look at. I have 02 sensor in the exhaust , so I know the air/fuel is fine. Matter of fact at idle its rich, around, 10. The only thing I can think of if my egt's are high. Usually in a car when someone sticks a valve its because they got the motor hot. So thats out in this case. Last time it happen I thought about leaving the seals off the exhaust valves, but shouldn't have to do that. I guess I get it figured out.

Noise Pollution

I've had the same problem on both heads. I've thought about the heads getting hot. Doesn't seem like it though.

Noise Pollution

Any engine builders out there? Ideas??

blue thunder

How about wrong or upside down head gaskets Mike? Is it always the same 2 exhaust valves? One one each side.

Noise Pollution

Cometic head gaskets. The bolt hoes will only line up one way. Last two times was #5 cyl.

BillK

Noise,
Actually, engine coolant temperature is usually not the problem. The problem is with combustion chamber temperature. If the one cylinder is a little lean, or the timing is retarded, etc and the valve itself, not water temp, is too hot, the valve actually expands and sticks in the guide. You mentioned that your EGT was high .... this is probably a clue to the real cause. A blocked water passage to the area involved might make it worse, but I bet if you track down your egt problem, you will stop sticking valves.

Also, what is the actual guide clearance you are running ? Honing the guides is the preferred method of sizing.

Hope this helps,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md