Hot Boat

I just took off my head and the # 8 intake valve is bent. If the valve is standing straight up the stem points to 1 o'clock. I believe that I might of had reversion but I don't know for sure. There was small water droplets on the spark plug when I pulled it immediately after this disaster happened. I only ran the motor for 1 hour when this happened.

It happened when I was at a fast cruse I first heard what sounded like the blower belt slip for a split second. I backed off the throttles and the boat seemed to be running fine for about a minute. I went to accelerate and a few seconds later I lost a cylinder. . Oil temp was 220, water was 100, water pressure was 25 psi at WOT, boost was 5 psi. oil pressure was 60 psi. , everything felt fine up till I lost the #8 cylinder pressure. and even after that I still had all good pressure and no knocks or odd noises other than the loss of compression on that cylinder. .

I noticed that the valve lightly hit the piston . there is a slight mark on it where it hit but I don't think this will affect anything.

what I am curious about is why did the valve hit????

Is it possible that the valve got stuck open under reversion and thats why it hit ???

Also...... Around the dock the motor hunted alot and the idle would drop down to 500 rpms and it stalled a few times. I would geus that this is when the reversion would of happened. If that is when the reversion happened . is it possible for valve to break a few minuets later?????


Why, Why , Why Me Again.

bobby daniels

I don't think that it happened around the dock
It might have bound in the guide this happens like you discrided
or detonation can keep it open and hit the valve either way above .be sure to check the heads very well ,
I have a 35 fountain in the shop now that has prochargers an it has the same problem on cyl 1 ,wild

also cold water hitting the valve could have bent it and let it hit the piston ,head gasket ,detonation ,old gas ??
Pm me if I can help

Hot Boat

Thanks bobby

The motor was just dyno.(sp) and only ran for 1 hour after words. While on the dyno They ran the motor at 5000 rpm for a few minuets under a load to watch the EGT's and it was dead on the money. It had fresh sunoco ultra 94, I don't think I had a lean condition . all the plugs look good and there is a ton of black carbon on the back of the transom.

I am almost positive that I had a leak in one of the runners in my headers, so reversion would of been inevitable. they were old lightning headers that were all steel. not stainless.


I just went and bought a set of gill manifolds with long risers. They should solve my reversion problem.

Hot Boat

I checked the head and it has a cracked guide . I assume that it happened when the valve bent, But I really don't know????

bobby daniels

Knowing this your most likly right as the cold water will bend and
warp valves then they stay open until the piston slaps it closed ,,,sorry if I can help I will
ITsounds like it was done right ,good luck

bobby daniels

your right broke when it bent ,,,but check the rest and guide clearances

Hot Boat

Hypothetically .. If I didn't have a leak in the headers and I had a cracked guide . is the guide in the water jacket ??? and is that where the water came from???????

WETTE VETTE

I would find it strange that the intake valve would be affected by reversion. I would guess the intake valve would be much cooler than the exhaust. Doe the valve show any signs of becoming tulip shaped? I have seen detonation/pre-ignition cause intakes to start to tulip and I am sure the valve could ring and not shut all the way or something if it is severe enough. I have had reversion problems on motors, but haven't had valve problems because of it. Could there be enough water entering the cyl that a hydraulic lock could be starting to take place? If so how are the rods doing? Just throwing ideas. Good luck and let us know.

Hot Boat

Thanks WV

From what I was told is that the intake valve are more subseptable to reversion becuse thay are not as strong as the inconal exhaust valves.

WETTE VETTE

That makes sense. I am a NA motor guy so I forget you huffer guys run inconels on the exhausts. If water is getting in the comb chamber at idle could it cause the lubricity on the valve stem / guide to be substandard? If so there may be some galling on the valve that would indicate the valve hanging up a bit. Let us know what you come up with.