Broken Valve
 

I have a early 90's 454/425hp motor that broke the # 6 intake valve. Took the boat out to the lake and unloaded and idled out of the no wake zone. Everything was good, got the boat up on plane and made it about 1/8 of a mile an heard a loud pop and the motor started missing. Was running about 3000rpm, hadn't even opened it up yet. I shut it down and did a once over on the water and didn't see anything obvious. Idled back to the ramp and loaded it up. Got it home and started the basic troubleshooting, found # 6 had no compression. Remove valve cover and everything was ok, pulled the intake and handed to by buddy and he noticed something rattling around in it, he moved it around and guess what fell out? part of a valve fell out. Never seen that before. Anyway remove the head and part of the intake valve was broken. Top of the piston looked good, not hit marks, but from about 7 oclock to 11 oclock the cylinder looks like it has been hot and scored. looks like I had two problems, looks like the valve was bad, but not sure how to explain the damage cylinder, wasn't lean or detonation. Any thoughts would be appreciated.

Do any of the other valves look like they are tulip'ing?

Not that I can tell. Thanks for the reply

KS,
That valve has either been very hot like you mentioned, or water was getting into that cylinder which will also tulip valves like that. I would bet more on the heat though. You say it wasn't lean, how do you know ??? How about a picture of the top of the piston and the one in the cylinder next to it ?

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

to much timing, lean, or water...buy a lottery ticket that the whole engine is not door stop material...

Check the other side.

Billk:I will get some pictures tonight of the other cylinders. The reason I dont think it was lean is all visual, it actually looks fat to me. Everything looks rich, plugs, pistons, exhaust, ect. I could be wrong. I have CMI's on this motor and did just pressure check them a month ago. Would I see any other signs if it was water? Thanks for the reply

Ezstriper, timing was total timing of 30 degrees. It sure didn't look lean, but I could be wrong. I'm wondering about the water since I have CMI's. Thanks for the reply.

Reds32,

I haven't checked the other side yet! Still depressed from the other side! lol!

Water will give a steam cleaned appearance to the piston top and chamber. Yours looks mighty clean in my observation.

Blue Thunder, The motor has about 140 or so hours on it. So you think I have a water issue? I pressure checked the CMI's. They have the silent choice divertors. Do you think I could be getting some reversion? This is a factory built motor and I believe the cam is a Crane # 132561 duration is 228/235 at .050 with 530/551 lift. If it was water woudnt the exhaust valve be the one broke or does it not matter? Sorry for all the qustions. Thank you

Don't try and be lucky twice in a row!
 

Intake valves do not really run hot or lean in an engine like this and the water from exhaust if coming in, comes in on the exhaust valve , not the intake and seat rusting and such is usually very visable.
My guess is just either an old tired set of valves or valves of very poor material that just caused the valve to crack and fail. My suggestion is to get all those valves out of the engine and install a nice new set of stainless EV8 intake and exhaust valves, Manley, Rev, Howards, etc. make some good sets for reasonable dollars.
Don't take the chance of another valve failure, you were really lucky you did not loose the whole cylinder or even block!!

Best Regards,
Ray @ Raylar

The pics do look steam cleaned to me. The reason you need to replace all the valves (severe duty manley on intake, faria inconnel on exhaust would be my preference) is because the better valves can take a bit of water spray from slight reversion and not get brittle. Plus the other rigors of marine engines (high heat particularly in the valve train) require the tougher valve. Raylar is right on with his advice as always. You really need to do all the valves and also make sure the springs are fresh. Pounding on the seat from the lifter coming off the cam can cause this too. The valve is cooled while on the seat. Weak springs result in less seat time for the valves.

Did any of the other cylinders look like this? Check to make sure you did not have a head gasket leaking water into the cylinder. That could explain the broken valve and the score marks if it was washing the oil off the walls. If it had ingested something you would see signs of it on the top of the piston, and it looks like you have the entire piece that broke off the valve.