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.