Broken Intake Valve
 

Anybody ever seen anything like this?
http://img245.imageshack.us/img245/184/dscn1621.jpg
http://img245.imageshack.us/img245/1794/dscn1619j.jpg

Are those areas burned?

Remove the valve and look at the seat.

It looks like little pieces were breaking off, not burning. I'll be tearing the heads down later this week and updating with seat pics if I find anything.

Try to see who makes that valve, I have seen pitting on valves from water on mostly the stem side, thats really strange! Looks like the valve rotates to one spot then begins to remove material, I take it the engine would back-fire through the intake.

As far as I know, the valves are factory but I'll check today. The engine actually ran fine with no backfire. I'm tearing it down due to a bit of oil consumption and found this by surprise.

Are you the original owner of the boat?

Are all the valves this way, or just a few?


There is a lot on info out there that would help, like what kind of engine is this? How, old, how many hours, salt/fresh water?

It might be just me also, but it looks a little lean hot in that chamber also. Are these factory engines?

What I find unusual with this, is that the intake valve appears to have gotten hot, not the exhaust??? Weird.

It is only one valve that has done this. The engine is a 9.0:1 454 with fact rectangles (088's). The valve are original from merc and have approx 100 hours on a valve job. I don't know the total number of hours. The cam is stock with 1.8 rockers and the exhaust is stock as well. It is used in fresh water only. The engine was tuned with a LM-1 and ran approx 12.5:1 at wot.

13.6 is leaner than 12.5.

Looks lean

Running that rich and n/a your cylinders should be black. Yet the chamber looks steam cleaned with no carbon, unless that is just the pic. How does the piston top and edges look?

Here's a pic of the piston from that cylinder.
http://img218.imageshack.us/img218/4163/dscn1622e.jpg

tj,

That is what you call a "burnt" valve. If it only is the one valve and it has 100 hrs since a valve job, I would bet that either water has been getting into that cylinder, or the valve job was not done properly, causing the valve not to seat properly in the places where it is burnt. Without having the head or valve to look at, its hard to speculate about the cause.

Bill Koustenis
Advanced Automotive Machine
Waldor fMd

I'am still wanting to see what he says about the valve seat, I told him that the valve looked like the valve was burnt in those areas shown, I would be willing to bet the seat is bad or the valve job is bad.

You also said 1:8 rockers. With that rocker the cam might not be letting the valve close all the way once the engine gets hot. You could have had it a little to tight giving the impresion of a bad valve seat. When valves do not close all the way, the heat from the valve can't dissipate into the seat. If it is not closing all the way, eventually during combustion, it could burn away part of the valve by allowing heat to pass by the valve.

But it still looks way to lean, or the timing is to far advanced. The rockersize increase can cause all of the above if not careful.

I am planning on tearing the heads down tonight and getting more pictures. If anyone would like to see larger pics of the valve, send me your email and I'll send them to you. With a larger pic, the missing pieces look to have broken off, not burned/melted. Also, you can see a crack coming off one of the broken areas. Thanks for all the help so far.

looks like heat got them to me...Rob

They are burnt, take my word for it.

Also, pictures might not show anything. You need to have a good machine shop check the valve job for concentricity and proper contact width.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Hey Bill, look at the valve relief, I just noticed that it looks burnt away also.

Are you thinking pre detonation?

I don't know at this point, Since I don't have this thing in front of me Jeff, it's like calling the Doc. up and telling him your sick and thats it and you want some meds. The guy didn't even notice the burned out valve relief.

Here's another pic of the same pistons I'm running. I found this on the web, it is not a picture of my piston.
http://img110.imageshack.us/img110/2776/pis.jpg
Here's a couple of the seat. My camera isn't very good, so these might not be helpful.
http://img220.imageshack.us/img220/631/dscn1628.jpg
http://img220.imageshack.us/img220/3355/dscn1624.jpg
With the valve out and cleaned up, you can see small cracks all around the outside diameter. I had forgotten about it until now, but the engine did consume enough water mist to cause a noticable misfire my first time out last year. Maybe this problem was brewing all of last year, and I just got lucky finding it before serious damage occurred.

P.S. I've compared the heads in person to the pictures. The pictures definitely make everything lighter (leaner looking) due to the flash I presume.

I didn't even look at the piston picture. Kind of hard to tell for sure, it might be machined that way ? I think the head needs to go to a good machine shop to be examined properly, hard to tell much from pictures without doing some measuring. Same goes with the piston .... if all of them are like that it probably is not an issue, but if that is the only one it needs to come out :(

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

I have an engine with those pistons in it.

Have you looked up the comp ration with the part number on the piston.

That piston does have the side of the piston machined off the side of it, but it is a very brittle part of the piston. When the pistons break, that is where they break.

The cause of the breaks are usually detonation from the wrong timing adjustment, or a leaky exhaust mainfold or header.

But backk to the original question of the valve, I think it goes back to the 1.8 rockers.

Did this engine come stock this way???

MER, what do you think about my rocker theory?

All of the pistons are like that. I wouldn't have missed a burned valve relief. The heads will be going to machine shop eventually, I just wanted to get some opinions here. Thanks again.