What happened
 

Only 12.6 hours on the clock. Builders is standing behind his work and going to fix it. Just looking for some of the engine builders opinions. Most of the hours are cruising 3500rpm of course a few wot passes 5400rpm MSD ignition and soft touch limiter with a 5800 plug.


http://i927.photobucket.com/albums/a...G_00000999.jpg.

Last fall different cylinder http://www.offshoreonly.com/forums/g...?highlight=598.

Looks like valve stuck open and got whacked. Thats pretty ugly stuff there .

Another valve guide clearance thread in the making?

jeepers bro .. dam youre luck ..i feel for ya .. :(((((

Ouch! Were the heads new assembled units? If so it my have had a tight guide and the valve seized. Props to your builder for standing behind his work. In the time we live in it seems we hear more horror stories than good reputable people. Hope it all works out.

looks a little lean compared to the other cylinders.to much heat will stick that valve..could also come down to water flow thru the cylinder head.2 engines down,,something in the set up is amiss.

He used the block head castings crank and rods everything else was new.

Just trying to answer questions and educate my self. So I appreciate all responses.
Water temp barely over 100 oil temp 185 to 190.
Different cylinder than the first time opposite side this time.

Yes it sucks. But I know there are others with alot worse problems than a damaged boat motor. So I'm a lucky man.

Does that exhaust port look steam cleaned or is it just the light.

Just the flash. No water leaks

this happened twice? looks like a good case of OOPS NOT INCONEL... to me.....

12.5 hours mainly cruise time in an n/a motor they could have been ss and should've lived through that

Build sheet says inconel and I insisted on inconel.

hmmm that's odd, would have had to stick in guide then I would think, Inconel don't break unless that happens, I had one so hot it started to tulip so bad it cracked, still didn't break off...

However, more people have f*ked up A/F ratio issues at cruise than they do idle and WOT. Many meltdowns happen while 'cruising.'

Good point,

Do you run a cross over? IMO 100* of water temp is not enough. I also think you should have water lines from the front to back on the intake manifold.

I run crossovers no stats, no water line to back, never been issue, been that way 10 years...

loose clearances are a MUST in that case though...

Yep! When I had my engine run on the dyno I asked them to put a load on it and run it with a steady state test from 3500 RPM to 4500 RPM. I wanted to make sure we had good A/F numbers in that range, and also wanted to ensure that there would be no oil drainback issues with valley screens installed. While running this way, we saw it go pretty lean and the headers began to glow. If I had simply dropped it in the boat and run it after making several quick pulls on the dyno for WOT power data, I am 100% sure I would have likely melted it down at a fast 4200 RPM cruise.

Yes crossover no stat ran it 3 season that way before the first failure and the previous owner ran it the same way.
Shortly after I got it I installed a restrictor because it had no engine temp when running.
The builder was aware of the water temp and oil temp beforehand started the first rebuild and was comfortable with them.

Good info. This was not done when it was dynoed. I will ask it be done this time.
Thanks

yes, and in my case especially since I didn't dyno, I run widebands all the time to keep eye on that stuff...what it does on a dyno and in the boat are 2 different things...in the boat being more important

How much timing are you running in this engine ?

Inconel or not, if mixture is lean, or timing to far retarded, or very narrow seat widths,, the exhaust temps can get out of hand real quick, and the valve can fail.

My guess, and its just that, a guess, is that the mixture is too lean, and possibly not enough timing. Many guys think timing is a tool for reducing power, adding safety margin, etc, but it is not. Its simply a point at which the plug should be fired for optimal combustion. There are many factors involved to what that number may be.

yes, many guys think less timing is safe, not always the case... we used to retard timing to make EGT higher to get out street cars past emissions....

Yep. Too much timing is a good way to fail emissions tests

38 degrees at 4k. I'll check the paper work but I believe that was it. He gave me the number and insisted I check it and set with my ignition box which I did.

did you ck the AFR's with a wideband on the boat ? looks like it ran lean as hell to me...that just happened to be the 1st cyl to say I'm out or here...

i am wondering how you say it looks lean compared to the other cylinders.i only see one exhaust port in the picture.

All exhaust port looked the same. The camera flash makes it look different.

No they were only checked on the dyno.
In the boat with my headers and my ignition box was the only differences my fuel pump also. 6.5 to 7 psi on the fuel pressure

The headers were pressure checked and were fine I checked them again after the incident still no leaks.

Unfortunately, a dyno pull, may not show a part throttle lean spot in the carb.

What carb do you have on it? I think the only way the A/F would go lean is if somebody played with the emulsion or the air bleeds. That controls the start of the boosters. Have you checked your fuel line from the tank to the pump?

you better put 02's in when you go back together, you might be surprised..I know I was on our setup...

Well finally went to check on my engine. Lifter stuck on the intake valve and the rest you can see. Checking their build sheets it appears the lifter bores were tight. So the human factor strikes again. The bores were measured and recorded and some how missed getting fixed.
The builder is stand up man and is taking care of it.
We had a good discussion about oil. No more off the shelf street oil for me. It was a brand name synthetic.

if it had a tight lifter bore no oil is going to fix it.

Yes my point exactly. My statement about type of oil was sarcasm.

the picture you posted shows a broken exhaust valve but you say it stuck an intake lifter in the bore.was the head also knocked off of the intake valve?

Yes both valves were broke. I did not take it apart. I borrowed a bore camera from work and checked it out before I took it to them. He told me the intake lifter stuck and started the carnage. They had to use a slide hammer to remove it.