.0015-.002 if it was an extreme horsepower deal might want a little extra on the exhaust side of things...

^^^^^^^ i agree.

Found this to be a good read:


http://www.performanceboats.com/gn7-...arine-use.html

Post 13 &14 makes me believe this thread should be renamed whats wrong with AFR`s valve guide clearances instead of the current title.

Sorry about your troubles Tim.

How many run a valve seal on the exhaust? I don't and never have on a marine or anything that had any snot to it for that matter...

K making sure thx

Anybody ever measure their seat widths on their AFR heads, or any of the out of the box heads? Inconel valves are great and all, but seat width should be a consideration on a marine endurance engine as well, to aid in cooling of the valves.

So at this point it looks like Tim is concentrating on his valve guide clearance. If the valve seized in the guide, would that also cause the stuck lifter? Logic would assume it could if the valve was only partially open, but then I would think that it would be less likely for the valve head to be snapped off like that. My money is on the lifter galling up and seizing in its bore - which led to the damage to the valve.

Tim, does it look like that cylinder will require a sleeve? If not, you might be able to get away with a rehone and a new piston in that hole. The head could probably be welded up and fixed. It sounds like you were paying attention and shut it down in time to avoid further damage. It still sucks balls. Good luck with everything.

I am running the same lifters and heads in my boat. Now I am going to be tossing and turning at night wondering if I'm going to drop a valve the next time I take the boat out. :eek: I wonder how many of us are running the AFR heads out there out of the box without having checked guide clearance and exhaust valve seat width. :party-smiley-004:

I found some things that make me question.... Looking for answers trying to keep it off here for now, a select few know what's up, not a happy camper this week....

I have been informed within recent to have every head custom built by a trusted machinist local to you that you trust, 7 people told me that in last 2 days gonna leave it there....