Cracked head....

[DansBlown73Nordic]

I just got a call that one of my 990 heads is cracked in two places. They are both in the valve seat area. One seat can just be changed but the other is cracked under the valve seat. I guess it can be pinned. I hope this fix will last for a while. :frown:

[sleekcraft76]

that sucks!!

[Bow Tie Omega]

Ouch!!

[LakesOnly]

This is an old school repair that is still not too uncommon, when this type of crack rears it's ugly head.
Make sure the machine shop understands that this time around, their repair is not for a passenger car engine (or even a 10 second drag car for that matter) and that he must be able to reasure that his repair will hold up in a marine-use, sustained 4000-up rpm application.
LO

[Fiat48]

While there is probably somebody somewhere that can fix that cracked head, and maybe the machine shop that has it now can do it, I'd worry about that SOB dropping the valve seat. I would get another head. Or take this opportunity to go to aluminum heads. But that's just me.

[LakesOnly]

Indeed, the above is good, prudent advice. I have to add to my last post that while this type of repair is an option, I would not want it in my motor.
Too bad this had to happen to a 990 head.
LO

[Infomaniac]

The Edelbrock Marine aluminum heads are only about 1,500.00 with inconnel exhaust valves.

[Blown 472]

Originally posted by Dans66Stevens
I just got a call that one of my 990 heads is cracked in two places. They are both in the valve seat area. One seat can just be changed but the other is cracked under the valve seat. I guess it can be pinned. I hope this fix will last for a while. :frown:
Find another head, dont waste you time putting seats in it, boats have such a big temp swing that seat will fall out and then you get towed back in by an 8 horse tiller flat bottom with guys in camo.

[wsm9808]

Originally posted by Fiat48
While there is probably somebody somewhere that can fix that cracked head, and maybe the machine shop that has it now can do it, I'd worry about that SOB dropping the valve seat. I would get another head. Or take this opportunity to go to aluminum heads. But that's just me.
I'm not sure I understand your logic on this one. With the repaired heads he would only have a couple of press in seats installed. With aluminum, all 16 seats are press in seats, and the aluminum has an expansion rate of roughly three times that of the seat material while the iron heads have the same expansion rate as the seat material. Seats will drop from an aluminum head way before they will from an iron head.... if both are properly installed.
I'm not saying aluminum heads are bad. I would rather run a new set of 315AFRs than the 990s any day. But seats do not weaken a head. Manufacturers have used seat inserts in production heads for decades to make heavy duty heads out of stock castings for use on 3/4 and 1 ton trucks. check out the iron heads from Dart, pro lighting, World, etc, they all have seat inserts on the exhaust side.
Oh, never mined, just go buy some new heads and send me those 990s so I can scrap them for you

[Fiat48]

I am aware alluminum heads have seats. I'm also aware that many cast iron heads have seats. I am also aware of expansion rates and valve seats are pressed in. I am assuming the crack is under the valve seat as he posted. You figure out the rest.
As I said, just my opinion.