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.:rolleyes:

[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.

[wsm9808]

was not trying to make an assumption as to what you know or dont know, or chalenge your opinion Fiat. I just used your Quote to set up another point of view and add some more information to the subject of this tread. Sorry if it came out sounding like I was disputing your post.

[DansBlown73Nordic]

Today I spoke with the machine shop to find out the guy has never done this type of a reapair before......:eek: But is just getting into doing this and has a guy from the repair factory coming to show him how the system works.....My head is the one they are going to practice on.......:mad:
Im pretty sure im not going for this. I have another guy who does nothing but fix cracked heads. I think I will just have him fix it...;)

[gnarley]

Originally posted by Dans66Stevens
My head is the one they are going to practice on.......:mad:
Im pretty sure im not going for this. I have another guy who does nothing but fix cracked heads. I think I will just have him fix it...;)
Good idea regardless on how they end up being used. I wouldn't want anyone practicing on any of my parts. Cracked head repair is a little bit of art and science, the more experience the person has doing it the better the chances of a good competent repair.
I did a little bit of cracked head repairing about 30 years ago and learned from a master, it was great to learn how to do it but I might always wonder what might happen if run in a boat but I do have to agree with wsm9808's logic. If the repair is done correctly in theory it should be fine, even in a boat with pressed in seats.
As long as the seats have been peened over with the head material in a few locations with a center punch I don't see a reason for the seat to ever drop due to the additional force being exerted on the seat and the crack should not start moving again IF the machinist drilled correctly on both ends and sealed the tapered bolts correctly and tightened the hell out of them before the reshaping & machining.

[1979tarva]

http://www.locknstitch.com/CastIronWelding.htm
heres a link to a place that explains how to repair a cracked head if anyones interested in it

[hulshot]

66stvens, I can solve the problem quickly. I have merlin d-ports with big vavles set up to run. no machine work has ever been needed or done. intake porting and k 900 springs with all good stuff. send me a check and I will get them out to you in under a week so you can be on the water soon. they only have 10 hours on them with new valves, springs and guides. good luck on whatever you deceide.

[230EAGLE]

I am a full line machine shop, specializing in cracked cylinder heads. I hot weld all cast iron, I do not use pins. We repair them with pure cast iron. They are as strong or stronger then the originals. All are work is guaranteed. If you have any questions please give me a call 559-822-6500. I can further explain the process to you.
Erik

[JetBoatRich]

I know the feeling, cracked a 990 head a couple weeks ago:yuk: