Cylinder Head Experts, Is This Crack Repairable?

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cruiserfj45

cruiserfj45

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While doing a valve adjustment for a customer, on a 91 FJ80, I noticed a glimmer of green in the sun. After pressure testing and cleaning the suspected areas I found this. It is located between the exhaust valves for cylinder 2 and 3. There is also a smaller one in the same spot but between cylinder 4 and 5 exhaust valves but the picture doesn't show it well. So has anyone been successful at having this type of crack repaired or do I need a new head. While typing this I inspected it again and find coolant under the valve spring. @orangefj45 @FJ40Jim @LAMBCRUSHER
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There are two answers to your question. One is academic, which isn't what you are interested in. The other is practical.

The only repair procedure that will positively seal that crack is welding. And yes, you can weld cast aluminum. However, there are very few people who can do it well, most of them work for foundries which cast parts for gas turbines and large marine diesel engines. None of these are job shops.

In this case, the coolant galley is below and between the valve seats and in order to repair this, you'd have to remove a small portion of the cast metal between the valves to expose the crack, and then weld the crack shut. The reason is that you have to know how far the metal has separated, in order to properly prepare the joint and ensure sufficient weld penetration. Even given these precautions, you may find that once the largest width is exposed, there isn't sufficient material left to work with.

The cost of the repair will exceed the cost of the replacement. I would be very interested in hearing from anyone who has experience repairing internal defects of this size on these heads, for less than the replacement value. I'm specifically referring to repair procedures which positively produce a condition equal, or superior to, the original casting.
 
With enough $$$ it can be repaired, likely better to replace. Cracking on the later F heads is pretty common, so may want to have a replacement crack tested before installing?
 
Can you still find them? I've never checked the market.
 
I know it's the customers vehicle and not yours, but I'd suggest they replace it only because to probably repair it you'd have to take the head off and cracks are know for spreading. For just a keep look it seems like you can get a head for $400-$500.
 
Mudder said:
I know it's the customers vehicle and not yours, but I'd suggest they replace it only because to probably repair it you'd have to take the head off and cracks are know for spreading. For just a keep look it seems like you can get a head for $400-$500.
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Is that new or used? Where are you finding them?
 
If it were me, and based on MY past experience, find a replacement head. Have it crack-checked and pressure tested. Then install it if all checks out.

Welding a head and then insuring it is good is a HUGE gamble.. i would ONLY go this route if the head was complete unobtanium and I was restoring some very special, unique, highly valuable vehicle. Not an 80. Way too many parts available.
 
There is just so much that can potentially go wrong with trying a weld repair. It is possible but not cost effective and the procedure would Involve removing the head, complete disassembly, caustic dipping and then prepping the crack, heating the head to an even temp, welding, reheating and gradually reducing the temp until cool and then grinding and any necessary machining of welded areas, then having the head magged or dye checked then resurfaced and reassembled and then reinstalled. Only way to insure it's going to last. And the crappy part is you won't even know until you open the crack up if it's repairable or not. So, I'd look into an new or good used head.
 
New heads are Gone Johnson so that option is off the table in any event.
 
When i ran my own shop, I'd pass on welding repairs like this. My reason, if you do the repair, you now own that repair. So remember, if you do weld it, and the repair fails, your customer is going to expect you to repair it again, maybe for FREE! Failures like this can damage your shops reputation, so it's a no win situation for a small shop.
 
Talked with the customer, he is on the hunt for another cylinder head. Thanks for all the advice, I was thinking that was the answer but I was grasping for a little hope.
 
Rifleman said:
When i ran my own shop, I'd pass on welding repairs like this. My reason, if you do the repair, you now own that repair. So remember, if you do weld it, and the repair fails, your customer is going to expect you to repair it again, maybe for FREE! Failures like this can damage your shops reputation, so it's a no win situation for a small shop.
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Agree 100%.

Risking your rep as a operating business -let alone rework possibilities- just don't seem worth the risk/reward. A replacement used head is the only solution I'd place my name on the invoice of. Their motor, their broken part.

The owner flat overheats his motor anytime in the next 12 months they would come back to this if the head is repaired, or whatever situation where their motor didn't run like a top & the head could possibly be blamed.

It would seem you'd be risking your rep & all the reward is maybe saving someone $3-400 tops. No thanks!

If it was your 80 - sure, do whatever you like. No reputation on the line (esp in this age of social media, you could become the "leper mechanic" in a day thanks to twitter, facebook, etc.).
 
@cruiserfj45 : J, I have a head, not sure on condition. hadn't wanted to sell it, but if it got someone out of a pinch...gimme a call...
 
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