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914World.com _ 914World Garage _ Head rebuild advice for 103mm cut heads
Posted by: nditiz1 Aug 22 2023, 07:36 PM
EDIT: Head is toast. Looking to source replacement ones.
So I'm tearing into the FAT perfomance 2.6 engine. I was going to try to run it, but before that went to perform a leak down and saw a gaping hole in #4 next to the plug. I just removed the head and it looks good other than previous welding I assume FAT did when the built the heads. There is little material amount between the camber and the edge of the head due to the cut of 103 P&C. Is this just the evil of hipo engines or are better options out there? Should I have these rewelded OR buy new 103 cut heads? Who out there is running big power?
Also I know Raby spoke highly about FAT engines, but damn did they love RTV.
Posted by: Mikey914 Aug 22 2023, 10:42 PM
I'd start with new metal. Only way to know for sure you will not have issues in the future in this area. Had to have been real loud.
Posted by: technicalninja Aug 23 2023, 10:50 AM
That's TOAST in my book.
Wow! that had FIRE shooting out of it...
Those heads are "organ doners" for me and I'd be real nervous about the valves in the destroyed chamber.
Posted by: Mikey914 Aug 23 2023, 05:39 PM
Yes thermal failure “crystallizes “ that’s why you don’t know to what extent the damage is. More than likely, and if you could definitely identify, a significant portion would need to be removed, and additional machining and welding costs would outweigh any savings, with a big question of how long will the repair last?
Posted by: rhodyguy Aug 24 2023, 08:00 AM
Does this mean the case was opened up for the 103 clys?
Posted by: nditiz1 Aug 24 2023, 10:58 AM
Does this mean the case was opened up for the 103 clys?
It was, so I can't really go down to a more manageable size.
Posted by: Mikey914 Aug 24 2023, 01:02 PM
Size is ok, add additional oil capacity with an offset cooler and a temp gage. I wouldnt go any bigger, but its managable.
Replace the head and drive. 
Posted by: porschetub Aug 24 2023, 03:53 PM
Size is ok, add additional oil capacity with an offset cooler and a temp gage. I wouldnt go any bigger, but its managable.
Replace the head and drive.
Don't think it just as easy as bolting on another head,expect you need to get FAT to make another one up to match the other side ,numbers on the head would indicate specs I would say ?.
Then there is the question of how long will the remaining head hold up if the combustion floors are really thin as the OP mentioned ?.
Perhaps a reduction in CR may make them last longer but don't know in this case .
The effected cyl looks to have been running lean but hard to say if that was caused by the hole or detonation previously.
Remember back when I bought a set of heads off a well known builder in my country and needed them flycut for compression increase and he mentioned you can't cut then too deep with the big cylinders but with mine that was not an issue.
Don't think the solution is that straight forward.
Posted by: rhodyguy Aug 24 2023, 06:17 PM
Buy an unaltered case.
Posted by: Mikey914 Aug 24 2023, 06:39 PM
Size is ok, add additional oil capacity with an offset cooler and a temp gage. I wouldnt go any bigger, but its managable.
Replace the head and drive.
Don't think it just as easy as bolting on another head,expect you need to get FAT to make another one up to match the other side ,numbers on the head would indicate specs I would say ?.
Then there is the question of how long will the remaining head hold up if the combustion floors are really thin as the OP mentioned ?.
Perhaps a reduction in CR may make them last longer but don't know in this case .
The effected cyl looks to have been running lean but hard to say if that was caused by the hole or detonation previously.
Remember back when I bought a set of heads off a well known builder in my country and needed them flycut for compression increase and he mentioned you can't cut then too deep with the big cylinders but with mine that was not an issue.
Don't think the solution is that straight forward.
It really should not be too hard to use new metal and machine to match. I would find a reputable machine shop and go from there. Unless it’s under warranty.
Posted by: crash914 Aug 25 2023, 07:32 AM
I have at least one set of 103 cut heads. A couple of small cracks around the valve seats. I also think i have a couple of rebuildable core heads for stockish cylinders.
You are welcome to swing by and take a look.
I should be home all weekend except for a dump run Saturday early am.
herb
Posted by: Al Meredith Aug 25 2023, 08:59 AM
If I remember correctly Jake didn't like 103s because the cooling fins are smaller than on a stock engine in order to fit under the stock cooling tin. Since they fun hotter it is necessary to use a remote oil cooler. He told me that a 2056 is about the biggest you should go with a stock oil cooler. I've talked to Len Hoffmen about welding a crack on an aluminum head . To do this correctly the head mist ne warmed to 1000 degrees F ( I could be wrong about the temps) do your welding and then bring the head back very slowly . Just my 2 cents. Al
Posted by: nditiz1 Aug 25 2023, 12:07 PM
Herb! I totally forgot how you love running the hipo T4. Might stop by Sunday, I'll text you.
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