Head Repair Question

[SCrescue]

I have a damaged '78 large port head that I've so far been unable to replace. I'm starting to think in terms of repairing this head as an alternative to locating a suitable replacement. I have access to expert welders where I work (military aviation industry certified).

I haven't approached them yet to assess feasibility of a possible welded repair, thought I'd check the board first to see if anyone has tried to repair this type of damage and how successful it's been before going this route. Damage is inside the intake port, casting surrounding the guide has broken away, presumably when new guide was installed (didn't notice it when work was performed last year).

Please don't state the obvious, I know I'll have to at least partially disassemble the head and remove the intake guide first.

If the weld can be effectively built up to approximate the missing casting, then is it possible to be reshaped with a rotary grinder and redrilled for a new guide? Is this reasonably doable? Admittedly not much room to work inside the port, but at least its a large port head...

Mike...

[Rot 911]

You might as well give it a try. The head is worthless as is. I wonder if you can leave the guide in there and build the weld up around it? Then you would not have to try to drill the weld to make the guide fit.

[cgarr]

Your going to want to remove the guide, a good welder can build that area back up, you will then need a new guide and cut the seat again.

[Peter Zimmermann]

Engine Machine Service (EMS) in Los Angeles can fix that head and return it to you with new guides as though nothing had ever happened to it. Talk with Bill or Dick at (310) 641-7019.

[SCrescue]

Thanks guys, I appreciate the feedback. I'll give EMS a call.

Mike...

[briancoates]

Remove the guide get in there with a die grinder and smooth the broken area, take it back to the port shape as if it was never there. Put in a new guide, cut seat and drive. So you might loose a fraction of a HP, you will never notice.

[SCrescue]

That's a fair amount of aluminum no longer supporting the valve and guide...I'm more concerned about the valve becoming unstable than any change in flow or loss of power. If it was just a beater I'd probably do just that, I've got too much invested in this rebuild now to consider it. Thx

[304065]

The metallurgy of the head will be permanently altered, it's a paper weight.

OK, 956 or 962 heads had a "squish area" but I'm not sure that was welded, it may have been machined from a blank casting from Mahle. Plus race heads probably got changed after every (professional) race.

[Peter Zimmermann]

Originally Posted by john_cramer

The metallurgy of the head will be permanently altered, it's a paper weight.

OK, 956 or 962 heads had a "squish area" but I'm not sure that was welded, it may have been machined from a blank casting from Mahle. Plus race heads probably got changed after every (professional) race.

SC: Based on personal experience I don't agree with the above. Over many years, 25 +, we repaired so many heads that others had "repaired", and blown out ports at the guide because they didn't; (1) heat the head to achieve the correct press, or (2) machine the O.D. of the new guide to the correct dimension. We did heads in-house for many years, and since I closed the machine shop have had a number of them done by my referral, and have not had a single failure. EMS has even restored damaged combustion chambers for us, which involved removing both seats, welding and machining the chamber, and installing two new seats. Same story - no failures. I'm sure, like everything else, the quality of the welding is paramount regarding these repairs, and I'm quite sure that if the welds are not done by an expert the result might be very different.

[SCrescue]

Fortunately, lady luck has smiled upon me. I've found a replacement and will not have to do the welded repair...

Thanks for the valuable feedback guys!

[Peter Zimmermann]

Originally Posted by SCrescue

Fortunately, lady luck has smiled upon me. I've found a replacement and will not have to do the welded repair...

I know that you didn't ask, but be sure that you have your machine shop put that replacement head in their vertical mill, with the two existing heads that will be used on the same side, and have a clean up cut done to insure that it's the same as the other two. Quickest way to end up with a head leak, or a binding camshaft, etc., is to use a mis-matched head that's not cut to the same depth!

[SCrescue]

Thanks Pete, I'll make sure I match the heads.

Mike...