I was getting a set of heads reworked for a ragtop 68 firebird and took them to the machine shop to get the guides and seats done. Well he called me today and said there was a probem with one head, it has a hole about the size of a pencil lead about halfway between the guide and the exhaust wall through to water. The heads were ported before I got them and it's probably pretty thin right there. These head castings are kind of hard to replace as they only made them two yrs. in firebirds and gto's. I hate to go welding on them as it could ruin the head. I there any kind of epoxies that will hold up in a exhaust port? I think if I could get it closed up maybe something like mendtite or the old egg glass sealer would hold it. I was running these heads on a sandrail a few yrs back and they didn't leak then, so I really don't know what happened but I sure would like to fix it.

 

Bummer!!!! I doubt if the epoxy type repairs will hold up very long. Call around for used first. There are a couple welding shops I know that weld heads and blocks with cast iron and remachine them. It's a unique process. He guarantees the repairs too. A lot of antique restorrers use the one in Mich, but I don't remember the other guy, out west here someplace. If you want his number let me know and I will look for it.

 

it CAN be fixed... if it was the intake side it'd be no problem... a little JB Weld, and you're on your way... exhaust side needs to be welded, and it's gotta be done RIGHT.

 

Another DTR member just told me about these rods, which may be useful in your situation:
http://www.muggyweld.com/

Chris

 

Yea, I'm real sick about it, they simply can't be replaced today. I have several sets of regular pontiac heads but this set has a different exhaust port layout on it and sticks out to a pontiac person. I'm not giving up, I really think it can be fixed as it such a small spot but I hate to use much heat with it being so thin. To replace this one casting IF you can find someone willing to sell one is going to be at least a thousand on up. I haven't checked but I don't think any epoxies will stand the heat. From what I'm read the metal at this shouldn't get over 500 degrees but it is one of the hottest spots cause the gasses are being pushed out and riding the roof right on this spot. Thanks Gary

 

I had some radically ported 440 heads and encountered the same thing. I tried about 6 different epoxies that were "guaranteed" to work-NONE did. I welded them and all is good 5 years later!!

 

What kind of welding process did you do? I'm going to check with a jeepin friend who is a wizard with a tig welder and see if he thinks that's the way to go. Might use a heat gun and warm the port up real warm and then just hit the one spot with a tig. The heads have been hot tanked and run through a shot machine so they look brand new. Mcmopar, how thin was the casting where you did the welding? Thanks, Gary

 

Used an arc welder with real small rods, 99% nickel, heated the head up first and let it cool down real slow. Wall thickness was about .090 to .125.

 

How about brazing it? The hole sounds small enough and brazing will stand up to the heat. I've brazed other broken exhaust parts before with 100% success. You'll need to preheat the piece in an oven for a couple of hours to heat soak it then braze up the hole with a tourch.

Any thoughts from others?

 

I've been thinking all day and I'll run this by the majority. Drill the hole out round, then tap it for say the smallest bolt I can. Run it in and peen all around it. I think there is enough metal to do this then maybe just spot it on top with a wire welder. I think if I run a good sealer like mendtite I know it will seal around the threads. Maybe not even tap it just find some rod or bolt the right size and tap it in then peen it on outside. What do you think? I am open to any suggestions! Thanks Gary

 

I don't think it will hold. IMHO.

Have you thought about brazing it?

 

I have but I was hopeing for something where I don't have to heat the head so much. It will probably go that way cause it looks like its narrowing down to that. I'm just afraid to weld on it, if it blows out it is pretty much done for. The guy at the machine shop is checking on what they call spray welding but that is a long shot, I think it requires heating the head to a high temp. At least if it fails after I put it together it will just go out the exhaust and not make a grinder out of my shortblock! Thanks Gary

 

I've seen lots of heads spray welded to bring them back to an acceptable thickness to be reused. I don't know about repairing a hole using spray weld.

 

I think brazing would still put too much heat into it. Stick weld it w/ a 99% nickel rod. Preheat to 250-300 degrees or so. If it's welded right you should only have to have the arc heating it for 2 seconds. Immediately after it's welded tap it w/ the round side of a ball-peened hammer (called peening). That'll relieve the stress in the spot weld. After about 10 seconds of peening, the whole piece needs to be put into a heat source (kitchen oven, preheating oven, etc) at around 300 degrees to keep it at a hot enough temp so no cracks form. The oven needs to be slowly cooled down over a few hrs time until it reaches room temperature. That's one of the super-safe ways to fix it...that would almost guarrantee the fix will hold up.

I like the idea of spray welding too. If there's 1 hole, who knows when or where another hole will appear. Maybe you better build up the whole piece w/ spray welding while you have the engine broke down. I'm not sure if it's possible to spray weld cast iron though...I'm not sure what they'd use besides nickel.

 

Welder27 has the plan!

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