Aluminum Head Repair Questions

sanborn

sanborn

Senior Member
I am in the process of restoring a pair of GranCor 8ba heads. They are in horrible condition, obviously abused during the dirt track wars of the 50s. They were warped, so I milled them about .015" to get them flat. After milling, I saw two cracks on the rear cylinder of the left head and five cracks on the front cylinder of the right head. The cracks are very faint and all cracks are from the water passage and a stud hole.

I am going to "V" and TIG the cracks. But I can't see how far down the cracks go in the stud hole. I see two possible alternatives: 1. Bore the stud hole oversize and sleeve the hole with a thin aluminum tube OR carry the heads to a head repair shop and have heated Silica circulated through the head. Does anyone have suggestions?

In my earlier life, we had many aluminum blocks and heads repaired with Silica-----always sucessful. I lean toward that method but will listen to alternatives.

HELP!
 
Weld the cracks you can see and pressure test. You can always go to the silica process. JMHO
 
Weld on a corner first as some of the early castings are a real crap shoot when it comes to a nice alum weld.Some don't weld well at all.
 
The "Silica Process" is a repair technique I learned about several years ago. First plates are bolted to the heads that fit the bolt pattern----in my case a set of plates with the 8ba pattern. Next the head/plate combination is heated in an oven to 180 degrees, the heads are removed and heated Silica(also known as "water glass") is pumped through the heads. The silica is under pressure and pushes through the crack and gradually stops the leak. The pumping takes about 30 minutes. If the heads are still leaking, the pumping continues until the leaking stops.

I use Dover Cylinder Repair in Chattanooga, TN. Their phone is 423/624-5161. I have had sucess before with leak repair using their system. As a point of additional interest, a lot of race aluminum cylinder heads have this same technique applied, especially in the early Nascar days because the silica coating also helps the keep heat in the combustion chamber----in other words, a "Speed Secret"!

I called Dover this morning, they still have the plates for the 8ba! And, they still occasionally repair flathead heads. If you call, talk to Randy or Joe----the old man that built the business.
 
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