On a recent performance build, when the customer filled the coolant system, the top half drained into the oil pan. Fortunately, he caught it before it before starting the engine.
He pulled the engine and we had it shipped back for examination. Also, fortunately, the problem was the easiest fix.
On ’61-64 V8 heads, Studebaker enlarged the oil drainback holes from 5/16” tp 3/8”. We always drill the early heads to that 3/8” diameter; at least fifty early heads and have never seen any problems. Randomly, recently, this 535976 head either had internal core shift or enough internal rust in the area of the drainback hole that it caused a pinhole to open from the coolant side when the drainback hole was drilled to 3/8”. The pinhole was down in the middle of the passage and not easily visible.
The fix we came up with was to drill the hole to 7/16” and press in a 5/16” valve guide. With a .002” press fit and Loctite, it’s a permanent repair.
As we drilled larger for the repair I was watching carefully and it was good to see the pinhole not get larger as we drilled the drainback hole larger for the repair. The hole stayed small, indicating a very localized problem area.
As a precaution, we’re pressure and vacuum testing the other head to ascertain there’s no similar problem hiding in there.
The engine will soon be back in place and we learned just one more thing to watch for when trying to improve this rusty old stuff.
jack vines
He pulled the engine and we had it shipped back for examination. Also, fortunately, the problem was the easiest fix.
On ’61-64 V8 heads, Studebaker enlarged the oil drainback holes from 5/16” tp 3/8”. We always drill the early heads to that 3/8” diameter; at least fifty early heads and have never seen any problems. Randomly, recently, this 535976 head either had internal core shift or enough internal rust in the area of the drainback hole that it caused a pinhole to open from the coolant side when the drainback hole was drilled to 3/8”. The pinhole was down in the middle of the passage and not easily visible.
The fix we came up with was to drill the hole to 7/16” and press in a 5/16” valve guide. With a .002” press fit and Loctite, it’s a permanent repair.
As we drilled larger for the repair I was watching carefully and it was good to see the pinhole not get larger as we drilled the drainback hole larger for the repair. The hole stayed small, indicating a very localized problem area.
As a precaution, we’re pressure and vacuum testing the other head to ascertain there’s no similar problem hiding in there.
The engine will soon be back in place and we learned just one more thing to watch for when trying to improve this rusty old stuff.
jack vines
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