Interesting flaw in early aluminum heads.

While working on my engine, I noticed a surprising flaw in the design of the early ('36-'37) "Lynite" aluminum heads. Long story short, the water channel holes in the head do not corrospond 100% with those in the block. I assume this problem was corrected in later years? In any case, check out the attached pics.

Cecil, that is intersting. The water passage at the rear of the head is really off. The diameter is right but mis- located. The same water passage at the front is correct. It is intended to be smaller. I guess the idea was to get more water to circulate to the rear of the block to help even out the temperature. All cast iron heads have the large passage at the rear and the small passage at the front. Knowing how these engine can overheat I think I'd try to get that "new" hole next to the mis-placed one closer to the size of the original using the head gasket to locate it. Lucky you caught this. What is perplexing is how they designed the cooling system passages. Water flow was controlled in 3 ways on these devils: Size and shape in the block, size in cylinder head gasket, and cylinder head.

Hey Peecher -- The small front hole was actually added *later*; it's not even there on my spare set. Thanks for the info on the back passage. I may try to open it up some before installing the heads.

Cecil, what are the casting numbers on these heads? I suspect there were some "running" changes made during the '36 to '39 models. Dee

Hey Dee -

Got them mounted now, but they were "H" part numbers. I don't recall seeing an engineering change suffix on the end. In any case, after copper spray-on sealant and high-tack hi-temp sealant, I still have a leak, albeit it small, at the top back corner of the driver's side. The closest plug was dry, so it wasn't leaking into there, but I still have to seal it up.

Sure sounds like there may be a small ( hairline?) crack in the cylinder head near that upper water passage? Might be opening up when you tighten the head? There is a "recess" on the rear of the block near the bottom water passage but evidently you are not getting a leakage there. Dee

how about old poor quality repair and redrill. the heads are mass produced on a mill....standardized... over 60 years

they have been repaired, take them off ..take them to a modern machine / engine shop.

I am sorry, but it is common.....look at your old twotz.

Read the story about aluminum..it wasnt very good when new....and is prone to failure.

jb