I have a 26-27 high head that has a defect, probably caused by a core shift when cast. The rear water jacket hole is a good 3/16" of an inch, maybe a 1/4" shorter on one end than the the gasket hole. The front jacket hole lines up perfectly. Also, the rear water jacket hole is 1/8" narrower than the gasket hole. I don't have a mill, but a do have an angle grinder and a Dremel tool. Should I worry about this defect, or try to open it up as much as I can?
I know high heads are a dime a dozen (except on Ebay) but I don't have time to get another 26-27 head in my possession and I just had this one milled .050, so it would be a waste of money not to use it. Any suggestions?
Can you relieve the hole in the head
That's what I thought I'd try with the small angle grinder or the Dremel tool, although it would be time consuming with the Dremel.
Terry, casting holes in blocks and heads often don't match gasket holes in virtually any engine block or heads that are of the poured cast variety. It is not a big deal as long as nothing is blocked by the gasket (if the hole in the head is covered by more than half the gasket for example).
But, opening holes to match gaskets (leave slight smaller than gasket opening) is in my opinion a good idea--in engines with water pumps. In a thermoshipon system, it my show minimal results.
In my experience with water pump engines, basically anything after a T, there is a potential to reduce coolant temps when water isn't disrupted by casting flaws and is free to flow smoothly in the passages. Again though, if you clean them up, make the holes slightly smaller than the opening in the gasket, corrosion still is happening on those castings.
With so many things to work on on a "T", this is not a place where I would worry or spend any time. I doubt seriously that any alteration could be felt, seen or measured.
Just make certain the head gasket is on in the correct direction (also becomes the up and down). There is a slight difference in the passages front and rear, but the head gasket can and many times has been put on backwards, and does sometimes work that way. I have seen them lined up so that one end "looks" okay, but the other is "off" a bit. Check the line-up both ways.
I would not worry about. Plenty of water will still move through the opening. It will not be a problem.