I am looking for the blueprint dimensions to locate the four additional head bolt holes in the block and heads on a big block Chevy. I have searched every book that I have, including the Chevrolet Power: The official Factory Performance Guide! book. The Chevrolet Power book, as well as several other big block Chevy books, describes adding the “missing” head bolts to cylinders 2, 3, 6, and 7 of a production block, but none give the dimensions. In looking at the accompanying pictures in these books, it appears that the holes, which I have located at 7.20, .85 and 16.88, .85 are inline with the other head bolts located at 2.36, .85 and 12.04, .85. In my drawing, that places the “missing head bolts” inline in y axis and 4.840 (bore spacing) in the x axis. This location also places the bolt approximately centered in the port.
In the past, I know factory aluminum heads have used this procedure, adding four 3/8-16UNC socket head cap screws. Some books recommend a 7/16-14UNC. I have been looking at my 188 heads and I can not tell if there is a water jacket in this location or not. Is this procedure only for the aluminum heads, or will it work with cast iron heads?
The reason I am asking, I currently have my engine apart to investigate a water in the oil issue after an overheating issue while running at Aha Quin where I ended up with a blockage in the odd bank water jacket. I am running copper head gaskets with stainless steel o-rings. There is evidence of combustion gasses weeping in #3 towards the lifter valley, but no evidence of water leaking. I ran a compression test and all cylinders were within 5PSI, but the leak-down was at the low end of the acceptable range. It appears that this is resulting from lack of ring seal due to some corrosion pitting in the cylinders. Also, I was not able to do the leak-down test hot as the engine is not currently in a running condition right now.
Even though my head gaskets were not actually leaking (yet), I would like the added clamping force that these bolts provide.
Thank you in advance.