Engine An Odd Engine Question

joekurt

Member
Oct 28, 2021
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18
Pennsylvania
So my son and I are working on a 1976 Ford 302. I built this engine about 30 years ago with the intent of creating a Cobra engine (Cleveland 351 heads on a 302 block). Unfortunately the salvage yard sold me a pair of 351M heads which were used mostly on trucks. However, to make that work, coolant flow is different through the 351 heads so an additional hole was needed in the 302 deck to match up with the coolant channel in the head. We are now going to get rid of those 351M heads and go with a pair of AFR 165s. I am assuming we will need to plug those holes in the deck since there is no corresponding channel in the AFR heads? Any thoughts on how best to do this would be greatly appreciated. Small freeze plug? Have it welded? Thanks all!
 
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So my son and I are working on a 1976 Ford 302. I built this engine about 30 years ago with the intent of creating a Cobra engine (Cleveland 351 heads on a 302 block). Unfortunately the salvage yard sold me a pair of 351M heads which were used mostly on trucks. However, to make that work, coolant flow is different through the 351 heads so an additional hole was needed in the 302 deck to match up with the coolant channel in the head. We are now going to get rid of those 351M heads and go with a pair of AFR 165s. I am assuming we will need to plug those holes in the deck since there is no corresponding channel in the AFR heads? Any thoughts on how best to do this would be greatly appreciated. Small freeze plug? Have it welded? Thanks all!
A NPT hex plug even with or below deck height would be my first choice.
 
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If memory serves, I think the block was supposed to be left alone but the heads had to have a passage blocked to work with the Windsor block? It's been a while, but I was going to do the same thing 20+ years ago. Even spent the money and bought an actual Boss intake manifold.

I had picked up some Modified heads too, I seem to remember them being the same exact heads as the earlier 2V Clevelands but had huge combustion chambers in comparison. The Modified part of the name came from the blocks changing to accept a big block bell housing whereas the Cleveland accepted the small block bell. Since they used the 4V heads on the Boss 302 and didn't change the architecture of anything other than what it would take to accept a different bell housing, I would think that you most likely wouldn't have had to do anything to your block.

I do know, however, that the block will need a coolant hole drilled IF you were to go with Trick Flow heads. The earlier blocks didn't have a passage somewhere near the center(?) and a steam pocket would form which impeded or blocked flow. In those cases, you would use the head gasket as a template.

I don't know where you are with your build, but I'd double check the deck vs the head gasket. Worst case scenario (in my mind anyway...) is that you'll have a passageway that is already blocked that you'll need to drill.
 
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I may not fully understand the question but if there's an extra hole in the deck without a matching channel in the head, and the head gasket covers up that extra hole, I don't think the coolant has anywhere to go so you wouldn't really need to do anything about it.