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purpose of threaded hole in block

2K views 6 replies 6 participants last post by  Bo's 55 
#1 ·
What is the purpose of the threaded hole in the driver's side of a 350 block near the rear and just above the oil filter? The threads are one inch deep but the hole goes inside at least five inches. Also what is the thread size? I want to plug it but a 7/16 bolt feels a little loose in the threads.
Thanks
 
#5 ·
The smaller hole just above the filter is for the oil pressure switch. it's a 1/8" npt hole. The other is just 7/16 threaded hole. I have just gone thru this. The oil pressure switch hole is difficult to see. What I found is that the oil switch hole on my crate engine 1985 design is smaller than older versions.
 
#6 ·
The pivot ball hole will be a straight thread, but it won't be 5" deep. It will be forward of the oil filter if even there.

The hole above the oil filter is as discussed, an oil passage. You have to put something in it - a plug, a switch, or a line fitting. Most of the ones I've seen are 1/4" pipe, but as said some could be different.
 
#7 ·
It does look like threads for a pivot ball. For an experiment I fed a length of green shrink tubing into the hole and found that it entered the cavity between the block and the flywheel that I could see with the inspection cover removed under the flywheel.
Thanks Guys
 
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