Just curious what the factory bolt length was.

 

Were all the thermostat housing flanges the same thickness? I thought the original aluminum(?) one on my 70 was thinner than the iron replacement, but it’s been 40 years so maybe that memory is inaccurate.

My thought is the bolt length may vary depending upon the housing.

 

In 1970 they were 5/16-18 x 7/8" per page 6-17 in the Assembly Manual.

 

Thanks, I was going to look through it, didn't think it would be in there. I picked up the Oldsmobile and an AMC Dorman replacement housing. The AMC is a bit taller and needs the holes tweaked slightly for the Olds pattern. Both are aluminum and the AMC has a threaded port, perfect for my cooling fan sensor. See which one works better. Now I know what size bolts I need.

 

If you're not worried about original look use studs in the thermostat housing.

 

Not a bad idea, will look up some studs.