radiator bolt size?

[moveoverGM]

Hi guys. I ordered a new fan shroud from Dennis Carpenter and will install it as soon as I find the bolts that hold it on. There are 4 of them and were not there when I bought the truck. They go through the shroud flange into the radiator flange which is threaded. Does anybody know what size these bolts are. I have a lot of bolts but none of them fit. An M-6 is the right size but not the right thread. 1/4-20 is too big. Any help would be appreciated. Donald.

 

[fatherdoug]

Size doesn't really matter(I'm sure I'll hear about that one) But seriously, the hole for the radiator shroud on the radiator is not threaded. As long as the bolt is small enough to fit through the hole, it doesn't matter what size you use. M6 is metric, which would be confusing, since all the other bolts would be SAE. I used a 5/16/20 "U" or "J" nut to attach my shroud to the radiator.

On edit, you said your holes were threaded. Mine were not. I would still start with either a 5/16 20 or 3/8/20. If you have a thread chaser, you could find out the size from that.

 

[Fellro]

Just looked at one here, and they are 1/4" sheet metal type screws.

 

[moveoverGM]

Interesting... fatherdoug, I was thinking of doing the same thing you mentioned. My problem would be getting the nut on the backside of the flange. There is not much room there but I could find a way if need be. I tried a bolt just slightly smaller than the M6. It slid right through so that size would work. Fellro, a guy who was looking at my truck suggested tapping the hole to 1/4-20. But that would involve buying a tap set and who knows when I would ever use that again!!
Again, thank you for the input. I am glad I am a member here!!

Donald

 

[Fellro]

With the screws I mention, no tapping required. It is not a 1/4-20, but a 1/4 sheet metal screw.
http://www.mcmaster.com/#99663a153/=13bnkig

 

[fatherdoug]

Also, the J nuts are threaded, so there is no need for a nut on the back side. Either way will work, as long as the shroud stays in place.

Here is a picture of my radiator, just for reference.

 

[Fellro]

Generally the j nuts have a much larger hole than the bolt needs, that way they can lock into the hole and stay aligned. The factory rad in the 78 I looked at had the holes tapered to give better holding to the screw.

 

[fatherdoug]

That makes sense. My radiator is aftermarket, but the shroud is Dennis Carpenter.

 

[moveoverGM]

This stuff is great!!
Thanks for posting these images. I am sure now that I can make this work!

Donald