Header bushings?

[VadersV6]

I got my new drivers side header (old one is cracked 8 ways from sunday). The bolt holes are huge. How in the world are the ports supposed to line up? Anyone ever install bushings? I'm a machinist and have a whole shop here, so I dont see why not. What size are those bolts? 1/4"?

 

[Lee Thompson]

bolts

The thread size is 3/8 in the head. The hole size in the header flange is 1/2 in.
I use shoulder bolts to line up the flange perfectly. 3/8 in. thread with a 1/2 in. shoulder.

 

[VadersV6]

Thanks. Based on memory, I was thinking they were 1/4-20. I actually have some 3/8-1/2 socket head shoulder screws here at work. Maybe I'll try those out.

 

[Ormand]

It may be that the holes are deliberately oversized, to allow for the difference in thermal expansion between the heads and the flanges.

 

[Lee Thompson]

maybe

I just use them for location untill I get some of the tops one in and tight. Then remove the shoulder bolts. I assumed the over sizes holes were for ease of install.

 

[VadersV6]

Yeah I would think it would be there to speed up the assembly line. The steel does expand, but not that much. I'm just going to run 1 bushing in the center top hole. That way it can still expand, yet stay pretty much located.