Header Bolts for a 340

-

340inabbody

Well-Known Member
Joined
Jan 31, 2018
Messages
344
Reaction score
113
Location
Arizona
Hi what size bolt is used for my 1973 340 small block LA? My info shows it as a 5/16-18 but not sure of the length. I am not sure what headers I have but I think they are hookers.
Thanx
 
3/4" seems to be the typical length with a 3/8" 6-pt hex head. Sometimes it can be more convenient to leave the studs in the end bolt holes because they go into the coolant. Just make sure the headers can move enough to slide off.
 
3/4" seems to be the typical length with a 3/8" 6-pt hex head. Sometimes it can be more convenient to leave the studs in the end bolt holes because they go into the coolant. Just make sure the headers can move enough to slide off.
Thanks for the response. So 5/16-18 x 3/4 and I plan to use those nifty Nord-Loc washers.
 
3/4" seems to be the typical length with a 3/8" 6-pt hex head. Sometimes it can be more convenient to leave the studs in the end bolt holes because they go into the coolant. Just make sure the headers can move enough to slide off.
Or you can slip the headers in place, twist in a couple center bolts to hold them and the gasket in place and then seal and install the outside studs.
 
Or you can slip the headers in place, twist in a couple center bolts to hold them and the gasket in place and then seal and install the outside studs.
Is there a preference of the order for tightening? The headers are already in place but I am replacing the shity bolts that are there alteady (some not tight).
 
When you leave the end studs end with headers, once you get everything tightened down......you can saw the studs off so there are only 2 or 3 threads sticking out past the nut. That will make it easier to get the headers off without draining the motor.
 
Is there a preference of the order for tightening? (some not tight).

depends on the brand of headers.....some bolts have to go in before other...the inside bolts on the front and rear ports are space limited....do not tighten any bolts until they are all started..
 
When you leave the end studs end with headers, once you get everything tightened down......you can saw the studs off so there are only 2 or 3 threads sticking out past the nut. That will make it easier to get the headers off without draining the motor.
Hey JD “Without draining the motor” ? I don’t understand that part.
 
The end studs holes are drilled into the head coolant passages. If the studs come out and the coolant has not been drained below that level it will come out. If you remove these studs use Teflon tape or another sealant to prevent leaks on the end bolt holes on both heads.

Some aftermarket heads may not be drilled through to coolant but it is always best to check first.
 
The end studs holes are drilled into the head coolant passages. If the studs come out and the coolant has not been drained below that level it will come out. If you remove these studs use Teflon tape or another sealant to prevent leaks on the end bolt holes on both heads.

Some aftermarket heads may not be drilled through to coolant but it is always best to check first.
I use the Indian head shellac the stuff works great!
 
-
Back
Top