Primary tube size?
I've been searching the archives for header fitment and there are a ton of posts to weed through and everyone's fit seems to be different with similar set-ups.
When I bought the car, somebody before me had swapped out the 327 and installed a 454 but 30+ years ago without the internet, I didn't know about the difference in frame towers, cross-members, bell cranks etc... which weren't changed out as well. At some point back then I put in some Hooker 2 1/8" headers which fit fine and cleared everything great. Flash forward to the present, and after having the bent sub-frame switched out and all the SBC parts corrected with the proper BBC parts (Bell crank, Cross-member, Frame towers/Mounts) the shop that did the work dented the hell out of them to get them to fit.
So after researching the archives, I figured my best place to start would be determining the primary tube size that would best fit my combination before looking for header fitment.
427/4 speed/3.90 rear-end gears/10-1 compression
What is the formula for determining header size?
Thanks in advance, Jim