Technical 55 ford headers

I am in the process of putting a mild 351w in a 55 fairlane, my issue is I have gt40p heads. I bought a set of JBA gt40p headers and the passenger side fit great. The driver side however hits the steering box and the control arm. My question is will merging #6 tube into #5 cause me issues? They are 1 5/8” tubes.


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Here is what I’m thinking

 

There are probably some technical reasons that you should not do it (sonic harmonics, etc., etc. etc.) but I would bet there would be no noticeable "seat of the pants" difference.

 

I'm sure you don't mean to run both 5 & 6 thru the same primary, right?

 

Yes run them through the same, be it use a slightly larger primary tube and y them together or use the 1 5/8 pipe and merge them.


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I'm sure you know by the FO that those would be the last two cylinders that you'd want to share
a 1-5/8 primary.

 

I guess I’m confused how it would be much different than these manifolds?

 

Because manifolds are designed such that each short cylinder section immediately dumps into a much
larger diameter chamber rather than trying to share consecutive FO cylinders in a small diameter

 

I can’t help with header calculations, and I understand you’ve got a 351. But you might take a look at the headers Red makes for those cars with the y block. The interference on the front at 5 & 6 is the same. Thunderbirds and trucks don’t use the side motor mounts, and you can buy more conventional headers for them. But the pass car units all exit at the rear. I’ve seen custom headers on 55’s and they all followed the pattern of going back and then down. Depending on transmission, the column shift and clutch become the next problem, but that might be a moot point for you. Not a good answer, but maybe a way to think outside the normal box.

http://reds-headers.net/index.php?main_page=product_info&cPath=10&products_id=138