Header help please

[D Stand]

I am at the point of getting a set of headers and need some guidance from whoever has worked through my issue before. I bought this Mk4 kit from the original owner that already purchased a ford racing boss 351 based 427 with “Z” heads. He had trouble with factory five getting a proper set of headers and what I have is 2 driver side Hooker headers for I think a 351w. This kit was purchased originally in 2015. In calling factory five, they do not want to help with anything other than stock 351w heads. They did give me a number for GP headers to get a custom set made. Zach at GP says he is no longer making headers for factory five anymore but told me that most aftermarket heads have the same bolt pattern but the port itself is raised up. So I bolted up the driver side and it looks like I would need to cut about 1” out of the top of the exhaust cut out. I know some opening up will be needed but is this normal or should I have a set made to fit lower to start? I took the gasket and put it upside down and the ports line up so my ports are higher than normal. Hoping someone has dealt with this before and lead me in the right direction..

Thanks Dale133337133338

[Gordon Levy]

Put a set of my lowering engine mount in and it will cure your woes.

[D Stand]

Thanks for the input. My oil pan is already at the bottom edge of the chassis. I also need to buy a set of headers anyway as I do not have a passenger side. I also added a sniper efi so need a set for O2 sensor too.

[Norm B]

I have a set of 351 heads on my 331 and had the same issue. I had the header flange on the drivers side machined at an angle to lower the side pipe end about an inch. You can determine how much you need machined off the bottom by installing the header, without the gasket, and just tightening the bolts until the flange is touching the head at the bottom and the side pipe end is at the right height. This leaves a gap between the head and the top of the header flange. I used feeler gauges to measure this gap and had the machine shop take that much off the bottom of the flange tapering to nothing at the top. Didn’t cost that much.

HTH

Norm

[Gordon Levy]

Call Georgie at Gasn pipes. You can get a set with 3" flanged and an adjustable collector so you can tune in the fit.

[GoDadGo]

Go-Dad's First Stupid Idea:
Would it be possible to partially cut the primary tubes (small wedge) at the bottom near the upper flange by the head in a straight line, pull the header down and re-weld?

Go-Dad's Second Stupid Idea:
Could you cut collector off and add a 4 into 1 slip-on or merge-style on collectors (See Shoenfeld Link) to bottom and add a side pipe mounting flange to the end?
https://www.schoenfeldheaders.com/collectorsy-pipestabs.html

I used Shoenfeld 161-33 and made them work, so I'm thinking a little surgery on either end of the header might get you there.
https://www.schoenfeldheaders.com/imcaump-modified5.html

My thought process went down these paths because nobody made headers for my car since I'm running a Small Block Chevy that's been moved within the chassis.
I've got customer headers, custom driveshaft, custom engine & trans mounts (which have been moved forward) and I'm not a mechanic or professional fabricator.

Naked Cobra:
https://youtu.be/V38Jajo_qOQ
Finished Cobra
https://youtu.be/9WEe6-wdNtA

If I Can Stuff A Chevy In A MK-4, Then I'm 100% Certain That You Will Overcome This Issue!
.................You've got a problem that you'll be able to overcome, you just don't know which path you want to take!
.................Personally I think cutting a small wedge at the top, pulling them down, then rewelding the closed gaps may be the easiest option.

[GoDadGo]

I have a set of 351 heads on my 331 and had the same issue. I had the header flange on the drivers side machined at an angle to lower the side pipe end about an inch. You can determine how much you need machined off the bottom by installing the header, without the gasket, and just tightening the bolts until the flange is touching the head at the bottom and the side pipe end is at the right height. This leaves a gap between the head and the top of the header flange. I used feeler gauges to measure this gap and had the machine shop take that much off the bottom of the flange tapering to nothing at the top. Didn’t cost that much.

HTH

Norm

I Think Norm's Idea Is The Best Option If The Flange Is Thick Enough To Machine!

[Greg K]

If you need them custom as indicated and need a passenger side as well, contact Stainless Headers: http://stainlesssteelheaders.com/cobraheaders

Thanks for the input. My oil pan is already at the bottom edge of the chassis. I also need to buy a set of headers anyway as I do not have a passenger side. I also added a sniper efi so need a set for O2 sensor too.

[GFX2043mtu]

133347133348 I had the same issue but I used Gasn pipes. My fix with Georgie was to cut the header about 4-5” back from the side pipe flange and weld in some new tubing that I had him make to my specs. I think they where bent at 15 degree but I’m sure he will remember. I then used a jig to hole the pipes true to the side of the car so then I could fit and tack the new pipe sections in place. One done I removed the headers and tig welded them on the bench. PITA but they fit perfectly. I even asked Georgie if hw wanted them for a couple weeks to make a jig from them for others with raised port 351w motors but he didn’t want them. Sucks for everyone else especially if you don’t have the skills or tools. 133346

[NAZ]

If you do go the custom fabrication route, find a shop that can calculate the correct size/length to complement your engine configuration and RPM operating range.

[D Stand]

Thanks for all of the input so far. Looks like GASN might be my best option as he knows these cars.