Modifying headers

fastcatFredrik Gustavsson Owner of 6122

I removed the headers for installing bungs for the O2 sensors. I noticed that the port matching was very bad and the design of the collector wasn't any better, I will try to explain with a picture.
To solve the port matching problem I welded all the holes in the flange and drilled new ones in the correct position and shaped the ports in the flange to match the cylinder head. The ports in the flange were almost round and the ports in the head are more rectangular. I put a new piece of tube between the collector and the flange, this tube does not go inside the collector like the old one did.

Is this an aftermarket header or is this the correct one for a US GTS 1974?

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2/2/073:30 PM

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pittcrewOwner etc. of 3785

I had the same problem with a set of GTS headers I bought off of a guy with a GT5S. One side was slight ly off and the other side was a full third of a hole off.
I took a carbide burr and matched the port shape on the better side and then reshaped the tube and tig welded it. The Bad side I slotted the header bolt holes to move the port over. I had to weld more material on the flange because the slots went past the flange. Then I reshaped and welded the ports like on the other side. Its not perfect but it is much better.
Mike Drew was in town at the time an visiting the shop and he said that these were the worst headers that he had seen.
Mine were also very crude looking in the collector area so I cleaned that up also. I also had a fitting problem with the fuel tank shield so I had to put a small depresssion in the tube that runs by it.
Welding the pipes was tricky because of all the rust and contamination in the flange area that had accumulated between the tube and flange.
I tried to post pics of mine but this window wont let me do that. Good luck on your modifications

2/2/074:55 PM

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fastcatFredrik Gustavsson Owner of 6122

quote:
Originally posted by Pittcrew:
I had the same problem with a set of GTS headers I bought off of a guy with a GT5S. One side was slight ly off and the other side was a full third of a hole off.
I took a carbide burr and matched the port shape on the better side and then reshaped the tube and tig welded it. The Bad side I slotted the header bolt holes to move the port over. I had to weld more material on the flange because the slots went past the flange. Then I reshaped and welded the ports like on the other side. Its not perfect but it is much better.
Mike Drew was in town at the time an visiting the shop and he said that these were the worst headers that he had seen.
Mine were also very crude looking in the collector area so I cleaned that up also. I also had a fitting problem with the fuel tank shield so I had to put a small depresssion in the tube that runs by it.
Welding the pipes was tricky because of all the rust and contamination in the flange area that had accumulated between the tube and flange.
I tried to post pics of mine but this window wont let me do that. Good luck on your modifications

Did you notice any differences after the modification?

2/3/0712:14 AM

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yngve2483Member

quote:
Originally posted by Fredrik Gustavsson:
quote:
Originally posted by Pittcrew:
I had the same problem with a set of GTS headers I bought off of a guy with a GT5S. One side was slight ly off and the other side was a full third of a hole off.
I took a carbide burr and matched the port shape on the better side and then reshaped the tube and tig welded it. The Bad side I slotted the header bolt holes to move the port over. I had to weld more material on the flange because the slots went past the flange. Then I reshaped and welded the ports like on the other side. Its not perfect but it is much better.
Mike Drew was in town at the time an visiting the shop and he said that these were the worst headers that he had seen.
Mine were also very crude looking in the collector area so I cleaned that up also. I also had a fitting problem with the fuel tank shield so I had to put a small depresssion in the tube that runs by it.
Welding the pipes was tricky because of all the rust and contamination in the flange area that had accumulated between the tube and flange.
I tried to post pics of mine but this window wont let me do that. Good luck on your modifications

Did you notice any differences after the modification?

Hi Fredrik or HEJ in swedish
Consider new headers for better match between the 4v heads (I think you have) and headers. Two years ago I had the similar headers as you and very restriktive mufflers it really made a diffrence when I replaced them whith PI big throut
Mine is a US 1972 Pre L