Seymour Snerd
Lifetime Supporter
The first few times I assembled GT40 Mk II headers to the FE engine in my SPF GT40 I struggled quite a bit, scratched up their ceramic coating, and then immediately forgot whatever it was I learned in the apparently random walk I took in determining the assembly order. Being 2-1/4" diameter there is very little clearance between the headers at multiple points so I suspect there is exactly one correct assembly order.
However, thanks to a comment by Adam Christian I just now successfully completed the operation without fuss, scratches, or procedural U-turns. Here it is in case anyone might find it useful. This procedure or some variant may also work with small-block headers, but I don't know. And they may be less difficult anyway given their smaller diameter.
However, thanks to a comment by Adam Christian I just now successfully completed the operation without fuss, scratches, or procedural U-turns. Here it is in case anyone might find it useful. This procedure or some variant may also work with small-block headers, but I don't know. And they may be less difficult anyway given their smaller diameter.
- It's significantly easier if the lower holes in the header flanges are slotted so the flange can be slid laterally onto the lower screw. My stock SPF headers are like that. I assume here we are using screws, not studs and nuts. Also, I am deliberately not referring to cylinder numbers, but rather will refer to the header positions relative to the each other, while facing forward.
- Start all eight of the lower screws in their holes in the head. If you do not have slotted lower holes you will skip this step and start the lower screws after the first four headers are placed.
- Put the four inner headers in place resting on the lower screws. Arrange their outlets to form a neat close square with their ends aligned. These headers form the two inner pairs of outlets and are the ones that do the crossing over which is why they have to be placed as a group. A bungee cord or large rubber band around all four outlets might help stabilize the assembly, although I did not find that necessary.
- If you are using a Felspro gasket or any other that has slotted lower holes, you can now slide it into place from above.
- Place the forward pair of headers in place. These occupy the outer lower positions in the outlet stack.
- Place the rear pair of headers in place. Thes occupy the outer upper positions. This completes the rough placement.
- Lightly tighten all the lower screws to bring the header flanges close to the head. You should now find the outlets all together almost enough to accept the collectors. In fact it may be a good idea to install the collectors now. I have not tried that yet.
- Start the upper screws in the two inner pairs of headers. You will probably find the rear-inner pair to be the most difficult due to the forward-inner headers passing close "over head". The most common problem for all positions is the screw shaft binding against the hole in the header thus preventing you from threading it in with fingertip pressure. It may help to have an assistant hold the header in whatever position allows the screw to spin into place. Or if you tighten the lower screw the header can probably be persuaded to stay in that position.
- Once all the screws are finger tight, you should put the collectors in place.
- Tighten all the screws. I recently purchased a set of Craftsman "ignition" (i.e. "small") combination wrenches (#42319, $20) and discovered that because they are stamped from ~0.1" sheet metal and have a 12-point box end they are absolutely perfect for tightening the header screws where there is little axial clearance above the screw head. Hex head screws should take a 7/16" wrench. 12-pt heads should be 3/8".
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