advert

Header Installation, Manual Choke…and More

302-headers

Pete Mantell’s headers

After trying a few different header ideas–a set from Sunbeam Tiger (left side worked, right side wouldn’t make it past the starter), a set from an early HiPo Mustang (neither side would clear the firewall), a set of reversed 302 shorties (wouldn’t clear either the oil pump or the alternator, and a set of tri-ys (left side would work with some cutting, right side wouldn’t fit no matter how much I rearranged)—I finally broke down and bought a set of through-the-well headers from Pete Mantell. I groaned about the cost $650) but truly, I could have bought the set and had money left over after all of my experiments.

MGB-headerdistance

Measuring for the outside dimension

The first order of business was to locate where to cut the fender well. Pete sent along a few photos that helped get me in the general location but I decided to measure for myself to see if I could minimize the size of the opening. I started by locating where the outer edge would go by measuring from the header flange to the collector, making note of whether or not the opening would be centered relative to the flange (the left and right headers are slightly different from one another). Once I had the rough measurements, next was to transfer them to the well.

Initial header hole

Initial header hole

What I ended up with

What I ended up with

My rough starting dimensions were about 4″ x 5″. I marked them out using a silver Sharpie, drilled each corner (3/4″ diameter), then cut between the holes. The first two things I discovered when trying to fit the header were that it wouldn’t clear the valve cover and that the my hole was way too small (Pete said this would be so). It took me about 3 more times, enlarging the area a little more with each attempt, before I had an opening that was large enough for the header to pass through. I also massaged the lower edge a bit to help with clearance. Withe the header finally in place, I fashioned a trim plate out of 16 gauge steel (painted black to match the wells) to clean up the opening.

Combination of bends

Combination of bends

Next was to begin building the collector exit pipe which was made more complicated than most 302 installations by my rear steer and tube shock set-ups. I used a combination of 90 and 45 degree bends to give enough room to clear the rack boot and shock tower. I’m not going to run any kind of cross-over so the exhaust will be going straight back under the floor boards with the mufflers (Spintech Cruisers) located just behind the rear cross member and exiting in front of the rear tire. To help dissipate heat, the floors have been lined with DEI reflective mat insulation. Unlike most sound and heat barrier material, the DEI product mounts under the car with a super aggressive adhesive. This is the second time I’ve applied it and can say, without equivocation, that it absolutely works as advertised.

Taylor 45 degree plug wires

Taylor 45 degree plug wires

One of the pieces of fallout from the new headers was that my straight plug wires would no longer work (even with protective boots) so I had to change them out for a set a more standard 45 degree bends, Taylor’s in this case. I’m not a big fan of the yellow but the reports on Taylor wires is that they’re first rate wires so yellow it is.

Autolite 410 w/manual choke

Autolite 410 w/manual choke

Another change was to go from the heat riser style coke on my Autolite 4100 carb to a manual choke so I didn’t have to drill a hole in the new headers for the heat tube. The early HiPos used a manual choke but the originals are very scarce and expensive when you can find them. Thankfully, there’s a fairly robust aftermarket for these parts and I was able to source a conversion kit for $65. The lack of instructions made it take longer to install than it should have but the result is simple and clean. Choke cable is located on the forward bulkhead to the left of the steering wheel, under the dash.

I’ll add more to this post as I get farther along in building the exhaust. Mufflers should be here in about a week so, in the meantime, I’m going to content myself with finishing the exhaust up to the muffler and fitting the right side header. So keep watching this space for updates.

Final mock-up fro header extension

Final mock-up fro header extension

Mid-pipe with clearance joint

Mid-pipe with clearance joint

Update – 9/17
I was able to complete the final mock up on the header extension as well as fabricate the mid-pipe and the clearance joint that will help keep the pipe tight to the rear crossmember. The SpinTech muffler is only 16″ long and 9″ wide. Even as small as it is, it will just fit in front of the forward leaf spring mount. Exiting to in front of the rear wheel should not present any problems (famous last words).

Tomorrow night I’m going to mark and cut out the right side wheel well opening and test fit the right header then cut up and assemble the pipes need for the header extension.

Comments

comments

Tags: , , , , , , ,