HEADER: Custom designed and fabricated, 4 into 1 style, with 1 5/8 in. OD tubes, 36 in. long primaries (from valve pocket to inlet of collector), 5 in. long collector, and 2 ¼ in. OD tailpipe. (2010)
ROUTING: Tubes are routed through the inner fender panel. The stock exhaust is routed through a hole in the chassis.
TWO PART DESIGN: For ease of installation and removal, the header is comprised of two parts that bolt together with custom joining flanges and a gasket.
COMPONENTS: The head flange, tubing and collector were purchased from STAHL Headers.
TAILPIPE: Two 2 ¼ in. OD tailpipes were constructed and are interchangeable. One is a straight pipe and the other has a muffler welded in it. Both exit ahead of the rear wheel. The muffler is SUMMIT, PN HED-25010. A Flexible Stainless Steel Joint is between the collector and tailpipe, SUMMIT PN SUM-652210.
BUNGS (for O2 sensors): Two bungs are welded on the header, on the #1 and #4 pipes, SUMMIT PN INN-3764.
DESIGN: The 1 5/8 OD and 36 in. long primaries were based upon two sources: the Dyno sheets from Greg Solow that were in Kastner’s “Historical and Technical Guide for Triumph Cars”, pp. 30-32, and simulation runs using the Dynomation Advanced Engine Simulation, which showed more HP at 6000 rpm than with 34 in. or 38 in. primaries.
The Head Flange from STAHL needed some adjusting: three holes for the attaching studs were extended to match the stud locations, and material was removed from the bottom for block clearance due to milling the head.
Joining Flanges of 3/16 in. plate were fabricated to bolt the two header pieces together. Each flange has four 1 5/8 in. holes for the tubes and eight ¼ in. holes for allen bolts.
A Jig was designed and built to hold the head flange and one joining flange while fitting and welding their tubes in place, and also to hold the other joining flange and collector while fitting and welding their tubes. The Jig is available.
TIG welding was used to attach the tubes to the inside of the head flange, and then the tubes were brazed to the outside of the flange.
BUNGS for the O2 sensors were machined so only the smaller diameter portion of the O2 probe fits into the header tube, and the ends of their plugs were shaped so they were flush with the inside of the tube.
THE HOLE in the fender panel was carefully cut with rounded corners and reinforced with an annular Doubler around the hole.
The GASKET SURFACE of the head flange was ground at Cylinder Head and Motor Supply in Minneapolis.
The MANIFOLD GASKET is REMFLEX PN RF20-001, and the gasket between the joining flanges was cut from a blank of REMFLEX material, PN GS16511.
SIDE NOTE: THE PREVIOUS HEADER.
I built an exhaust header in 1967, which was a 4-2-1 design. Prior to that, the stock TR3 exhaust manifold was used. The design was adapted from a magazine article (which has been lost) which had a sketch and comments, and I think was used in one of the MG top speed record cars. Following measurements from the TR3 head, a pair of head flanges were milled out of ½ in. thick mild steel. (The second one was eventually used in fabricating the header for the PEYOTE in 1983). It was a two piece design with the collector outside of the frame. They were bolted together with custom flanges, and routed through the hole in the frame for the stock exhaust, which was slightly enlarged for two, side by side tubes.
That manifold was modified many times over the years, to accommodate the long style intake manifold (1996), and to avoid the forward supports to the front suspension (2004). For the final few years it was wrapped in “header wrap” even though I was warned against this. Eventually, a section of the header was blown out during practice at an SVRA event at Road America in 2009. I then began to contemplate the new 4 – 1 header, and decided not to use header wrap!
Note: a “field repair” was done on the blown out section by forming a piece of aluminum around the tube, gobbing the edges with JBWELD, and applying hose clamps. Morgan was able to run and finish the feature event, as the JBWELD melted away.