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  Megasquirt -
        Building a Custom Triumph GT6 Injection Manifold

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 Building a custom GT6 F.I. manifold

The other half of the story

Special Update Whitey finally gets it's 6 cylinder engine,
          Fuel injected at that!  

Section #2 - Whitey's Spit6 conversion Process         F.I. Home Page
 Introduction   First Models  Sensors  Engine Management Basics
 Requirements  Sub-systems    Tuning  Sizing Injectors
 gas tank mods   Fuel supply system   My first ECU   F.I. Links - Sources
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Other peoples Triumph F.I. Installations/Projects
Special Project   Megasquirt - The Quintessential D-I-Y Fuel Injection ECU
 Building a Custom GT6 Manifold   Whitey's F.I'ed Spit6 Project
Building an MGB manifold Experimental twin bodies on a GT6
 Building a twin TB MGB manifold The other half of the story 
     Obviously these don't exist, off the shelf, so I had to design and build one myself. I decided on many parameters of the design, the way I always do, based on the parts I could find and what I could tool up myself. 

These are the main metal parts after polishing (and my throttle body)

     I used flanges cut from an old manifold. Plain and simple... it was easier than trying to make them from scratch myself. I bolted them to a spare head and port matched them by grinding them to match the head ports perfectly.  I used a 10" composite cut-off wheel mounted in my miter saw, to cut the port pipes. This is all 6061-T6 and should be easy to weld up. I even found the proper 4043 welding wire for my new wire spool welding gun.  I figure polishing the metal now (as shown in the pics) was easier than trying to do it later. I'll only need to re-polish the areas around the weld later on after assembly.
     I've angle cut the runner pipes as pictured to help standardize the air path lengths between the cylinders as much as possible. The gap left in the middle will make it easier to add the crankcase breather pipe in line with the normal rocker cover vent pipe. The angle is also to allow me to mount the larger 3" id. tube will sit about 1.5-2.5" below the center line of the head ports for greater bonnet clearance.  The throttle body back plate was purchased from a guy custom making them and selling them on EBay. I called him and had him make me up one to fit the 65mm throttle body I'll be using. The polished IAC valve was purchased off EBay, as well as the throttle body, which as purchased did not have one mounted. 

65mm Ford Mustang throttle body with custom plate and polished idle air control valve

     My fuel rail is being made out of parts from a BMW M3 fuel rail. I cut the little injector cups off a rail and will weld them onto a rail of my design. A separate firewall mounted fuel pressure regulator and pressure gauge will be used.

regulator, manifold bungs, pressure gauge and adapter and rail bungs


update 2/18/06

  The Toyota fuel pressure regulator is adjustable (30-100 psi). The Marshall  glycerin filled fuel pressure gauge will be mounted right on the rail. I've got two different styles of injector bungs ready to weld into the manifold.  I had milled an extra groove in the larger bungs (bottom center) around the tops to capture a second larger o-ring. This would have helped to isolate the injector and minimize heat transfer/soak. But I think now I'll probably use the thinner style (bottom center left) due to the smaller mass... expecting less heat transfer to begin with, as well as a cleaner look. 

    I haven't decide which pump to use yet. Either the Volvo unit above, or the MSD unit below. The MSD unit does match the port size of my fuel pressure regulator unit better. Plus the simple hose barb ends of the MSD unit should make for an easier installation and repair process at any future date.

     .  I've never really ever tried to build something out of metal this complex before. I'm surprising myself even, how well this seems to be turning out thus far. Since I hate measuring things, it takes me a bit of thinking to figure out the right sequence and or how to jury rig stuff to do what I want to do. This sequence of manufacture and assembly has been tricky. I built up a jig for the head to sit on. I bolted the flanges to the head and setup a rack to hold the runner tubes while I welded them to the flanges. I must have then spent about 8 hours, just grinding and re-polishing everything.  I then built up this jig to drill the injector bungs. I wanted to make sure they'd all be in line so everything was bolted back to the head, and moved to the drill press. 

Welded runners/flange assemblies, bolted to spare head 
and jigged to drill bungs

 Cutting up the metal isn't all that hard, but welding aluminum can be really trying. These now really look great, but it took a LOT of grinding and re-polishing to get them this sleek looking after welding.   

bung/injector test fitting

bung/injector test fitting

      Another big advantage of angling these runners down a bit, allowed me to position the injectors to fire right down at the backs of the  valves.  In this next shot you're looking right down the drilled bung hole as if YOU are the injector. That's the back (inside) side of the vale seat you're looking at.

     Next comes welding all the injector bungs in. I'll need to build another jig to hold them and line them all up in relation to each other. Once positions are determined I'll need to cut/trim all the bungs at an angle, to minimize the grinding on the inside of the runners.

update 2/21/06

Well I got the bungs installed and all the runners cuts to the same lengths. In this next shot you can see the jig I made up to make sure all the bungs were level to each other so the fuel rail and injectors would all be equidistant.

     It's simply angle iron with bolts through it and short pieces of 1/4" fuel line. The bungs were all jammed onto the hose bits, inserted into the runner holes, and tack welded. After a lot of grinding and polishing, I'm happy with this end of the manifold.


...update 2/23/06
     Well I cheated  bit here. I drilled the main plenum runner holes on my own bench top drill press, but only to a diameter of 1.5"  (it's the largest bi-metal hole saw I had). I needed to go out to 1.65" for the runner pipes to enter. But doing all that grinding was/is getting tedious. So I took it into work, and had my buddy in the machine shop, bore them to 1.65" and accurately space the holes, based on the template dimensions I gave him. It took us all of about ten minutes to re-drill the bigger holes. He was quite impressed with my 'eye-balling' and 'hand held' holes I had already drilled.

     So last night and tonight, I finally completed the final shaping of the plenum tube holes to get all the runners to fit right.  BUT...at the last minute I decided to extend the plenum a couple of inched to increase it's volume, as well as move the throttle body out a few inches from the front runner. So a bit more work was required. I finally got it all welded up, and spent about two hours just grinding all the welds to look this sleek.

all welded up, the welds ground smooth, and still needing to be polished 
once again. Here I'm just test fitting everything


top view - Her you can see that I've extended the main plenum's length. Also note the 
extensive shaping of all the metal transitions. It almost looks like a cast peice doesn't it?!


     In these shots, the manifold still needs to be re-polished once again. Tangs need to be added to fasten the fuel rail mounts to, and a throttle cable linkage and mount designed and mounted.

update 2/5/06  The manifold is complete!  see it here


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