View Full Version : TR4/4A Fitting TWM manifolds for DCOEs

06-11-2018, 09:30 AM
I read the about all the troubles people have had getting the TWM intake manifolds to fit without interfering with the exhaust. So bad that a couple of good tech returned them. Well I read all that after I purchased a kit a while back so I'm in with both feet.

Now, I'm almost done but it's been fun!.

First, I planned to use the Moss two piece exhaust header that I bought a decade or so ago and never fitted it. It's all JetHot coated too. Beautiful. The problem I discovered is that the flanges on #1 and #4 are welded out of line with one another, not parallel surfaces. #4 was welded on about 1.5degrees off. How did that ever happen when I expect that these are jig welded? I haven't called Moss yet, it's been a decade since I purchased it. New one is beaucoup dollars that I don't want to spend again. btw - this might have fit with only a little cleanup at the interfaces between the intake and exhaust manifolds if it was welded correctly. Slight interference around the flanges.

So my altered plan is to use an original 4A iron header.

To fit the fat tubes of the TWM manifolds (designed fat to prevent the cracking that Cannon manifolds sometime develop due to the weight of the carbs hanging off; racers sometimes build up the flanges on Cannons to avoid this), so to fit the fat tubes, it required 1) that the mounting pieces that slide over the studs to clamp the assembly to the head needed the hole drill out slightly off center to allow them to slide along the studs 2) and the reliefs ground into the manifold to accommodate the studs be widened and lengthened a bit to prevent the nuts from binding against the manifold.

I did this using for 1) a brad point drill bit in my press. Since I wanted to drill off center, I couldn't use a normal tipped bit because it would walk back into the original hole. I use the cutting edges of the brad point bit and a drill vise to hold the manifold clamps securely. Iron is soft and it cut OK enough so that the clamps now fit without binding. 2) I first marked out the area with a sharpie, then used a conical burr bit to remove most material then a conical sanding cone to smooth the area out. Fit and recut several times, each time checking the manifold for sign of binding.

I know I'll have to post some photos.

The manifolds slide on, the clamps slide on with them, and I turn the nuts as I install the manifolds. No done yet. Next I removed the trial fit TWMs and bolted the exhaust on using the two side studs only. I then fit each TWM manifold individually, marking and adjusting as required.

As expected I needed to trim the interface between the exhaust and TWMs a bit. A little marked grinding, then sanding smooth was all it needed but...
As another member noted in a prior post, the fat tubes interfered with exhaust tube #2 and #3. I used a flashlight to shine up through the interference and turns out, it was mainly from the rough casting of the exhaust sticking out and hitting the TWMs. Exhaust is coated ready to go, coated so I ground down the manifolds where they were gouged by the casting bumps. So, so far so good.

Seems like a lot but all this is very minor. After my mods, I put the manifolds in my blasting cabinet to even out the ground areas with the casting. Came out nice.

What else I learned is that these are a PITA to install. I slid the manifold and clamps on together, then held it off far enough to get the nuts started and rock it back and forth alternating between the nuts. The inside nuts have more room so the outside nuts #1 and #4 can be fingered on a couple of flats at a time. No rooms for lock washers on the outside upper nuts, just the inside and lower exhaust, and lower center clamps.

Not quite done but almost and hopeful that it will all work.

So do I call Moss about the header? Been a long time but it is their faulty welding.

06-11-2018, 05:54 PM
Hope you like these. Still a little more to do 54090540915409254093

06-12-2018, 03:23 PM
Hey Peter.
This is interesting
Course I'm an EFI guy