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TR6 TR6- Weber 3236 downdraft conversion

Mikie808

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I recently got tired of fiddling with my Strombergs and wanted to try the progressive Weber downdraft carburetor setup on my TR6. It was sold as a kit with spoon-shaped manifold extensions to make the downdraft carb fit on a side-draft engine. I was skeptical of the idea but the price was very attractive. A few notes:

1. They fit, but not well. The carburetors sit backwards in my opinion, with the primaries being furthest away from the intake. Air flow needs to go all the way past the secondaries in order to get to the engine. They should be turned the other way around, because the primaries get used most and the secondaries only open when you floor it. Also, it is difficult to get to all the necessary fastening points, and I had to dent the inside of the wheel well in order to make clearance for a vacuum port sticking out on one carb.
2. They run the motor really nice. I had to change the stock main jets from 140 to 150 to get the mixture right- probably because I shaved 1/8" off the head a couple years ago. It was acting lean at first. But now it is running smoother than ever before and has more power. Gas mileage went down a few points, however.
3. You need to hook up the hot water port. I didn't do it because I thought it was an option for cold-weather climates and I live on a tropical island. Wrong. When I run at-speed, the carbs get so cold they condensate and sometimes this leaves water in those cute little spoon manifold extensions after I shut down. It makes for fun starting, the next time.

All-in, if I had to do it again, I would probably look for a side-draft setup. I love Webers and am not sorry with where I ended-up, but it took some gymnastics to get here.

Mahalo, MH
 

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mctriumph

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IMHO, the Tr6 should have been a tri-carb car from day one. It is impractical to feed six
cylinders with 2 carbs, and a waste of power.Unequal length intake runners is NUTS. The factory
manifold is to say the least "a poor design".Any carb that you put on this, is just lipstick on a pig!
Mad dog
 
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Mikie808

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IMHO, the Tr6 should have been a tri-carb car from day one. It is impractical to feed six
cylinders with 2 carbs, and a waste of power.Unequal length intake runners is NUTS. The factory
manifold is to say the least "a poor design".Any carb that you put on this, is just lipstick on a pig!
Mad dog
I agree that 3 is better- if I had a larger budget, I would have gone with 3 Weber 40 side-drafts and a fast road cam while I was in there. When I rebuilt the motor, I kept future modifications in-mind…
 

mctriumph

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In my experience three 175 in carbs is plenty.My 6 got 3 Strombergs, ran like a song.
If one was completely mad, 3 two inch Jag SU's could have fed a radical motor and looked
amazing!
I cut apart 2 stock air cleaners and welded them into a tri-carb cleaner used a 240Z element.
It looked stock & as the factory would have done on a "special" had they built one.
Mad dog
 

JHaydon

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Not sure why the secondary is closer to the engine, but that's how we do it on Formula Ford as well -- which is a little weird considering that Ford OEM used the "mirror image" 32/36 DFV model. The old old old Weber books show illustrations of inline engines fed by progressive carbs with the primary closer to the engine. The main consideration is to have the float bowl pointing towards the front of the car.

Could be they wanted to keep the throttle cable/linkage on the more accessible side of the carb.
 
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Mikie808

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Not sure why the secondary is closer to the engine, but that's how we do it on Formula Ford as well -- which is a little weird considering that Ford OEM used the "mirror image" 32/36 DFV model. The old old old Weber books show illustrations of inline engines fed by progressive carbs with the primary closer to the engine. The main consideration is to have the float bowl pointing towards the front of the car.

Could be they wanted to keep the throttle cable/linkage on the more accessible side of the carb.
It’s interesting that the Formula Ford does it that way too. The only thing preventing me from installing these the other way around is the shape of the manifold extension- it’s just a little too close. But, if “the spoon” was any longer, you would have to cut the inside of the wheel well to make it fit. There’s just not enough space. I would give this kit a “B” for fit and an “A-“ for function. I’m mostly happy with it.
 
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