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TR2/3/3A TR3A VS TR4 Long Tube inlet manifold


Jedi Hopeful
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Are there any advantages/disadvantages to using a TR4 long tube inlet manifold on a TR3 engine with H6 carbs or should I use the shorter TR3 inlet manifold?


Jedi Hopeful
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The long tube inlet manifold is 3/8 inch bigger than a standard TR3 inlet manifold. I suspect there's a good possibility the air cleaner would hit the inner wing. Part of why I asked the question.

Marvin Gruber

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If you use the original air filters I believe they will hit or be very close. Let use know how it works if you do it. I have a TR4 engine I plan to use in a TR3. I will be changing out the front mounting plate.


Senior Member
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I have the setup you are asking about. My 3a has the small port 4a head in it so I wanted the matching 4a intake. I use the H6 carbs that came with the car. Heres what I found:

1. Stock air filters will hit the fender well. I made a set of filters with tapered K&N filters. I offset them vertically about 1". I have about 1/4" fender clearance. Adjusting the fwd carb jet nut is a pain.
2. The stock throttle linkages binds up. My manifold is about .62" longer than the 3a manifold. I also think the mounting angle is different. I went to a cable.

The HS6 carbs would fit a lot easier. The H6 carb is 5.5" long, I think the HS6 is somewhere in the 4" range. I installed a header at the same time I swapped intakes so I did not get a direct comparison. It does run well.

Good Luck, Roy


Jedi Hopeful
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Seems like a lot of work for not much, if any, benefit. Think I'll go with the stock TR3 inlet manifold. Thanks.


Darth Vader
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I've been running a 4A manifold on my 3A for years. I mounted the round mesh and foam air filters. I had to push the bottom of the front filter in slightly for clearance. I didn't notice any fouling on the throttle linkage but I'd be interested in seeing a picture of the cable set up. I believe the 4A intake would be advantageous for better engine breathing.

Simon TR4a

Jedi Knight
Kastner says the 4a inlet manifold flows significantly better, but how much improvement you would get on a stock engine I do not know.

Don Elliott

Obi Wan
For a late TR3A I restored where the owner had a long TR4 intake manifold, I had to use very thin air filters but they are not fully circular. There is a flat that I adjusted so the filters fit on. But the owner felt that the engine was not getting enough air flow through the thinner filters hence lower output power.

I also saw a photo where someone had taken a 5 pound hammer and bashed his inner fender about 2 inches so that the common air filters would fit without hitting to inner fender.
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