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TR4/4A DCOE air filters


The engine is not even put together yet and I'm thinking about air filters. So here's the cart (before the horse) questions.

1) Which is the thickest air filter for DCOEs than can fit without inner fender mods on a TR4A?Will 2-1/2" clear?

2) and which will fit over the ram pipes and still provide ample filtering?

My preference is not foam but a K&N type filter media, but most say w/o ram pipes.



Jedi Knight
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This was what I used when I was running Webers.


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Jedi Trainee
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Normally I'm not a big fan of foam filters but the ITG filter is nice set up. As for the K&N air filters, I'm not sure what thickness can be run on TR4/4A from a body clearance standpoint. I do know that on a TR250/5/6, that the 2 1/2" is too thick unless you want to start altering body work.

First question is which DCOEs (40 or 45) do you plan on running? If it is the 40s, then use the filter for the 45s. The opening for the stacks on the K&N 40DCOE backplate is too small for any sort of stack. If you run the 45 DCOE filter on a 40DCOE you do not have to open up the hole in the backplate. For the 45s, the 48DCOE filter probably offers up clearance for the stack or at the very least reduces the amount of material you need to remove to fit the stack.

APT offers a 16mm stack for both 40 and 45DCOEs which work with the short K&N filters needed for the TR250/5/6 applications:

https://aptfast.com/ShowItem/102460 16mm Tall Weber 40mm DCOE Ram Stack.aspx

https://aptfast.com/ShowItem/102463 16mm Tall DCOE 45 Weber Ram Stack.aspx

You might want to contact them and see what they have to say about K&N filters for DCOE use on the TR4/4A.


Luke Skywalker
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Two points here. First, you MUST use velocity stacks with side draught Webbers. Second, do not use foam filters, as petrol will be spit on them from the carbs. If you happen to have a back fire and do not know, the car will ignite.....not good.
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