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MG MGB Technical - SU Carb Conversion

Converting carbs to SU, hitting usual problem re airfilters colliding with brake master cylinder.

Am using an air filter box off a Triumph Spitfire 1500, and wonder if this will allow sufficient airflow into the twin HS4's.

This box has twin inlets 1 3/8" to which a pair of pipes/tubes are attached.

I am proposing to run two pipes/tubes from this box into a pair of K&N pancake filters for which a special bracket has been made.

Question is will I get enough air thru the K&N's into the air box and hence into the carbs.

Ask this question because the air box inlets are slightly less than 1 1/2"

View the air box about two thirds down this link under the 1500 engine size.

http://www.rimmerbros.co.uk/cgi-bin/rimmer?spitfire/fuel
Jack

That cold air box was designed for a pair of HS4s, so I would think it should work. If you really want to make sure you can file a little off from the inside to reduce any flange there might be.

The cold air box you are purchasing is, I believe, designed to be fitted with the filters inside it, and the pipes running to the front of the radiator, to gulp in the cold air.

Assuming you have the box in hand and it fits the manifold, I would say the best thing would be to put the K&Ns inside the box, as then they will be out of the way of any road gunk that will be thrown at them if they were fitted at the front of the car.

Dave

Jack:

If you are located in Syracuse, NY take a look at Victoria British Ltd. I don't know if you're looking at the same K&N filters I am but Victoria has them for $22.95 each and it looks like Rimmer is getting $65 for the pair.
Jack

Jack; Have you verified that the dimensions between the MGB filter mounting holes are the same as the mounting dimensions on the Spitfire air box? Assuming they do fit I suspect the air inlets may be too restrictive for the MGB engine. The Spitfire filters are also very small compared to MGB filters. You can mount filters direct to each carb and not use the air box. No need to buy K & N filters to use in the air box, you will not have any change in performance due to the air box restriction. FWIW, Clifton
Clifton Gordon

The two holes in the airbox which butt up to the carbs are 1 1/2", so there is no problem there.

However, as you can see from the Rimmer webpage, this airbox has two entry pipes, and it is these which are my concern, because they are just less than 1 1/2".

The K&N pancakes I have obtained, are now slightly modified, insofar as I have had a 3" piece of tube welded to each of the holes which would normally butt up to the carbs.

This is to allow flexible hoses, such as those shown on the Rimmer page, to connect the two pancakes to the air box.

As you can see, a lot of work has gone into this, only for someone at the last minute to point out the air starvation problem. Horror of horrors.

The question I am seeking to answer is will this setup starve the carbs of air, given that the twin inlets to the airbox are 1 3/8".

This question arises having read earlier posts on the subject of using K&N conicals, which seemed to suggest they would starve the engine of air.
Jack

With the flexible hoses mounted to suck air from the front of the radiator there wouldn't be a problem as the air is colder and denser there, combined with the slight ram air effect. If you are using the airbox to suck air in from inside the engine bay, I guess there might be some problems, as the air will be warmer and less dense.
dave

This thread was discussed between 29/10/2004 and 30/10/2004

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