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MG MGB Technical - Best air filters for carb conversion?

What are the opinions on the best air filter for a 1977 MGB that is being converted to dual SU's? I plan to install two HIF4's with MGB manifold and exhaust, and realize there will be minimal room between the carbs and brake booster.
And, is there a preferred heater pipe for this same conversion?
Thanks in advance,
Randy Olson
1977 MGB
randy olson

Randy,

With twin HIF4s I recommend a pair of K&Ns. If you don't have the stock air cleaners, I recommend you can build a pair of "Bob Filters" which I recently did with a pair of door knob wall protectors available at the Home Depot for less than $3 each. Painted, they look good, but its the filter that really shows and breathes allows your carbs to breathe easily.
Joe

Randy,
Been there, done that!! The best fit are the Moss repro Snelling and Helling filters. Very thin, chrome topped filters...and even they will be close to the brake booster. I've recently switched to the K&N cone shaped filter, which also has the offset base. It too is VERY close to the brake booster, but affords much better breathing ability. AND...look COOL!!!
Pete
Pete C

If you check the archives, I describe an air box that provides a much better breathing alternative to the conical filters. I don't have a digital camera (I don't know why I don't just go out and purchase one but I wouldn't tend to use it all that often), however I have taken some pictures and am waiting for my wife to take them in for processing to CD. When that happens, I'll be able to provide photos of the installation upon request.

For "off the shelf" solutions (for late model B's where you need to clear the brake servo/booster and MC), the conical filters are probably the "best". However, they are not a very good breathing solution, in that they do not allow for the use of stub stacks and the rear filter has very little clearance. On the other hand, if you're shopping the catalogs, they're about as good as it gets (short of reverting to non-servo assisted brakes and using a better filter setup).

Barry

P.S. Pete C., it's good to see other postings from the local area. Maybe I'll see you out on the road sometime.
Barry Kindig

I'm interested in seeing pictures of Barry's air box. Right now I only have the catalog options at my disposal. The conical K&N seems like the consensus favorite...right? But if there are better options out there I would like to know about them.
Octagonally,
Randy Olson
1977 mgb
randy olson

I'm also interested in seeing pictures of Barry's air box.

In the short term, would it be possible for Barry to describe his idea, starting with where we can check the archives for his idea.

Year and subject heading, for example.
Alex

I went looking in the archives and these posts are hard to find. One of them is titled "The Great Experiment is Finally Completed", however, you really have to dig through all of the text (as it covers a much broader topic) to obtain the info. So, let me try this:

Imagine a 3" deep X 6" diameter K&N filter at the front end of the air box, extending toward the radiator surround. It attaches to a very nicely radiused opening at the front of the box (with a gasket to ensure a good seal, of course). The box itself, smoothly tapers toward the back to clear the servo/master cylinder found on the later North American RBBs. The box itself is actually held onto the (HIF4) carbs using the original style stub stacks. I use the original type air cleaner gaskets to the carbs. The box then has an aluminum cover with a gasket that has a nice press fit (sort of like the lid on a can), which is held in place with a screw in the back. There's a lip this cover inserts into at the front end...the screw holds it against this lip and the gasket seals the box closed (so the only opening is via the filter). The box is not particularly large, as it can't be to clear the booster. The front is wider, with a taper leaving about 1/4" to 1/2" of clearance at the MC (tight, allowing the maximum area, while still providing enough clearance to prevent fouling). The box is painted black, the cover is polished aluminum (with the filter attached, it looks very nice, as you'll see when the photos become available). Since everythings a bit close, it takes a bit of patience to install but I've come up with a pretty good working method (ratcheting wrench...makes it pretty easy). All air entering the box or the carbs is smoothed out through a smooth radius opening (stub stacks in the case of the carbs).

This box was not my design or idea but rather Mike Brown's. My description probably doesn't do it justice, so the pictures will be needed for you to fully appreciate the work that went into it.

Hope this helps,

Barry

Barry Kindig

Barry, the box idea sounds good...you'll need to do working drawings with a fold out showing the shapes of sheetmetal to cut! I look forward to the pictures. I did find quite a few references in the archives to various options for the filters. One of interest involve using a Volvo air plenum. I need more information about all the successful set-ups out there (and there must be lots of them), so let's hear it from those who have done it and are happy with the results.
Regards,
Randy
1977 MGB
randy olson

Randy and others,

I'll post pictures, when I get the chance. However, this is not my personal design. Therefore, while one could probably figure out how to build one (by careful measurement, along with some trial and error), precise measurements are not mine to give away. Mike Brown (who posts here occasionally, typically providing his email address) created this unit...something I've been careful to point out over the past several related postings. I'm not trying to "tease" other posters/BBS members with this unit, rather I'm interested in pointing out the existence of other possibilities. Hopefully, I've given those interested sufficient information to pursue this further, if desired, without compromising any trust relationships.

Barry
Barry Kindig

Randy, I have a 79B and I converted to dual HIF4s. I wanted to try something different so I just made my own system out of two 13.5" EQUAL* length 1.400" id pieces of mandrel bent mild steel tubing, two flanges, one 3.5" round collector and a single K&N cone filter. The rear tube is welded to the flange, takes a 90 degree bend to clear the booster, pointing toward the radiator. The front tube is again welded to the flange and makes a tight u-shaped bend, clearing the top of the master cylinder, and just ahead of the front of the brake reservoir. Both tubes are welded into the 3.5" mild steel collector (about 3.5" long). The K & N single cone filter looks just like the ones you see on all the modded japanese cars... it just slips on the collector and you tight the hose clamp.

*Out of convenience, I tried unequal length tubes but it didn't work worth a darn under 3000 rpm (had to cut it apart and start all over). This set up seems to give me great low end and high end. By the way... it looks very trick... lots of work but it looks very trick.
Scott

Pardon my ignorance Scott, but what is a 3.5" round collector, and what is the part number for the single K&N cone filter.

Alex

A collector is just a junction point for two or more pipes to come together in a single outlet. That term is frequently used in building exhaust headers, where the individual pipes from each cylinder join. The standard B exhaust does this as well, with two pipes coming to one.
Hooks

I also would like to know the part number for the cone shaped K&N filters the work with the SU carb conversion on a rubber bumper B.
Randy Olson
1977 MGB
randy olson

I note Hooks comments re a 3.5" round collector,and now understand what's involved, however is this something which has to be fabricated for the conversion, or are we going to be able to use a standard part, albeit designed for some other purpose.

Also, we still need the part number for the single K&N cone filter.
Alex

This thread was discussed between 26/05/2002 and 06/06/2002

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