Fitting filtered air box to MA-4-5 Carb

Frank Smidler · #1 12-01-2007, 10:56 PM

I have found so much great info in the archives at VAF that it suprises me when I have an issue that haven't been addressed yet. Well here is one I did not find.

I am ready to fit the filtered air box to the carb. The carb is a new MA-4-5 from Van's in 1999. I understand that I have to cut a hole for clearing the rear drain but I have additional interference along the rear edge of the mounting face due to a lip that goes across the full width. If I were to notch the top plate of the air box for this lip it would be so close to the bolts in the rear that I fear it will easily crack. On one side it looks like I can file the lip down. On the other side I can file the lip down a little to the body but it will not be flush with the mounting face for the air box.

The Questions I have are:

1. Have others had this issue? How did you handle this?
2. Is it OK to file off the lip on the carb?
3. Is there a gasket that should be used between the carb and the air box top plate that can take up offset at the rear?
4. Has anyone used a spacer allow clearance over the lip at the rear?

Thanks for your help.

Ironflight · #2 12-01-2007, 11:47 PM

Hi Frank - your post made me think way back, and yes, I believe that I DID make a spacer - and the only place I would have put it would have between the FAB and the carb - I bet it was to clear that lip. I don't KNOW if you can or can't file the lip off the carb body, but it would make me awful nervous to modify an expensive part like that - better an aluminum spacer from some scrap material!

Paul

robertahegy · #3 12-02-2007, 06:52 AM

I just went back and read the instructions and they state:

Most MA4-5 carbs for the 0-360 have a flashing area on the bottom at each side of the drain plug boss. You can either file this area flush (plug the ports in the carb to keep it clean) or make a spacer the same thickness as the flashing that will allow the VA-131-C to lie flat on the carburetor bottom.

Hope this helps,

Roberta

grover · #4 12-02-2007, 07:23 PM

I have no fear (and not much smarts) so I filed it off. . . very carefully.

zilik · #5 12-02-2007, 09:42 PM

Yup, a gasket goes there, a thick one if needed. A spacer also works.

Frank Smidler · #6 12-02-2007, 10:37 PM

Thanks for everyones help. Roberta, thanks for indulging me and quoting from the FAB instructions about the flashing. Since mine is a 13+ year old project some of the older instructions do not have as much info in them as the newer ones, in this case mine did not have that information.

What I did was file the flashing off on both sides of the MA-4-5 carb sump. On one side I could file it down to the face but on the other I filed it down to the body which was 0.040 higher than the intake face of the carb. I did not file the body itself only the obvious flashing that had no structural or functional purpose.

I have seen pictures on the web were some builders notched out a wide slot to clear the flashing and the part of the body that was higher than the mounting surface. This resulted in very little material around the bolt holes and may have been the cause of cracking of the top plate around the bolt holes. Therefore I did not want to make this notch. With the flashing filed way I only needed a 0.060 inch spacer resulting in a sump cutout similar to the sketch provided in the instructions provided by Van's.

I took some photos.

http://picasaweb.google.com/FSmidler...FilteredAirBox