Marvel Fuel Filter Replacement – 1925-1929 All Buicks

[Hubert_25-25]

      There is a fuel filter screen on the plug on the bottom of the Marvel carburetor.  It is located below the fuel inlet.  Trash collects around the filter and the fuel travels up the center to the needle and seat.  The filter is to keep trash out of the jets.  On many Buicks, this filter is missing, as it may have been plugged and then removed to get the car started and never replaced.  

The filter is Sierra part number 18-7832 or Mercury (as in outboard) 1399-3938.   

The screen I found is the perfect diameter, but it is 1.10 inches long.  It needs to be ¾” long or just slightly less.  I slid the screen over an 11 mm socket for support.  I cut it on my band saw which has fine teeth, and I went slowly to make a nice straight cut off line.

The filter material used is very stable and the cut off edge does not require solder for stability.  If you want to solder the cut edge, heat the  solder in small metal cup, then dip the cut screen edge into the hot solder.  The original filter had an additional brass piece to hold it to the plug, but this filter fits around the diameter of the plug in the 1/8” cylindrical section above the plugs threads. I did use another socket to help flare the end slightly.  The gasket on the plug is a copper/asbestos crush gasket available from www.restorationstuff.com  New gaskets have a non asbestos filler.

     This is for all Buicks 1925 thru 1929    Hugh

Edited May 29, 2021 by Hubert_25-25 (see edit history)

[Mark Shaw]

Hugh,

    Although your effort to restore the original Marvel carb is commendable, original fuel tanks will almost always contain corrosion debris.  This potential contamination will require a good cleaning and/or be lined with an ethanol resistant coating.  The fuel line must also be cleaned and/or  replaced to eliminate carb contamination to use only the the small carb screen.  Many owners I know do not perform these tasks before getting their cars on the road.

    In any case, I still recommend using modern "see-thru" fuel filter hidden between the fuel tank and the carb to provide more filter surface area to do the job.  This is particularly important for those who have not fully restored their fuel system as described above.  The "see-thru" fuel filters are cheap and make it easy to diagnose fuel problems. 

 

Edited May 29, 2021 by Mark Shaw (see edit history)

[Morgan Wright]

On 5/29/2021 at 10:39 AM, Mark Shaw said:

Hugh,

    Although your effort to restore the original Marvel carb is commendable......... The fuel line must also be cleaned and/or  replaced to eliminate carb contamination to use only the the small carb screen. 

 

 

Don't I know it. One of the first things I did when I got my E-49 was take the fuel tank to a radiator shop and have it professionally cleaned out. I was very naive to think that was enough, turns out there is just as much rust in the fuel line as there was in the tank. The fuel line runs under the car, the fact that it's lower than the tank and engine means it's basically a gravity sump to collect rust particles. Rust has a density of 5 and gasoline is only 0.7 so the rust sinks like a rock in the tube, only to be dislodged by modern "detergent" fuel.

 

Basic 5/16 copper tube is available everywhere, and there is nothing "original" about 5/16 copper tube made 100 years ago, that you can't replace it, copper is copper, and if it's full of rust you better just replace it unless you can think of a way to scrub it out. I've been fighting this for 2 years, my carb gets full of rust until the engine gets starved for gas and I have to take the idle jet needle out the bottom of the carb and let the rust out. These are the filters I've tried but I think I'm also going to replace the copper line soon and be done with the problem once and for all.