Upgrading a Cub Fuel System

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Upgrading a Cub Fuel System

Postby Rudi » Sun Nov 08, 2009 4:35 pm

I have been wanting to replace my rubber fuel line with a steel one for a very long time, yet kept putting it off because I lacked the skills to Helicoil the fuel inlet orifice in my existing carburetors. Still haven't tried to do that yet, but ... I now have the proper tools (thanks Rick :!: :{_}: :D ), and I may actually do the next carb myself. However, I was fortunate in that one of my acquisitions included another carb or two which ended up residing at Cecil's for a while :roll: :lol: . Whilst visiting NY, my carbs and Cecil had a relationship of sorts -- they sat there patiently.. and then Cecil rebuilt em including Helicoils in the Fuel Inlet Orifice. :{_}: :{_}:

With no more excuses available, I decided after making Gord's fuel lines for the Super A and the H, that I really needed to do my own. So I embarked on the long awaited Fuel System Rebuild Project. One of the things that I really liked was Gary Boutwell's two primary Fuel System Upgrades... How To Install A Fuel Tank Strainer and How To Install an In-Line Filter in 5/16" Steel Gas Line. The last one came in very handy when I discovered to my chagrin that for some reason, I do not have any extra Fuel Inlet Filter Screens. Gary's project solved that problem. Yes, I am still going to try to find extra Fuel Inlet Filter Screens and retro-fit Ellie's carb with it, but for now this should do the trick.

What follows is my attempt at trying to ensure Ellie will no longer run the risk of becoming a Krispy Kub and to ensure that I will have none or at least next to no fuel issues due to dirt/crud/buildup etc., for a long time to come.

The first part of the project was to get the Fuel Sediment Bowl Assembly ready to accept the Model A Fuel Tank Strainer. I have a number of Fuel Sediment Bowl Assemblies, and I got a real surprise when I started this. Seems that in my pile of 6 assemblies, that there are at least 3 different orifice sizes in the Fuel Sediment Bowl Inlet :!: :shock: :? as well as 3 different and distinct styles. So I decided I would start practicing with the oldest and move up the ladder. (my notes are still in the shop, so I will add the side wall dimensions and other ones later).


This is one of the oldest that I have, so it became guinea pig number 1. To install the Fuel Tank Strainer as mentioned in Gary's article.. the Fuel Sediment Bowl Inlet must be bored out to accommodate the new filter.


Gary's process includes boring the inlet orifice and also trimming the smaller diameter tip of the filter. Since I have no way of neatly and accurately doing this, I needed to figure out how to mount it properly without trimming. The Fuel Strainer base largest diameter is barely 3/8", and is approximately 0.4331" in length which is the same measurement for the smaller diameter section of the base. Obviously I needed to be able to seat at least half of the larger diameter into the Fuel Sediment Bowl Inlet Tower. I forgot to measure the Tower walls and the diameter of the actual orifice :oops:.

From my observations, the smaller diameter base section would fit nicely inside the tower without restricting fuel flow, so I determined that I would have to drill a 3/8" hole approximately 5.5mm or 0.2165" in depth in the Tower itself to accommodate the filter.

I used my drill press and drilled a test hole in the oldest unit. I was very pleased to discover that it fit nicely -- actually pretty snug which is good.


So I then proceeded to move on to the next Fuel Sediment Bowl Assembly.


The thickness of this tower wall is greater than the preceding unit and measured 0.194" and 0.112" after drilling. You can also see that this particular unit is different than the preceding unit - probably a newer model. The bail tips are enclosed whereas in the preceding unit, they are open.


This is a very snug fit and to remove this screen would require using a pair of pliers. I did not think it was that snug since I just inserted it finger tight. Trying to remove it though, it became quickly apparent that it wasn't gonna happen. A little bit of penetrating oil may allow it to be taken apart during test fitting though. Will experiment with that on Granny's Fuel Sediment Bowl and see.


The next step was to install the original plug to the inlet side of the fuel sediment bowl and a 120-AA 1/8 FPT x 1/8 MPT bushing. This was required as the thread size did not accept the 1/2"-20NF fitting on the 5/16" steel brake line. This is one of the differences between earlier Fuel Sediment Bowl Assemblies and the newer version 61782C91 Fuel Sediment Bowl Assembly


Next a 122-AA 1/8" MPT Hex Nipple is needed to mate the BV2103-A 1/8 Female Pipe Ball Valve. A second 148-5A 5/16 Tube x 1/8 Male Pipe adapter is inserted in the other end. This adapter accepts the Inverted Flare Fitting end of the 5/16" Steel Brake Line so do not cut off that inverted flare :oops: cause you will have to redo that and no you cannot ask why :big shy:


The next step is to install the Fuel Sediment Bowl Assembly with the addition of the Fuel Inlet Strainer into the tank. I used pipe tape on the threads as it was the easiest for me. Loctite Thread Sealant could have been used as well. Probably will be on the next unit as a comparison. Oh just a note - each fitting gets Teflon Pipe Tape - held one thread back from the tips and is used on the final install. Also, the ball valve cannot be installed prior to installing the Fuel Sediment Bowl Assembly for clearance reasons, so wrap the male thread on the Hex Nipple and install the Ball Valve after the Bowl Assembly is installed.

Remember when I had Ellie's tank sealed with Red Kote back in 2003 :?: Looks pretty good huh :?:


Install the Ball Valve


Next lay out the length of the first section to be bent for the 5/16" steel brake line. I happened to have a few left over bits which helped figure things out.


Take a page from George Willer's Play Book, use different size pulleys as bending jigs so as to not kink the brake line. This one is a pulley from a Cub-22 Mower. I used different pulleys in this project.


Ends are a little difficult to bend :roll:


Install the finished line from the Fuel Sediment Bowl Assembly to the IH Updraft Carb.

Even though I tried to ensure good bends, after a boo-boo or two, I was down to my last section of brake line and I inadvertently got a slight kink in one bend. I tried it out, and it did not seem to affect flow, so it stays for now. A good reminder on patience and watching the bends.


Ensure that you have sufficient clearance between the gas line and the hydraulic tubes as well as the manifold and other obstructions. It may take some experimenting but the brake line is pretty resilient and will take a fair amount of bending before exceeding it's limits. If you kink the line badly or a small hairline appears.. toss it away and start over. Do not take chances as a leak in the line could result in a Krispy Kub which we all want to avoid.


The next step is to follow Gary's How To Install an In-Line Filter in 5/16" Steel Gas Line. I was lucky and I have the necessary tools to do this, but you do have to take care. I split the plastic covering on the band-saw and removed the sintered filter. Using my grinder I removed half of the upper band.


Then on the disc sander, I removed approximately 1/2 of the exposed fuel line leaving about 1/8" beyond the compression fitting.


Test fitted the shortened sintered filter


Seems to fit nicely :D


All back together.


The Fuel Filter Screen from Snyder's was about $4.00, the In-Line Fuel Filter from NAPA was about $3.00 and the brake line was less than $5.00. Add in about $14.00 for the Ball Valve and other fittings, and I now have a pretty decent Fuel Delivery System.

Thanks to Cecil for Helicoiling and rebuilding Jed's Carb, Gary for his two excellent How To's and the ideas there-in and my son Duane for taking some of the pics :D
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