Technical Eliminating a Flathead Mechanical Fuel Pump

Found this interesting Topic. Seems like a good idea.

Source: http://www.precisionenginetech.com/project-engine-builds/2010/09/02/project-flathead-part-2/


IMPORTANT FLATHEAD FUEL PUMP NOTE!

The original location for the mechanical fuel pump is at the top rear of the intake manifold. The fuel pump mounts atop the intake manifold, and the fuel pump pushrod engages the cam’s eccentric by passing (vertically) through a steel bushing located in the rear floor of the lifter valley. The steel bushing features a machined groove around its outer perimeter, with a small orifice hole in the groove. The groove allows oil (pushing up through the main passage) to pass around this groove and run forward through the lifter oiling tube. The small orifice hole in the bushing allows feed oil to enter the bushing inner diameter and lube the fuel pump rod.
This bushing would have been removed prior to block machining/cleaning and must be reinstalled.
However, the OE style mechanical fuel pump may not be sufficient to feed a multiple-carb setup (making an electric pump the wise choice).
It’s important to note that if you don’t run the mechanical fuel pump, the small oil hole in the bushing will allow oil to escape under pressure, resulting in a slight reduction of oil pressure (I admittedly don’t know exactly how much of a drop would occur). So, if you don’t plan to run the mechanical fuel pump, you need to block this small orifice hole in the bushing (via brazing) before press-fitting the bushing into the block.

The factory bushing at the fuel pump shaft bore is seen here. This needs to be modified if you plan to run an electric fuel pump, and to install a breather tube at the rear of the intake manifold at the OE fuel pump location.


Here is the OE fuel pump shaft bushing removed from the block. The circumferential groove allows oil to flow to the valley oil tube, while the small orifice provides oil feed to the mechanical fuel pump shaft. If you plan to install a breather in place of the mechanical fuel pump, this orifice hole must be plugged. This can be accomplished by brazing the hole shut.


I opted to make an aluminum sleeve that is interference-fit into the OE bushing. This is simply an alternative way to block off the orifice hole. I machined a stop-hat at the top to prevent accidentally driving the sleeve too far into the bushing.

I will admit that I didn’t realize this problem until after reinstalling the cleaned bushing into the block. Rather than remove the camshaft and the rear cam bearing (in order to drive the steel bushing out of the block again), I decided to take an easier route. Since the goal is simply to block off the small orifice hole in the bushing, I made an aluminum insert tube on my lathe. The tube press fits into the bushing, leaving the vertical drain hole open (from lifter valley to rear cam bearing) while still allowing oil to run around the bushing’s outer groove. In my particular case, my steel bushing’s I.D. measured 0.441”. I machined the aluminum tube with an outer diameter of 0.4425” (for a 0.0015” interference fit). I started with a 0.500” O.D. aluminum tube, machining the main body down to the 0.4425” O.D., but leaving a 0.500” diameter top flange (hat) to serve as a dead-stop during installation. I also turned down the bottom tip area of the tube to 0.040” (about 0.250” from the bottom) to aid in initial entry and centering.
If you opt to make this insert tube, use my dimensions as a general reference only, since your pump rod bushing’s inner diameter may differ. Original factory tolerances and age can easily combine to result in bushing diameter variance. Measure your bushing I.D. first.
Of course, if you bothered to read this, you’ll already be aware of the procedure, so brazing the orifice shut will be the simple solution, in which case you won’t need to fabricate this insert tube.
I wanted to mention this so that you’re aware of the need to block off the small oil feed hole in the fuel pump rod bushing in case you don’t plan to run the mechanical pump. If you braze the orifice shut before installing the bushing, be sure to carefully grind the braze area flush with the bushing’s outer groove to avoid blocking oil flow around this groove.

 

Does this plug need to be hollow or could a solid plug be used?

 

The hole is allow oil to still splash into the cam bearing area where the fuel pump rod used to ride. It would have to splash here since it is higher than the lifter gallery drain hole at the back of the block. May not be necessary, just a precaution. Cam bearings get oiled from other holes.

 

I'm sorry, but am I wrong to say that a simple aluminum plug is the simple solution here?
I know there are vendors that sell them for this specific purpose (my buddy bought one).

 

Yep the plug may do the job just fine.

 

Granted, this is a minimum of oil we are talking about, but why not send more oil elsewhere if its not being used for the push rod.

 

Flatheads up through '48 do not have the hole and even the bushing is not exposed to pressure. '49 up types MAY have the hole, not nearly all do, and the outside of bushing is exposed to pressure there. Hole is pretty small to have any noticeable effect, but plugging it would fix a potential miniscule leak. If not running a pump I would cap off the pushrod hole itself, or perhaps just leave in a pushrod (early engine) with bottom and top cut down so the stock umbrella remains. The possible issue, probably not a real one but easy to eliminate as a concern, is oil splash/spry coming into valley. I doubt that it could be significant, but who knows...flatheads do not like any extra oil mist in the valley, hence the lower shields and the vent tubes, because it is easy to overwhelm the guides and get oil burning.
And...extra pump needed for multiple carbs?? Maybe for priming if they are dry. Sounds like primitive 3 carbs must flow lots more gas thinking...any change in proper setup would be the minor amount from extra power (only when it is used, of course...going down the road at 60 still takes exactly the same power) and in minor discrepancies in the fuel curve from idle-main-power circuit transitions.

 

Bruce, I'm running my 8BA with the pushrod cut down as you suggest, and it works ok. Bushing still in place, and if some need arises to return to the stock configuration,
it's an easy fix.

4TTRUK

 

I think that's all that's needed, likelier to cover fears than other problems. Just elimintaing a doorway for more misting upstairs.

 

There is considerable debate9 Fordbarn and here) as to whether or not the bushing needs to be plugged depending on if the engine is an 8BA or a 59AB style. On my 8BA I did not plug the bushing and did not lose oil pressure. When the oil filler screw cap you see in the photo is tightened down, the other end covers the bushing hole preventing mist in the valley. Been that way since 1999. No problems.

 

I have no opinion of what to do. I just offer the insight that there is no oil pressure to the rear cam bearing or the drive gears to the oil pump. All are lubed by oil getting out of the top of the oil pump and circulating enough to do the job. The fuel pump push rods have huge clearance to the bushing ID. The hole in the bushing may be for lube to the cam bearing. I sure don't know. I have a 59AB and run the rod and the pump. I run a PCV system and will also go to an electic pump at some time. I don't know what I will do with the rod.

 

However, the OE style mechanical fuel pump may not be sufficient to feed a multiple-carb setup (making an electric pump the wise choice).

Not so I am running 4 x 2 97 carbs on my flathead with a new mechanical pump no problems.

As for the fuel pump push rod bush the easiest way to block it, if running an electric pump to stop oil splash up your breather is the install a core plug, the core plugs used on the early SBC rear oil gallery passages are the correct size, can be knocked in place without removing the intake.

 

I have never found a hole in the bushing.. I always check for it..probably 15 Flatheads..mainly early but a few 8BAs too.
tend to agree that on a street flathead a new mechanical pump supplies plenty.

 

Geography 101: on '32-48 there is no pressure in sight there, and bushing is in iron so even a missing or incredibly worn bushing cannot affect pressure.
On 8BA, bushing intersects main oil gallery so that grotesquely excessive and unlikely wear could cause a real pressure leak. Some unknown proportion of late engines have the little hole into the bushing bore (betcha that on 75% of engines on the road some stray speck of lint has plugged it anyhow) which is a theoretical tiny concern.
In both engines I worry about anything that might allow more direct misting or splash into valley and I would keep a truncated pushrod in place just as a shield. I do know of good flatheads that burned oil from new rebuild, and stopped burning oil when it was discovered that the little floor umbrellas were missing from the valley and they were replaces. Clearly extra oil from any source upstairs is potential trouble, so just make a simple umbrella for that hole.
My preference is for a stock pump with a backup electric...stocker if right is entirely sufficient for normal level street engines, but is not great at filling up carbs that have evaporated to empty in a period of rest. The electrics are great for priming and of course offer an instant repair if ethanol eats your pump...

 

On my 32 with the flathead V12 I have the mechanical and an electric fuel pump to primer the lines than switch to the mechanical. On my 53 Flathead I installed an electric fuel pump and illiminated the mechanical with a plug similar to a small freeze plug.

Frenchy

 

Bruce and Frenchy,

The electrical fuel pump for priming after long sits seems like a good idea, (except for purists) Does the mechanical pump pull thru the electric when it is turned off or does it bypass around it with some sort of valving arrangement?

 

After I have primed the carburetors with the electric fuel pump I turn it off and I use my mechanical fuel pump there after with no issues.

Frenchy

 

I just use a OEM mechanical pump to feed the 2x97's I run and it's more than enough. However the pump I've got has an in-built primer lever and that is a brilliant feature for if the car sits for any length of time - 6 pumps and she's good to go! It seems these pumps are quite rare - Canadian I think.

 

The pumps with priming levers are British in origin, I think if Canadian mostly military because Canadian WWII stuff was built to common Imperial standards (including RHD) even though Canada was the main supplier of everything Ford.
Pumps...some E pumps will work as draw-through (though I suspect some drag would be added on the weak suction side of the mechanical pump), most will not.
Look at Rumbleseat's book: http://www.flatheadv8.org/rumblest/intro.htm
Click into the fuel section and look over his pump scheme.

 

This thread is golden.
Oh How I miss Bruce with his knowledge and humor.

 

Pete to Pete!! X 100!!!