Flathead 8BA fuel pump question

H

heck91426

Member
Hey fellas, I am trying to get my late Dads hot rod pickup back together. Its an 8BA with an aftermarket intake (Hexagon). Intake looks like it was designed to fit many years by the number of bolt holes, lack of road draft tube, etc. Can you educate me on the fuel pump and pushrod? How much is the fuel pump pushrod supposed to stick up? looks like i might need to make a spacer. I think he has an early style fuel pump because it has the breather/oil fill? How do i set the height?


Thanks! Mark
 

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that is not an 8ba pump stand its a 59ab drop the assembly on the push rod do not install the bolts now crank the eng over and meassure the amount of lift i i think 3/4 would be good
 
like i said i think 3/4 just a guess may be more like 1/2 i think 1/4 is not enought you can messure the lift on the pump that is needed
 
As stated in post #2, the fuel pump stand you have is not for the 8BA. You mentioned that the intake is devoid of a road draft tube. Just out of curiosity, does it have a provision for a tube and cap to add oil to the engine? If not, that might explain the presence of the early style fuel pump stand. :rolleyes:
 
mcgarrett said:
As stated in post #2, the fuel pump stand you have is not for the 8BA. You mentioned that the intake is devoid of a road draft tube. Just out of curiosity, does it have a provision for a tube and cap to add oil to the engine? If not, that might explain the presence of the early style fuel pump stand. :rolleyes:
Click to expand...

In case the O/P is not aware, 8BA flatheads breath in a reverse manner than earlier flatheads. Many folks don't know this and just toss a cool older manifold on an 8BA without a thought of how the engine breathes. An 8BA draws air into the engine through a filtered oil filler cap. It then circulates through the engine and exits through the road draft tube. In contrast, an earlier engine draws air in through a filtered element on the fuel pump stand, and after circulating through the engine, exits through a vent on the front of the oil pan.

Therefore, when you put an early manifold on an 8BA, you block both the air (and oil) inlet and the air outlet. Most folks simply change to an early style fuel pump stand to solve the oil problem, but the engine breathing problem still exists. Running an engine without proper breathing can lead to early wear, smoking, and increased blow-by. This mismatch of parts should be handled immediately. The usual solution is to plumb a proper PCV system, which is beyond the scope of this post.

I found diagrams of the air flow through both early and late (8BA) flatheads.
 

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Thank you for the responses. Correct, I believe my Dad bought an early style fuel pump stand with breather cap so he could add oil. Do they make a long and short fuel pump pushrod? I can also fabricate a spacer to make up the difference. The PCV / breather system was also something we had talked about. I found some random bits and pieces. I can ask that in a separate post.


thank you for any help. I am still learning.
 
heck91426 said:
Hey fellas, I am trying to get my late Dads hot rod pickup back together. Its an 8BA with an aftermarket intake (Hexagon). Intake looks like it was designed to fit many years by the number of bolt holes, lack of road draft tube, etc. Can you educate me on the fuel pump and pushrod? How much is the fuel pump pushrod supposed to stick up? looks like i might need to make a spacer. I think he has an early style fuel pump because it has the breather/oil fill? How do i set the height?


Thanks! Mark
Click to expand...
572746


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Before you go any further, I would definitely get an 8BA intake for it, hang the '32-'48 Hexagon on the wall. It's not made for your late model flathead, even if it does bolt on.
 
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There are three different lengths of pump push rods. Adding length is not the best. Get the proper length. How long is the rod that is in the engine?
 
Try to get the correct intake and fuel pump mount and push rod for the 8BA. I would encourage you not to try to cobble the push rod length based on guesswork. First, a push rod that is too short will not provide adequate fuel delivery to the carburetor and will progressively pound out the fuel pump lever. Secondly, if the rod is too long, the excess force on the pot metal fuel pump stand can cause it to distort the mounting ears at the base of the stand and actually cause the stand to stretch upwards slightly. I've seen this happen.
 
The pushrod i have now measures a little less than 8" (7-15/16) Thank you for your responses.


General question, does the pump cam come up at a certain degree of crank rotation? (like TDC or BDC??)


Right now this is the intake i have, My dad did have this running at one time with this intake in the garage (Maybe he gravity fed the carbs?? ) I would have to source a stock intake
 
heck91426 said:
The pushrod i have now measures a little less than 8" (7-15/16) Thank you for your responses.


General question, does the pump cam come up at a certain degree of crank rotation? (like TDC or BDC??)


Right now this is the intake i have, My dad did have this running at one time with this intake in the garage (Maybe he gravity fed the carbs?? ) I would have to source a stock intake
Click to expand...

because the lobe is on the camshaft along with the other lobes, it would by necessity, i think, rotate at a given time and interval along with the other lobes, but the timing of a fuel pump's diaphragm movement has practically nothing to do with the timing considerations of the other lobes on the cam. as those involve the opening and closing of valves and issues involving compression and ignition spark.

...that's my take on it anyway. :)
 
Those old Hexagon Tool intakes are few and far between and cool. I understand why your dad (and you) might want to run it. I'm sure you can find the right pushrod between some careful measuring on your own or input from the members of this board. I would imagine the Hexagon Tool intake, being for an early engine, would use the same pushrod as the early v8's. I'm strictly an "8BA guy", so I'm no expert. Once you have that covered, you can attack the engine breathing problem, most likely with the addition of a proper PCV system. Properly done, it is an improvement over the stock "Road Draft" system.

Like the old Burger King commercial, you can "Have it your way". You just have to order the right parts.
 
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