Technical Longer Fuel pump push rod needed for Offenhauser 2x2 intake ?

We put an Offenhauser 2x2 intake on our 53 flathead and carbs are not getting enough fuel. Forum member Saxon suggested we may not have a long enough push rod. Looking at the Offy intake the fuel pump mount is 1/4" higher than the stock intake.

I looked at several parts vendors online, don't see anyone that has a longer pushrod.

Help please, thanks-

 

You need to start by measuring manifold and gasket, new and old, to see what's wrong. For '49-53 applications there is only one length, and you should not be confused by the earlier rods because they are considerably smaller in diameter.
All manifolds designed for '49 up use should be same height where fuel pump stand goes on, and all pump stands '49-53 should be same height. Gasket below stand should be thin paper. If your stock manifold worked you need to get back to those dimensions on everything. If the aluminum manifold is higher than stock where pump goes it is machined wrong!
FWIW, early manifolds using the longer of the two pushrod sizes used from 1935 up are same height at rear as '49-53, early short rod manifolds are 1" lower.

 

I threw that out there as a hail mary thought! Strange that it would be a 1/4" difference. Are you sure you measured it correctly? Is this a 8ab engine with a earlier intake and heads?

Make sure you check the throw of the rod as well. Around .25 is the travel you will want.

 

I was thinking that a 1/4 difference MIGHT be achieved by fat intake gasket, wrong base gasket, and outer limit manifold...but also that Offy isn't Offy anymore, and who knows about the machining.
Step one, without question, is careful measurement of stock and Offy manifolds to see if that basic dimension is correct.

 

I called Speedway, spoke with a flathead tech person who said there definitely is not a longer push rod needed with the 2x2 Offy intake. We'll take a closer look at the setup.

Thanks guys-

 

Just measure manifold A, measure manifold B, compare the numbers. There IS only one pushrod length for these.

 

the old timers fixed a worn fuel pump pushrod by brazing some material on it, thus lengthening it.

 

I had fuel starvation problems with my Holley 390 on an Offenhauser intake, and it turned out to be a plugged fuel filter. Just a thought.

 

Im running an Offy regular dual manifold on my 49 8BA with Edelbrock 94s along with the original AC fuel pump rebuilt with a kit from Vanpelts. The push rod is the original and the manifold gasket is a standard Fel-Pro. The fuel pump stand gasket is somewhat thin.
I have 2.5 PSI of fuel pressure on a non liquid filled gauge and good volume of fuel while running at idle. Its hard to really tell where the pressure is at at higher RPMs due to the needle bouncing around somewhat. Edelbrock recomends 3.5 PSI on their carbs. I dont know if thats right or not but the general consensus for Strombergs and 94s are around 2.5 PSI.
I have not experienced fuel starvation problems as of yet.
I had a thread over on the Barn a while back about raising or lowering the pressure by shimming the push rod to raise or shimming the fuel pump stand to lower the pressure and still dont think doing so will change the pressures any practical amount. I did experiment with shimming the push rod to raise the pressure and it did not raise the pressure any measureable amount. I do understand that the diaphram spring will get stiffer the farther it is compressed and so its said will increase the pressure, but as far as im concerned it will be minimal. The only way to increase pressure in my opinion is to experement with stronger diaphram springs.
Bill

 

following...

 

Offy is still Offy. Owned by Fred (Tay) Offenhauser, son of Fred Offenhauser, Great nephew of Fred Offenhauser. They have been in the same location for 50 years and still ues the same tooling to produce the parts.