HEMI oil pump drive

I've seen the 5/16 hex on a HEMI pump drive break more than once but for the first time for me I broke the Mag drive slot (not the mag base) in the pump drive. The combo is a 525 blown/inj HEMI with a Mag 3. The mag and base turn as would be expected. This was not a New drive but a used, I don't remember if it came with the blown parts I purchased years ago to build this motor or one I had for previous applications. That being said is this typical of a drive used with a mag (first time using a mag) or has someone experienced some other issue creating this warning sign?

 

BTW this is a two piece (Mag Base /Pump drive) design not the "Enderle" Mag base pump drive one piece shaft design

 

Anything picked by the oil pump can break it

 

The pump spins fine, My experience is when the pump jams/fails it twist off the Hex because the engine keeps running (with 0 oil pressure), that did not happen in this case I could spin the rotor in the Mag, it broke the tangs off the top of the shaft (in the Bronze gear) creating a no spark condition due to the mag not spinning

 

I don't have an answer to your question but it's a hell of a lot cheaper than breaking off the 5/16" hex end...

The tang end looks like it was a quick fracture in the picture. Maybe a material issue or lack of radii at the root of the tang?

Chris Saulnier - Team Tigges
Mechanic Falls, Maine

 

I agree 100% but never seen this happen prior nor anyone I
know. Ordered two replacements so we will see how it goes.

 

Purchased two new drives and both came with Over size Hex (one at .324 and the other .320) kinda tough to fit into a .312 broach...

 

Had to "Resize" them on the Bridgeport. I talked with Milodon and they said .319-.320 is to print. There wa no way .320 was going in the pimp (cast KB) Seems something has changed, the broken one measured .310. Its behind me now so all is good.

 

Broke 1 side of the tang in a super mag hemi 10 years ago. Done know why in the burn out

 

I broke (2) on a 417 Donovan. I suspect it was a runout issue, between the pump drive and the mag. Maybe something not machined concentric and perpendicular. My fix was to broach a hex through the bronze drive gear and run a hex on the mag shaft, using a hex coupler.