Oil pump drive size lesson

[turbohunter]

Sorry guys, more questions.
Why do FE pump drives come in two sizes (1/4, 5/16)?
I ssume 1/4 is standard, what were the applications for the 5/16?

[thatdarncat]

FT big truck engines ( 361, 391 ) use a 5/16 drive. Oil pump and distributor use the larger size. FE passenger car and light truck ( 360, 390 ) engines use the 1/4"

[turbohunter]

Makes sense, thanks.

[ScotiaFE]

You can also use a FT 5/16" drive pump on an FE with the custom drive shaft.
It's really just the same pump with a thicker hex.

Melling FE Pump specs

M-57 STD Volume Yellow Spring 40-45psi  1/4" Drive

M-57B Std Volume Brown/Plain Spring 60-65 psi 1/4" Drive

M-57HP Std Volume Big Blue Spring 100-110 psi 1/4" Drive

M-57HV High Volume Brown/Plain Spring 60-65 psi 1/4" Drive

M-57A Std Volume Brown/Plain Spring 60-65 psi 5/16" Drive

M-57AHV High Volume Brown/Plain Spring 60-65 psi 5/16" Drive

[turbohunter]

As a matter of fact I just ordered one from Precision