1970 Hemi roadrunner alternator

[Lucky Lar]

Does anybody know
if the 70 Hemi Roadrunner Alternator had 1 or 2 pulleys
I have seen a lot with 2 pulleys including mine, but of course there is only one belt???

 

[Jerry Hall]

Stock had a single pulley.

 

[R413]

1970 Hemi alt had dual groove pulley, and they had one belt and used the outer groove.

The water pump pulley is different than most big blocks. You can see more of the pump and bolts because it doesn’t go back as far.

1969-1971 Apia’s different than 1966-1968.

 

[Lucky Lar]

Thanks for the replies

 

[HEMI RR]

I just went through this; an original uses a double groove pulley with the belt using the outer pulley. Also, all pulleys are different that a big block . However, you can make it work with big block pulleys it just is not correct. All the pulleys are available aftermarket. When I converted to power steering I purchased a Hemi power steering pulley and that is where the great adventure started for me.

 

[RJRENTON]

Gentlemen,
I believe the oem Hemi engine alternator pulley, aka sheave, is a Deep groove double groove unit. The belt runs in the outer gtoove. The deep groove design was to prevent the drive belt from being thrown off at high engine RPMs. The water punp sheave has a smaller O.D. and subsequent smaller Pitch Diameter to spin the pump faster for better block and head coolant circulation. Just my opinion of course.
Bob Renton

 

[Dragon Slayer]

The OEM correct hemi alternator pulley 69-71 is double groove 3" part #2095059. I see a lot of cars with the aftermarket double pulley on aftermarket alternator. Works, just not OEM appearance. Correct pulley picture attached, notice how the hub for removal and installation is recessed into the pulley; not sticking out like a nose on some of the non-hemi versions.