Topic: 68' GT390 Alternator Pulley

[somethingspecial]

When I built my 68' GT390 GT/CS, I contacted a very well known Restoration Parts supplier and he told me the alternator should have a double groove pulley.  The car is equipped with PS, and has thermactor smog pump, no A/C.  With these accessories, the belt routing only uses one groove on the alternator.  During judging, it has been mentioned to me I have the wrong pulley, but no deduction was issued.  Should I have a single groove pulley, which I do have on hand, or should it be the double groove pulley with only one groove used?  I show this car in Concours Trailered Div. and want it to be absolutely correct.  Thanks for any help.  Mike

[nham3407]

MY 67 GT S-code 390 Thermactor car also has the double grove alternator pulley.

[somethingspecial]

On mine, The rear belt drives the water pump and alternator, the middle belt drives the powersteering pump from the water pump, and the forward belt drives the smog air pump.  The only belt from the crank pulley is the Water pump, alternator belt.  Mike

[DTruitt]

It should be the double groove pulley. When ordering the belts you need to order them as a pair, if not they may not seat evenly in the pulley.

I have to stress a matched pair (I ordered directly from Marti Auto Works) cause some venders will just send two belts!
 
Danny

[somethingspecial]

Looking at the photo again, it makes sense now.  I have the routing wrong.  Looks like I need to change the PS belt to the crank pulley and order two new belts for the Alternator, Correct? This expains why I have empty grooves on the crank pulley.

[DTruitt]

Yes, Mike, if you have the correct water pump pulley (3 groove), and crank pulley (3 groove) you should not have any unused grooves. Before you order the new belts check to ensure you have the right P/S belt also and it fits. It should be on the forward crank pulley groove which is a smaller diameter than the alt. grooves. The picture is the same routing as my '68 390 GT.

Sounds like you'll have this resolved soon.

Danny

[somethingspecial]

Thanks Danny, All these years I have had empty grooves on the crank pulley and it has bugged me.  Both water pump and crank pulleys are three groove and original to the car.  Your help is greatly appreciated.  Mike