Pulley size for 1/2" belt

Trent Couch · Apr 17, 2015

Does this look like this pulley fits the belt correctly on my delco alternator?

Janicholson · Apr 17, 2015

I think it looks correct. Belts have been standardized at 40 degree included angle "V". GM pulleys tend to have a Bell outer edge that helps keep belts on the pulley, and absorb some alignment issues. If it drops into the pulley too far and is effectively running on the surfaces below the 40 Degree sides, it is too narrow for the pulley. Jim

Trent Couch · Apr 18, 2015

Thank you Jim see the pulley i have that came in the 12 v kit says its 5/8" wide but the belt I have is only 1/2" so thats why I was asking

Jim Becker · Apr 18, 2015

I can see a gap between the sides of the belt and the sides of the pulley. Is the belt pulled down as far as it goes into the pulley? If so, the belt is bottoming out in the groove because the pulley is too wide. This is what Jim was talking about in his last sentence.

Some of those pulleys have two separate sides with spacers between the two sides. If yours does, you can disassemble and move one or more spacers to the outside of the pulley. If not, you need to start looking for another pulley. This is assuming you have a belt that fits the other pulley correctly. If you have the same problem on both ends, get a wider belt.

Trent Couch · Apr 18, 2015

Yeah I see what u mean thats why I was concerned that the pulley was to wide and as far as adjusting the pulley width The
pulley is one piece its not split where you could adjust it. would the pulley on the right in this picture be what I need?

rustred · Apr 18, 2015

that belt looks too narrow. it cannot bottom out on the pulley, as it is driven from the sides. how does it compare to the tractor pulley? if its the same then need wider belt. the pulley on the right looks more correct.

Trent Couch · Apr 18, 2015

The tractor pulley fits correctly and is driven from the sides but this pulley as you said is bottoming out now I just need to get the correct pulley the pulley in the picture is 1/2" belt width and 3-3/16" pulley O.D im hopin this is the correct pulley I need

Bhunt · Apr 18, 2015

(quoted from post at 17:12:34 04/18/15) The tractor pulley fits correctly and is driven from the sides but this pulley as you said is bottoming out now I just need to get the correct pulley the pulley in the picture is 1/2" belt width and 3-3/16" pulley O.D im hopin this is the correct pulley I need

The pulley you have on there looks smaller than 3 3/16 Outside diameter of the new one your looking at. It looks like you still have a good degree of slack in it do you have more adjustment inboard? If you don't have more adjustment inboard it may not fit and you may have to get another belt. I do agree the pulley you have is to big for that belt. I'm guessing there are no pulleys at Napa or auto zone that are readily available? It does take a good degree of Patience and you appear to be meticulous with your work that's a good thing. When you get it all together write down that belt number
Good luck Byron

gbs · Apr 19, 2015

take the pulley to the nearest starter alternator rebuild shop, if it's the right diameter you need they can match up one for a 1/2" belt, if it happens to be a stamped pulley that's a common size it will cost very little if anything,also due to slight belt width or pulley width variations the belt may fit a little low or a little high in the pulley.

John M · Apr 19, 2015

IF you can get the belt tight, and the hood on, don't worry about it.

Pulley size for 1/2" belt

Trent Couch

Member

Janicholson

Well-known Member

Trent Couch

Member

Jim Becker

Well-known Member

Trent Couch

Member

rustred

Well-known Member

Trent Couch

Member

Bhunt

Member

gbs

Member

John M

Well-known Member

Similar threads