All Small Six V Belt length - longer VS shorter

[1981 Capri]

Is there any advantage or disadvantage in V belt length . I have a 200cid . The alternator adjustment bracket could have a lot of possible V belt lengths . If i put on the longest V belt that the alternator adjustment bracket would fit , does this have more belt around the alternator pulley ? is there any advantage to a longer belt ? Or could go with a shorter V belt and bring the alternator closer to the engine .
The different V belt lengths would both have the same belt tension .

There is lots of room , is there an advantage to a longer alternator adjustment bracket and move the alternator further away from the engine ?

 

[frozenrabbit]

Long belt would get a little farther from the heat coming off the block. Minimally more amount of pulley contact.

 

[John Ha]

What are your choices in terms of belt lengths that are actually available for a reasonable cost? On the occasions I've had to measure for a belt length, there was only one real choice available that worked with the engine pulley configuration and adjustment distance.

 

[1981 Capri]

John, the 2 belt sizes i have been using for the alternator belt are Gates 7360 - 11AO915 , this belt length is just about at the max bolt adjustment with the original alternator adjustment bracket for a my 1981 200cid engine and looks like the adjustment bolt is at the max , but is not . I mark the alternator and the adjustment mount before the belt goes on, to see if it is at max when belt is tight . Sure looks maxed out / but is not .

Next size smaller alternator belt is the 11AO900 , i am able to get that belt in a Continental 15361- 11AO900 .

John , Not sure what his a reasonable cost !

A longer belt moves the alternator away from the engine but moves the alternator lower . so a tiny bit less belt on the crack pulley .
A shorter belt raises the alternator , as the adjustment bracket is curved . Seeing that the alternator is raised a bit with the curved bracket , then there might be a tiny bit more belt touching the crank drive pulley.

 

[John Ha]

Sorry - I was a little vague about "reasonable price". You can get custom-made belts but they tend to be a lot more expensive than the "standard-length" belts that are normally available at your local chain auto parts store.

I don't think it really matters which of those two belts you use as long as there is adequate slack in the wires that attach to the alternator and there are no interferences anywhere. Personally, I'd choose the one that allows you the best access to the bolt that tightens the alternator on the adjustment bracket. If there's no difference in accessibility, then I'd go for the one with greater belt wrap around the pulley.

 

[DON]

Mmm’. I always went with the shorter one in case the longer one stretched and ran out of adjustment. Maybe in reality they don’t stretch that much. Better safe than sorry

 

[1981 Capri]

John , greater belt wrap ! i notice that when i go with different belt lengths , it moves the alternator closer or further away from the engine , and moves it lower or higher , this changes ( minimal ) the amount of belt that wraps around a pulley . So then what pulley do you want more wrap on , the alternator or the crank pulley .

 

[DON]

I would say the smaller pulley

 

[John Ha]

John , greater belt wrap ! i notice that when i go with different belt lengths , it moves the alternator closer or further away from the engine , and moves it lower or higher , this changes ( minimal ) the amount of belt that wraps around a pulley . So then what pulley do you want more wrap on , the alternator or the crank pulley .

Alternator pulley

 

[sixtseventwo4d]

Although with the belt lengths you are using this may be negligible, a longer belt allows more deflection when running and possibly more frequent adjustments.
If a belt length you are using is unpopular, it can be more expensive (again, negligible) and more difficult to readily get if it should break-so grab a spare!

 

[Frank]

Although with the belt lengths you are using this may be negligible, a longer belt allows more deflection when running

Which makes them more prone to harmonic vibration.
The shortest belt possible is preferred IMO.

 

[John Ha]

The fundamental purpose of a belt is to drive a thing from another thing. It requires friction on each of the two pulleys to perform that function. Alternator pulleys are normally small and the alternator is often working hard, meaning that it's also hard to turn. So maximizing belt contact surface around the pulley (which will also maximize friction between the belt and the pulley) will result in the most efficient drive of the accessory, and extends the belt life by minimizing slippage (and the attendant annoying squeal).

 

[Frank]

Alternator pulleys are normally small and the alternator is often working hard, meaning that it's also hard to turn.

And being a smaller pulley it is geared up several times the crank speed, multiplying the torque to turn it proportionally.