Topic: Dual sheave/pulley alternator

[Gbailey1018]

This image was posted in response to another thread, but I noticed in the image that the alternator has not one but two belts pulling from the engine.  I have a 68 J code 302 4 speed MT with factory AC and thermactor smog system (built in SJ).  When I inherited the car, it had a repro alternator with only one pulley.  However, my water pump pulley has two sheaves and my crankshaft pulley (which appears to be original) has three sheaves, one of which runs to the alternator and the other runs to the AC compressor and the thermactor on one large belt.  The middle sheave is empty.

Does this mean that my alternator should have two sheaves and I should have two belts running from my alternator to my crankshaft, as the image suggests?  What does using the second sheave accomplish if they're both running to the crankshaft?

Not to unnecessarily confuse things, but if it matters I also have reason to believe that my engine had a dual diaphragm distributor (again based on my setup of both factory AC and thermactor) at the factory, but had a single diaphragm distributor since I have owned it.  Is it possible that the PO's decision was made to move from a dual to single diaphragm distributor and that was the impetus for moving to only one belt for the alternator?  Or would those two choices be separate and unrelated?

Hope someone can advise on this, as I need to replace my alternator and would love to know if I need to get a dual sheave.

[Gbailey1018]

Anyone?  Hoping for a reply or two.

[Coralsnake]

Should be the same as the engine used for the 1968 Shelby

http://www.thecoralsnake.com/GT350a.html

A 4spd equipped car would have run the dual vacuum advance

And an AC car used a single sheave alternator pulley

The picture appears to be for a non power steering car, 4spd, no AC

[Gbailey1018]

Thanks for the reply. 

Assuming the diagram is correct, why would there be two belts running from the alternator to the crankshaft if there is no AC and no PS, but only one belt if there is AC?

My car has a factory crankshaft pulley with three sheaves and a water pump pulley with two sheaves.  Would the factory have included pulleys with sheaves that were not meant to be used?  Right now, I have an empty, unused sheave on each pulley.

[Anghelrestorations]

If you have factory AC you are going to have an alternator with only one sheave on your 68.
 
Im not aware of any application where Ford would put pulleys on a car and not have all the sheaves used so its a chance something was changed, rebuilt, removed etc since it was new.  The only other factory option is power steering that is not shown in that diagram but you would obviously know if that was there originally or not. 

[Coralsnake]

The drawing is irrelevant, your application is different. I agree Ford did not leave unused sheaves.

If you look at the chart on the page I referenced it will tell you the pulleys you should have.

From memory it goes like this:

Crank > water pump > alternator

Crank > Water pump > power steering

Crank > air conditioning > smog

[CharlesTurner]

The image is somewhat generic, looks like something from the Ford shop manual or MPC, which can be published before production starts or at a point in production where things may have already changed.


Would recommend when looking at things like this to take them as informative, but would have to be verified with real cars, which includes period photographs or original/unrestored cars.

[Coralsnake]

I guess one to tell if the picture is accurate, look up the correct crank pulley for a 68 J code/4spd/no ac/no ps car

I would guess there is an engineering reason for the dual belt system, as it is used on other applications

[Bossbill]

I have a 67 engine assembly manual which has many details on belt routing for the various configurations.
If available, get the 68 version. It appears few people get this manual.

[jwc66k]

I have a 67 engine assembly manual which has many details on belt routing for the various configurations.
If available, get the 68 version. It appears few people get this manual.

That's because there isn't one.
Jim

[Gbailey1018]

The more research I am doing, the more confused I am getting lol. 

I just read this in the Notes on p. B-2 in Mannel: "Deal belt alternator drive was used in 1965/69 whenever A/C or T/E [i.e., thermactor] was installed without P/S." 

Per the Marti report, my car is J code, 4 spd MT, no PS, factory AC plus T/E.

Doesn't this suggest my original alternator should have dual sheave?  Or does this mean it should be dual sheave if either A/C OR T/E is present but not if both are present?

[Gbailey1018]

Here are some pics of what I am seeing in my car.  Only a few of my parts (e.g., alternator, distributor, AC compressor) have needed to be replaced.  And just as a reminder, my grandmother bought this car new in 1968 and it has been in my family ever since so I have a high of confidence that it has not been stripped or restocked for parts beyond what I mentioned above.

[Coralsnake]

It would have been really helpful if you said no power steering in the original post

[Coralsnake]

Based on the information now provided you should have a double pulley on the alternator and dual belts as shown in the original picture

[Gbailey1018]

Apologies for that omission - I thought I did include that info but obviously I didn't (until my second post.)

Thank you for the reply.  A few follow up questions:

With my factory set up (302 J code 4 speed MT, factory AC + TE but no PS), can someone explain WHY Ford would want two identical belts running the same path from the alternator to the water pump and then the crankshaft?  Does my setup require different more amperage and somehow two belts works better than one for this task?  Which leads me to...

Do I have to have a specific type of alternator such that it can handle two sheaves?  Looking at p. B-10 in Mannel, would the alternator pulley be C5AZ-10344-J?  Or perhaps even C7TZ-10344-B, which it says is for an optional 65 amp "heavy duty Ford alternator in 1968/69" (per Note 15 on p. B-11 of Mannel)?  Or can I simply use my existing alternator and add a two sheave pulley?