Topic: 1968 Mustang S-Code 390 Fan Belt Routing (Idler Pulley)

[E35Pilot]

I'm working on a 390 rebuild with the following original accessories/options: power steering, alternator, air conditioning, and smog pump.  I have all the original brackets but not the A/C idler gear. I have two questions I'm hoping a few of you experts might be able to help me with.

1. I have the fan belt routing from the 1968 Mustang Part & Body Manual (Forel Pub): cank-A/C-smog, crank-power steering-alternator, crank-water pump.  This configuration requires 3 fan belts.
Question: Is this the only/correct configuration for the fan belts or is there another configuration?

2. The Forel manual shows one tension (idler) pulley mounted to the A/C bracket between the A/C and the smog pump, this is the one I don't have. 
Question: I've seen pictures of big block restorations that had all the same accessories but had a second idler pulley mounted on the power steering brackets.  This second pulley was on the A/C fan belt between the crank pulley and A/C.  Was the addition of the second pulley used on all big blocks (including the 390) or just a few specific models like the 428, Shelby, ect? 

My basic question is...do I need just the A/C pulley for the '68 390 or should I also be looking for the second (power steering pump) pulley as well?

Lee

[J_Speegle]

1. I have the fan belt routing from the 1968 Mustang Part & Body Manual (Forel Pub): cank-A/C-smog, crank-power steering-alternator, crank-water pump.  This configuration requires 3 fan belts.
Question: Is this the only/correct configuration for the fan belts or is there another configuration?

The drawing in the MPC seems to represent the factory routing and number of fan belts needed if you want the original configuration.  Matches the unrestored cars I'm looking at

2. The Ford manual shows one tension (idler) pulley mounted to the A/C bracket between the A/C and the smog pump, this is the one I don't have. 

Question: I've seen pictures of big block restorations that had all the same accessories but had a second idler pulley mounted on the power steering brackets.  This second pulley was on the A/C fan belt between the crank pulley and A/C.  Was the addition of the second pulley used on all big blocks (including the 390) or just a few specific models like the 428, Shelby, ect? 

Might not want to use "restored" cars as a basis for research - especially if that is all your looking at

The idler pulley was used on 68 NJ big blocks with AC that were converted to use as Shelby's if that is what your asking. Don't know if AC was even a factory option on 68 1/2 CJ's built at Dearborn and San Jose after mid production year.  At this point it would ahve helped to know when and where your car was built so we could be comparing "apples to apples"

My basic question is...do I need just the A/C pulley for the '68 390 or should I also be looking for the second (power steering pump) pulley as well?

Sorry don't understand your question. Don't understand why you would need two PS pulleys 

 If you have a 68 390 with PS and AC then if your restoring the car you will need a water pump, crankshaft, AC, PS and idler pulleys to be like original

Guess we have some more things to cover to get you through this -

[E35Pilot]

I knew I would leave out details someone needed.  Oh well, the car was built in late November 67 in San Jose...it was an early car built after the strike.  A lot, if not most of the engine parts, with date codes came from the Jul and Aug 67 time frame.  In fact, the 390 block is date coded Jun 67 and the vin number of the car is stamped on the back of the block. 

Getting back to the question, I want to make sure I only need to to find one pulley for the A/C bracket and not two.  They say a picture is worth a 1000 words...so the address below shows a 428(?) or maybe a 390 with two pulleys:

http://www.428cobrajet.org/id-belts

I just want to verify that I don't need two pulleys for a factor original rebuild for the car.

Lee

[J_Speegle]

Getting back to the question, I want to make sure I only need to to find one pulley for the A/C bracket and not two.  They say a picture is worth a 1000 words...so the address below shows a 428(?) or maybe a 390 with two pulleys:

http://www.428cobrajet.org/id-belts

I just want to verify that I don't need two pulleys for a factor original rebuild for the car.

Looks like your looking at a different engine and year in that picture

I keep coming up with the same bracket that spans between the water pump, PS pump and AC bracket )bottom left in the picture below) only no idler installed on 390 applications

Here are the brackets and idler pulley from a 390 AC engine kit  the 428 kit is different  I believe since the box calls out the 390 specifically





In addition to the MPC diagram that you posted above the instruction sheet from the 69 kit above shows no idler being attached to that three arm bracket only one to the AC support (sheet metal) bracket like in the pictures of the unrestored cars






Hope this helps

[Bob Gaines]

Yes, a lower non adjustable idler pulley was used on the BB Mustang systems from 67-70. Jeff has a picture of one minus a pulley in his posted pic. I know of many who have successfully run without the lower idler for years but the setup works best with. There is a 67/early 68 set up ,a 68/69 setup and a 70 setup. The 67/early 68 setup is what is correct for a late 67 build IMO. All of the brackets and idlers are different then the other systems with the exception of the compressor lower cast iron bracket. The brackets for the others are the same with the exception of the 70 unit has a larger bearing in the pulleys.

[Bob Gaines]

Yes, a lower non adjustable idler pulley was used on the BB Mustang systems from 67-70. Jeff has a picture of one minus a pulley in his posted pic. I know of many who have successfully run without the lower idler for years but the setup works best with. There is a 67/early 68 set up ,a 68/69 setup and a 70 setup. The 67/early 68 setup is what is correct for a late 67 build IMO. All of the brackets and idlers are different then the other systems with the exception of the compressor lower cast iron bracket. The brackets for the others are the same with the exception of the 70 unit has a larger bearing in the pulleys.

I would like to add that the crank pulley and the waterpump pulley and the P/S pulley and the belts I think are different in the system  Jeff shows compared to a 428 CJ and is most likely the reason his is marked for 390.

[Bob Gaines]

I thought I would share some pics of the early style setup .

[ruppstang]

I think that I have a extra 68 idler pulley. I'll post a picture later.

[E35Pilot]

(this is a re-edited post from earlier this morning, after I had a cup of coffee I had to rethink what i had originally saw in the pictures)

These pics are definitely helpful.   

Jeff, so I understand correctly, the pics you show (with the triangle bracket in the lower left of the photo) is this for a 68 or 69 application?  It looks like it has a hole for a pulley but the pulley isn't used. I looked at the pic i posted and it also shows the same triangle-looking bracket attached the to lower A/C bracket.     

Bob, the pics of 67 and early-68 pulleys are helpful.  The second lower stationary idler/bracket seems to be the same triangle-looking bracket as above but with a pulley attached. So 67s had the pulley attached and 68s did not (other then possible early-68 production), correct?   

I guess the question becomes: when did the "early 68" production line end in San Jose?  When did they stop putting the 67 version of the lower triangle bracket (with the pulley) on 68 cars? 

I know there's still more questions/answers yet to be identified, but thank you all for your help so far.

Lee

[mikeljgt500kr]

I thought I would share some pics of the early style setup .

That hardware (bolts and no spacer/washer on the adjustment bolt) on the idler pullet in the first picture is not right for a '67 is it Bob?

[J_Speegle]

E35Pilot as you can see we understand your issue and the difficulty but trying to help

(this is a re-edited post from earlier this morning, after I had a cup of coffee I had to rethink what i had originally saw in the pictures)
Jeff, so I understand correctly, the pics you show (with the triangle bracket in the lower left of the photo) is this for a 68 or 69 application?  It looks like it has a hole for a pulley but the pulley isn't used. I looked at the pic i posted and it also shows the same triangle-looking bracket attached the to lower A/C bracket.     

Yes the bracket shown matches what we see in the MPCs and may be the exact same one but since its in a 69 dated kit is can be discounted - sorry I don't have a late 67 - early 68 dated and numbered kit to share pieces from    this moment But yes accroding to the installation instructions and the drawings in the MPCs that bracket is attached to the lower cast AC mount, the PS mount and I think one spot on the water pump face

The reason why the bracket has a hole though its not used in all applications appears to be by Ford's plan - read below. Other brackets are that way also - one would be the one version of the alternator - Thermactor pump steel front bracket with the two holes while another version has no "extra" holes




Ok next step - Found a Feb 68 and June 67 MPC's and found something interesting. According these PCS both printed when they were making the car the reason we are seeing some examples (Mustang, Fairlanes, Torinos ...) with and some without this second idler pulley is according to the MPCs The Mustang with Thermactor, AC, and PS only was equipped with one while applications like full sized Fords, Torinos, Fairlanes and T Birds received two. Does not make any sense since they are the same engine as should have the same issues but  this supports some of the real car examples I've got pictures of

Its not unusual for the drawings in the MPCs (especially in years after production) to show somewhat generic drawings and to groups similar applications together - just one of the reasons IMHO that the versions from the 70's are so unreliable


What I don't have handy is a Engine Assembly manual from 68 to add to the list

[Bob Gaines]

That hardware (bolts and no spacer/washer on the adjustment bolt) on the idler pullet in the first picture is not right for a '67 is it Bob?

Mike, I haven't seen a spacer/washer used on the adjustable idler like on the alt adjustment bracket if that is what you mean. The witness lines on the many of the idlers indicate type and diameter of adjustment bolt a appear to confirm my observations. Power steering adjustment didn't use a washer ether  . The pictures would be very similar (Pulleys and brackets ) to your 67 BB IMO. Picture of engine is a early 68 GT500.

[Bob Gaines]

(this is a re-edited post from earlier this morning, after I had a cup of coffee I had to rethink what i had originally saw in the pictures)

These pics are definitely helpful.   

Jeff, so I understand correctly, the pics you show (with the triangle bracket in the lower left of the photo) is this for a 68 or 69 application?  It looks like it has a hole for a pulley but the pulley isn't used. I looked at the pic i posted and it also shows the same triangle-looking bracket attached the to lower A/C bracket.     

Bob, the pics of 67 and early-68 pulleys are helpful.  The second lower stationary idler/bracket seems to be the same triangle-looking bracket as above but with a pulley attached. So 67s had the pulley attached and 68s did not (other then possible early-68 production), correct?   

I guess the question becomes: when did the "early 68" production line end in San Jose?  When did they stop putting the 67 version of the lower triangle bracket (with the pulley) on 68 cars? 

I know there's still more questions/answers yet to be identified, but thank you all for your help so far.

Lee

Look again. The lower fixed idler pulley bracket on the 67/early 68(pic) is a single bar looking bracket not triangle shaped. It attaches at two points not three like the triangle fixed bracket. The triangle bracket is the same shape for the later post Dec 67 (still early in 68 production)  it is also the same in 69 and 70.all of the triangle brackets I have seen used on cars had pulleys attached . I can't think of a reason to install the bracket without the pulley because it would not stabilize anything. I do know that many times the brackets are serviced minus a pulley so that the proper indexed pulley (pulley and correct length shaft) can be installed depending on application. For instance the big car upper adjustable pulley is indexed farther out then the mustang version (different belt alignment).  The hang one kit's (Jeff's picture) were designed to be used on more then one application I believe.

[mikeljgt500kr]

Just wondering since I ordered an AMK 1967 390/428 w/AC idler pulley hardware set.  It had four zinc phosphate bolts (with broad base/washer cast in) and two thick washers I assumed were for the adjusting bolt.  I know AMK can get it wrong, so just checking.

[Bob Gaines]

Just wondering since I ordered an AMK 1967 390/428 w/AC idler pulley hardware set.  It had four zinc phosphate bolts (with broad base/washer cast in) and two thick washers I assumed were for the adjusting bolt.  I know AMK can get it wrong, so just checking.

If a wide flange base bolt then there is no reason for washer . They are mostly correct but not always. Better then the alternative. FYI the serrated flange bolts in engine picture follow the witness line found on the brackets before refurbishing (but still there).