Topic: 1967 390 AC idler pulley

[BKnapp]

I have searched and read 2 pages regarding 390 pulleys, but can't find my answer. Can someone get me the dimensions of the adjustable idler pulley? My base is stamped C7AA-8A619-B and I got it from WCCC. However it sticks out 3/4" past all the other AC pulleys and pretty much touches the fan blades.

My set up is about 3 1/8" from mounting surface to outside of pulley. The backspacer on the pulley itself is 1 1/4". I am wondering if WCCC put the wrong pulley on it when the put the new bearing in?

Any help would be appreciated and I can try to get pictures if this doesn't make sense.

Thanks!

[J_Speegle]

Don't think the MPC shows the off set so sorry can't help as I don't have one to measure for you

[BKnapp]

I haven't had any luck in MPC and or Osborn manuals.

[Bob Gaines]

I have searched and read 2 pages regarding 390 pulleys, but can't find my answer. Can someone get me the dimensions of the adjustable idler pulley? My base is stamped C7AA-8A619-B and I got it from WCCC. However it sticks out 3/4" past all the other AC pulleys and pretty much touches the fan blades.

My set up is about 3 1/8" from mounting surface to outside of pulley. The backspacer on the pulley itself is 1 1/4". I am wondering if WCCC put the wrong pulley on it when the put the new bearing in?

Any help would be appreciated and I can try to get pictures if this doesn't make sense.

Thanks!

The C7AA-B is typically for full size car from what I have seen. The Mustang one is shorter. you can modify it and make it work. the short answer is you have to take it apart, cut the bracket down and put it all back together.in the picture the Mustang version is on the bottom and the C7AA-B is on the top.The hex shaped spacer sticks up 3/8 "compared to the C7AA-B  3/4 ". It is hard to tell from the picture angle but the pulley is the same for both.

[J_Speegle]

The C7AA-B is typically for full size car from what I have seen. The Mustang one is shorter. you can modify it and make it work. the short answer is you have to take it apart, cut the bracket down and put it all back together.in the picture the Mustang version is on the bottom and the C7AA-B is on the top.The hex shaped spaer sticks up 3/8 "compared to the C7AA-B  3/4 ".

Guess he's going to need to remeasure since the difference between those two isn't going to equal the 3/4" difference he posted

[Bob Gaines]

Guess he's going to need to remeasure since the difference between those two isn't going to equal the 3/4" difference he posted

Or use the correct adjustable idler pulley.

[BKnapp]

Thanks guys...according to WCCC, the pulley they sent me is correct. However, when I look at their site image the hex shaft is much shorter than what I received.  I am guessing they may be doing as Bob suggested and cutting down it down. Bob, would you be able to tell me the cast # on the correct pulley? I believe the service part number is C7SZ-8678-A. You wouldn't happen to have one available would you?

Thanks!

[196667Bob]

First, let me say that 390 Mustangs are not my "specialty". That being said, here is what I have found in the 1960-68 MPC which may help explain (or possibly confuse more) the dimension issue. It hasn't been noted if you have T/E or not, or if you have Factory (S) A/C or the hang-on A/C (F). I mention this because you will note in my "Text" attachments, there is a difference. I have attached an Illustration of the 390 Mustang Idler Pulley (8678), showing its parts, as well as the Text on the Idler Pulley Assembly and the Bearing and Shaft Assembly (2990). Note that there are two different Idler Pulley Assemblies shown; the C7SZ-8678-A (without T/E), and the C7SZ-8678-B (with or without T/E). The "without: for the "-B" would only apparently apply if the Idler Pulley was mounted on the "Left" (Driver's) side of the engine. The difference in the "Bracket" part of these two Idler Pulley Assemblies is apparently the difference in the hex adjustment casting, one being 3/8" longer than the other. However, the differences in the two doesn't stop here. Note that the "Bearing and Shaft" on the 8678-A is 3/8" shorter than the "Bearing and Shaft" on the 8678-B assembly. Thus if the Idler Assembly in question has the long hex boss, and the long "Bearing and Shaft", there would be 3/4" difference. Just a thought on how the 3/4" difference could occur.

Bob

[BKnapp]

I am not an expert either...obviously. I think I am becoming an expert in everything NOT Mustang. I do have factory AC. My understanding is that one idler pulley is fixed and this would be common to both w or w/o TE. The w/o TE pulley is the adjustable pulley located toward the passenger side. The fixed pulley mounts to the block and does need to be longer. The adjustable pulley mounts to the lateral AC bracket and needs to be shorter. I will take ANOTHER Look through the MPC and Osborn manuals, but I have been looking at so many pulley and bracket numbers without having the car in front of me. I am going to pack everything up and head over to the garage so I can have a visual.

Thanks!

[J_Speegle]

Just a few pictures of San Jose examples that may or may not help in some way.  For others please ignore the collection of non-factory details also shown in the following pictures








Example with thermactor




Though it looks like the same/similar picture as above - one without thermactor





Hope this helps in some way.

[BKnapp]

Thank you, Jeff. It certainly confirms the shorter hex boss and the fact mine is longer. What I cannot figure out is why the one image at WCCC (appears to be short like those pictured here) has the same casting number as mine, but mine is 3/8" longer. I doubt ford had the assembly line guys cut 3/8" off the part. I am guessing WCCC goes through the process Bob G suggested. I guess I will search for the C7SZ - A part. Hopefully WCCC will work with me, as these are not cheap.

I always appreciate the help and pictures.

Bill

[Bob Gaines]

A/C pulleys is not my first language and typically I go by what it looks like instead of engineering number . With that said the non modified shorter Mustang version adjustable idler I have has a C4AA prefix engineering number with the suffix is unreadable or not there.  Even with my magnifying glass I can't tell a letter. I should have written it down but I seem to remember a C7ZA engineering number used on some of the  short ones  but can't be sure . I haven't had to modify any for a couple years because I found enough of the short ones to fill my needs. I will reach out to the person i sold a set to recently an ask if there is any difference on his engineering number. This is the only pulley C4 marked one I have and is matched up with a NOS fixed pulley ,upper 67 / 68 until March compressor mount and lower 67/68 compressor mount .  I plan on selling as a entire set. I am sure WCCC will work with you . They must have forgot to modify it like they did their example. If for some reason you can't get it figured out you can send it to me and I will do it N/C when I set up to do the several I have here to do. Bob

[Bob Gaines]

First, let me say that 390 Mustangs are not my "specialty". That being said, here is what I have found in the 1960-68 MPC which may help explain (or possibly confuse more) the dimension issue. It hasn't been noted if you have T/E or not, or if you have Factory (S) A/C or the hang-on A/C (F). I mention this because you will note in my "Text" attachments, there is a difference. I have attached an Illustration of the 390 Mustang Idler Pulley (8678), showing its parts, as well as the Text on the Idler Pulley Assembly and the Bearing and Shaft Assembly (2990). Note that there are two different Idler Pulley Assemblies shown; the C7SZ-8678-A (without T/E), and the C7SZ-8678-B (with or without T/E). The "without: for the "-B" would only apparently apply if the Idler Pulley was mounted on the "Left" (Driver's) side of the engine. The difference in the "Bracket" part of these two Idler Pulley Assemblies is apparently the difference in the hex adjustment casting, one being 3/8" longer than the other. However, the differences in the two doesn't stop here. Note that the "Bearing and Shaft" on the 8678-A is 3/8" shorter than the "Bearing and Shaft" on the 8678-B assembly. Thus if the Idler Assembly in question has the long hex boss, and the long "Bearing and Shaft", there would be 3/4" difference. Just a thought on how the 3/4" difference could occur.

Bob

The difference I see when working with them is not the pulley but the bearing. The pulley portion is common between a number of different application brackets. The bracket portion is what changes not all but many times. The bearing is the same but the shaft is longer on one compared to the other . When modifying the longer hex style bracket to become the short Mustang style not only do you have to cut down the hex pedestal but you have to cut down the bearing shaft if reusing or get the shorter style bearing used on the Mustang bracket. The longer shaft bearing if left the same will stick out the other end of the shaft hole and the bracket will not sit flat.

[krelboyne]

Thank you, Jeff. It certainly confirms the shorter hex boss and the fact mine is longer. What I cannot figure out is why the one image at WCCC (appears to be short like those pictured here) has the same casting number as mine, but mine is 3/8" longer. I doubt ford had the assembly line guys cut 3/8" off the part. I am guessing WCCC goes through the process Bob G suggested. I guess I will search for the C7SZ - A part. Hopefully WCCC will work with me, as these are not cheap.

I always appreciate the help and pictures.

Bill

Brian, we will work with you. I am here to learn like everyone else. Scott

[BKnapp]

Brian, we will work with you. I am here to learn like everyone else. Scott

Thanks, Scott. Darrell has already reached out to me and I will get it to you guys this week. It is so nice to work with vendors that really want to do right by the customer. It is becoming a scarce quality and I truly appreciate it!