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Belt and AC Questions

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apannizzo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote apannizzo Quote  Post ReplyReply Direct Link To This Post Topic: Belt and AC Questions
    Posted: Jul/11/2018 at 1:59pm
I have a 74 AMX with a 360. The belt that goes around AC compressor and Power steering pump is a little too Big and gives a slight Squeaking noise when accelerated. Does anybody know the correct part or part number for correct belt needed. The belt is relatively new and no more adjusting can be done to pick up slack. Also, when I put AC on Desert mode, there is a squealing coming from AC Compressor by where Pulley on AC Compressor is. On regular AC there is no Squealing. Could this also be related to Belt? Lastly, is there a Low Pressure Switch on this system? If so, where would I find it? Any and all Feedback would be Appreciated.

Thanks Al
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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jul/11/2018 at 2:31pm
Hi, just checking... you do have the idler pulley installed, right? It should be located between the timing cover and alternator, and tensions the belt properly for AC cars.

Billd did answer your question in your previous post about the low pressure switch not being part of AMC AC systems back in the day. He did state you could have one installed at the sight line fitting, as a method to cut off the feed to the compressor clutch, when low pressure condition is happening. It is not stock, but it will do as an option.

71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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apannizzo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote apannizzo Quote  Post ReplyReply Direct Link To This Post Posted: Jul/11/2018 at 3:21pm
Dude,

Yeah for some reason on my end I could not find the First Post I started. It Disappeared! Anyway, OK, there is a Tensioner there. Was looking to try a Different Belt but wanted to get some Feedback. What about Squealing at Desert Mode? Any Advice?
Allan Pannizzo
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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jul/11/2018 at 3:36pm
Originally posted by apannizzo apannizzo wrote:

Dude,

Yeah for some reason on my end I could not find the First Post I started. It Disappeared! Anyway, OK, there is a Tensioner there. Was looking to try a Different Belt but wanted to get some Feedback. What about Squealing at Desert Mode? Any Advice?


Well, having had both a 73 and a 71, 304 engine with AC, the squealing can be by pressure build up from extra cooling. Usually if your belt is a wee small, taking it to a good parts store can measure or compare with a new replacement. 74 is no different than 73, unless your pulley is not factory or a late production from early 75.

I think the 75 had a non serviceable pulley, and may be slightly bigger. You may have the parts counter person pull a 75 belt and a 73 belt to compare with.

I needed a smaller belt for my van, back in 2003, and that's how we got the right fit.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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6768rogues View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6768rogues Quote  Post ReplyReply Direct Link To This Post Posted: Jul/11/2018 at 5:05pm
My 68 290 had an Eaton PS pump and no idler. I think that was added later. I would take off the belt, go to Carquest or other local store, and tell them you want one a little shorter. Our Carquest will measure it and give options for other lengths.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buzzman72 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2018 at 6:01am
Another pertinent question might be...is it factory A/C, or is it American Air? American Air was the dealer installed A/C kit, and might use a different belt.
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akimmet View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akimmet Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2018 at 10:14am
What is the number on the belt currently installed?

Some belts have easy to decipher part numbers, so it could be easy to come up with a part number that is an inch shorter.
Knowing how the numbers work ahead of time is far easier than dealing with a clueless parts store clerk.

As an example:

Dayco 15440 = 15/32" wide 44.0" inches long.
With Dayco numbers, the first two numbers denote width in 32nds of an inch, With 15, 17, and 19 as standard automotive belt widths.
The last three numbers denote the length in inches. The decimal point is omitted before the final digit.




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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2018 at 10:53am
Originally posted by akimmet akimmet wrote:

What is the number on the belt currently installed?

Some belts have easy to decipher part numbers, so it could be easy to come up with a part number that is an inch shorter.
Knowing how the numbers work ahead of time is far easier than dealing with a clueless parts store clerk.

As an example:

Dayco 15440 = 15/32" wide 44.0" inches long.
With Dayco numbers, the first two numbers denote width in 32nds of an inch, With 15, 17, and 19 as standard automotive belt widths.
The last three numbers denote the length in inches. The decimal point is omitted before the final digit.


That is what I was thinking, but was not sure how the codes worked until you explained it.

What I mentioned by smaller, is less belt width. Could fit by length, but may not hold as well, if the factory requires a wider belt. A thinner belt 15mm can make the same length belt as one that is 19mm, fit looser, as the V will seat deeper in the groove, thus making your pulleys seem smaller.

One way to fix an odd fit is to get a wider belt, as long as the belt fits flush, not protruding out from the pulleys.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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PHAT69AMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2018 at 11:43am
Original Post got moved to the HVAC sub-forum section at the top of the Body & Interior Section
( the HVAC sub forum is real easy to miss isolated up at the top of the Body & Interior Section )

A/C Compressor Fan Belt, using the 1967-72 Parts Manual and RockAuto:

With the '72 & Up Lobe Shaped Saginaw P/S Pump:

AMC # 321 5365 = GATES Belt 9640 High Capacity V-Belt;
HC50 15/32 x 64-3/8


With the '72 & Earlier Round Eaton P/S Pump:

AMC # 321 2069 = GATES Belt 9620 High Capacity V-Belt;
HC50 15/32 x 62-3/8
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apannizzo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote apannizzo Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2018 at 1:12pm
OK Got the Belt you recommended. Was able to make it nice and snug. Turned AC on and all squealing gone even in Desert mode and everything is Beautiful!!! Thanks for Everybody’s Help!
Allan Pannizzo
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