R4 A/C compressor clutch size

[kenh]

So ..... I'm looking at brackets to locate the stock R4 A/C compressor on my 90 truck with the LS swap.

Many of the brackets state they will NOT work with a five inch clutch. MUST use a four inch clutch.

My search skills suck but a look on the inter web reviled nothing to me about this difference. Would somebody be so kind to enlighten me on the difference? Don't really want to replace my "new" compressor if I don't have to. Thanks!!

Ken

 

[1998_K1500_Sub]

When they're referring to a "five inch clutch" they're referring to the diameter of the belt pulley; the pulley's face acts as one-half of the "clutch".

I assume you could replace the clutch on your R4 with a smaller one, if required. The complete assembly is likely required, e.g., the pulley, magnet coil and plate. IIRC, different R4s had different ways of keying the pulley onto the shaft, so be sure to buy appropriately.

For example, here's an R4 with a 117mm (4.6") pulley:

R4 Compressor with V-Belt Clutch

R4 Compressor 1 Groove Clutch, 117mm Clutch Diameter, 9:00 Coil Position, Equivalent to OEM numbers: 15-20230, 2724368

coldhose.com

Here's an example. Attached are drawings for two identical Sanden compressors, one with a 112mm clutch (4.4") and the other with a 130mm clutch (5.1").

As you might expect, installing a smaller pulley / clutch will change the compressor RPM to engine RPM relationship... a "smaller clutch" means the compressor will spin faster, and "spinning faster" could place the compressor into an overspeed condition... "could", during high engine RPM. It's something to keep in the back of your mind.

 

[Schurkey]

I'm looking at brackets to locate the stock R4 A/C compressor on my 90 truck with the LS swap.

Many of the brackets state they will NOT work with a five inch clutch. MUST use a four inch clutch.

If this were me--and it is not--I'd go to a Treasure Yard, buy the entire accessory drive system from a donor vehicle.

This would include the brackets and the accessories that bolt to them--A/C compressor, alternator, PS pump, idler pulleys, tensioner pulley, etc.

Everything is guaranteed to fit, and should cost a fraction of aftermarket brackets.

The stuff I see from the aftermarket "Bling" bracket companies is outright embarassing--poor belt wrap, lack of automatic tensioners, etc. It's like they have high-school kids engineering that crap.

 

[Erik the Awful]

Is there a reason you can't use a stock bracket setup?

 

[kenh]

If this were me--and it is not--I'd go to a Treasure Yard, buy the entire accessory drive system from a donor vehicle.

This would include the brackets and the accessories that bolt to them--A/C compressor, alternator, PS pump, idler pulleys, tensioner pulley, etc.

Everything is guaranteed to fit, and should cost a fraction of aftermarket brackets.

The stuff I see from the aftermarket "Bling" bracket companies is outright embarassing--poor belt wrap, lack of automatic tensioners, etc. It's like they have high-school kids engineering that crap.

Is there a reason you can't use a stock bracket setup?

Schurkey & Erik & 1998
I have the accessory drive for the alternator and PS pump for the LS. So that could work. What I don't have is the mount for for the R4 compressor. Somebody modified a SBC mount to work, but to me it looks a little janky. The stock LS mounted compressor hits the frame. Don't really want to notch the frame. The compressor overspeed thing is/has been in the back of my mind. I did find this setup after an email to the company confirming the clutch size. They have two offerings. https://www.nicecnc.com/products/ls-r4-ac-compressor-bracket-high-mount-kit The company seems to have fairly good reviews.

Ken

 

[Schurkey]

The stock LS mounted compressor hits the frame. Don't really want to notch the frame.

Is there another OEM mounting system that moves the compressor so it wouldn't interfere?

Maybe from an F-body, or a B-body, or a different year truck...or something?

 

[kenh]

Is there another OEM mounting system that moves the compressor so it wouldn't interfere?

Maybe from an F-body, or a B-body, or a different year truck...or something?

Not that I can find. And from what I read the top mount is about the best way to go??? A plus of the top mount is you keep all the factory lines. I don't think there is any one best solution. Anything is going to be a compromise. Holly does make a cast aluminum mount but it's pricey. At least to my Scottish wallet! Holly sells you the mount + a spacer kit and you have to use their belt tensioner. About a $500 give or take. My "problem" is with the stock alt and PS mount the looks are just off/odd so that forces me to buy the matching alt and PS mount! hahaha

Holley 20-131 LS/LT High-Mount Accessory Drive Bracket - A/C, P/S & Alt Brackets - works with R4 compressor

NOTE: This bracket REQUIRES an installation kit for assembly (Part 21-1, 21-2, OR 21-3, see Fitment Guide below for the correct installation kit for your application). Holley is pleased to offer simple, clean, cost effective solutions that solve the accessory drive challenges encountered when...

www.holley.com

 

[Erik the Awful]

Holly does make a cast aluminum mount but it's pricey. At least to my Scottish wallet! ... About a $500 give or take.

Oof. I get accused of exhibiting my Scottish heritage from time to time, but $500 is pricey.