GM r4 pancake to sanden conversion

[weq92f]

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My '67 BBC SWB has killed another one of these GM r4 A/C compressors. The accessory drive is a GM serpentine cast iron unit much like late 80's and 90's GM trucks and SUVs with the compressor mounted on the passenger side, idler pulley at the very top and tensioner pulley below the compressor. The truck has Vintage Air internals.

I'm definitely tired of replacing these r4 units when they quit so looking to convert to a sanden 508 or equivalent unit that will retrofit into my brackets and clear the valve cover.

All of the conversion brackets I'm finding Online are for SBC where the tensioner pulley is on top. I've read Online that these brackets will not work on the BBC for reasons not specified.

Anyone here have any experience or advice for my delimma?

I found this also...one guy out there with same problem and he home-grew his own solution some 12 years ago. I'd rather just purchase the right hardware if available but I can't find it!

https://www.hotrodders.com/threads/c...sanden.525501/

-klb

Don't mind the dirt/dust...it needs a good cleaning...

[xylorex]

Check out the dirty dingo sanden bracket they make, I have it on my sbc serpentine setup.

You can copy the kit, or buy it and just modify what you have to. I needed to raise my compressor up some, so I had to make a new set of plates.

[weq92f]

Originally Posted by xylorex

Check out the dirty dingo sanden bracket they make, I have it on my sbc serpentine setup.

You can copy the kit, or buy it and just modify what you have to. I needed to raise my compressor up some, so I had to make a new set of plates.

Thank you. I did see that one but it stated explicitly does not work on BBC with steel bracket. Hoping to find something that will work out of the box.

-klb
Posted via Mobile Device

[weq92f]

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Gonna make the sanden fit into my existing r4 bracket. I made a template to identify what needs to be cut out of it then drilled holes to effect a cut along the curved lines. Once that was done, I used an angle grinder to detach the bulk of what needed to be removed. It's not pretty but it is going to work.

Next will be some more cutting to accommodate the rear ears of the sanden unit.

-klb

[xylorex]

i have haven't already, you may want to mock it up before you get too much further.

the reason i had to raise mine up extra is because the sanden is much longer than the r4, it was hitting my valve covers.

attached are a few photo's i found on my phone

[weq92f]

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The modified mount, when completed, should still work with an r4 if necessary.

I have mocked up and measured things to the extent possible without a fully modified bracket. The valve cover clearance is an issue that may come into play. It's going to be very close. I am prepared to shim a little bit forward toward the radiator but going up isn't going to be an option.

-klb

[RichardJ]

In my opinion, it isn't pretty and it isn't going to work. What you have there is scrap metal.
>>I am prepared to shim a little bit forward toward the radiator<<
You can not misalign a serpentine belt and expect it to live.
R4 compressors may not be the best, but they are not the worse. You just need a better r4 rebuilder.

Find a replacement bracket, get a better r4 and make sure it is installed correctly.

[weq92f]

Originally Posted by RichardJ

In my opinion, it isn't pretty and it isn't going to work. What you have there is scrap metal.
>>I am prepared to shim a little bit forward toward the radiator<<
You can not misalign a serpentine belt and expect it to live.
R4 compressors may not be the best, but they are not the worse. You just need a better r4 rebuilder.

Find a replacement bracket, get a better r4 and make sure it is installed correctly.

Regarding shimming: if I need an 8th or less I can shim everything. The driver side and passenger side cast iron bits that bolt to the heads. All accessories hang on them. Then the crank pulley and water pump snout pulley. I don’t want to do this but I might if necessary.

This bracket I’m cutting up may as well be on if a kind. Replacements are out there but they are expensive. If this all goes to shat, the other options are even more expensive. Lol

It will work. It’s been done by another bloke out there( see first post ). Now if I screw up this heavy cast bracket that’s on me. If I don’t, it will work.

Take care,

-klb
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[weq92f]

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First test fit of the assembly ( the modified cast mount plus 3/16 stamped steel plus compressor ) mounted to the head. Ima need to clearance the valve cover just slightly but this right here is success in my book. The pump is solidly mounted to the bracket along 3 of the front 4 ears using the unmodified r4 front holds in a 3/16 stamped steel bracket that attaches to the modified cast iron bracket. Additionally there are two ears mounted to the cast iron bracket in the rear of the pump. It should hold fine.

-klb

[weq92f]

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Had to relief one of the sanden head bolts a bit and shim the sanden back an 1/8 to align the pullies.

Turned the motor over several times and the belt is still there! It may take another iteration of the shimming but it will not be much more or less. Gotta drive it with A/C going to be sure. Had to use the next size larger belt to get the right tension.

The sanden should perform better with less drag and is much more reliable.

Now on to flushing everything I'm not replacing and getting it all put back together.

-klb

[Richard]

Sanden has a replacement head for their 7 piston 508 that accepts the R4 manifold here on the website https://www.dirtydingo.com/shop/adva...B-R4&x=24&y=10 Have some more inks in this thread https://67-72chevytrucks.com/vboard/...d.php?t=844474 post #20. The 7 piston 508 is real close in displacement to the R4. After 2 remans basically DOA and the Delco replacement R4 only lasted 2 years. I am done with them.

[weq92f]

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Finished up the final tuning of the AC today...Using specs from Vintage Air, I was able to achieve 42 degrees F at the vent while seeing 18psi low and 250psi high...this at just over idle sitting still...it will get better at cruise speed. This at 98 degrees ambient.

The total charge was right around 1.8 lbs or 2 12oz cans of 134a w/no additives.

I also placed an electric pusher fan on the new parallel flow condenser which I'm sure helps those standing still pressures quite a bit.

I'm totally thrilled with this conversion and the final results. Time will tell how much more reliable this unit is over the old factory stuff.

-klb