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Big Blocks And Air Conditioning

5K views 35 replies 6 participants last post by  toobroketoretire 
#1 · (Edited)
Are any of you running big blocks with air conditioning? And if so do you still have your smog pump going? If not then you should have it going because the smog pump and it's belt play a vital role for those cars with air conditioning.

Shortly after I got my '71's air conditioning going I took a trip to Fresno with the air conditioning on and by the time I got there my alternator belt had burned up. Burned up so bad my fan was barely turning and my a/c compressor had come to a complete stop.

Looking the situation over after I got back home I realized the compressor was driven off the water pump pulley only as the belt didn't go around the crankshaft pulley like it does on a small block. My smog pump and it's belt had been removed by a previous owner and without it operating the only belt left to power the water pump, fan, alternator, and compressor was the alternator belt. And that's why it burned up. Way too much load for a single belt.

So I realized I needed to put a belt in the empty rear pulley grooves and use an adjustable idler pulley to tension it. I bought an idler pulley off a 1970's Chrysler product then fabricated a mount bracket with a means of adjusting the pulley. Now the new idler belt provides 50% of the drive power and the alternator belt provides the other 50%.

I had tried to post pictures of my new idler pulley but for some reason it wouldn't accept them. So I'll try again later in the day....................
 
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#11 · (Edited)
C'mon guys. Am I the only one here running a big block? There has to be a few others besides myself. If you own a big block be aware it's a big mistake to remove your smog pump and it's drive belt as that belt provides 50% of the drive power to the water pump's pulley. And regardless of whether you have A/C or not the big 7-blade clutch fan alone draws more power than the alternator belt alone is capable of handling.

If yours is missing the smog pump and it's drive belt you can either make your own idler pulley setup like I did or I'll make one for you for $175. I'd like to make them for you for free but as each one takes me about 6-7 hours I'd have to get paid for my time and parts. The $175 would include all of the parts needed and the shipping cost to any of the lower 48 states.

The only information I will need is the water pump's pulley diameter, the belt width, and whether or not it has A/C.
 
#13 ·
fatguy has "2/80 AC"...as in roll down 2 windows and go 80mph...and i am going to run electric fans again so im not worried about the waterpump belt slipping. if it does i will weld it to the pulley, that'll teach that little critter to mess with me....whaddaya mean you cant weld rubber to steel? says YOU..... :thumbsup3:
 
#16 ·
I do have a BB- but no A/C. The rear belt on my w/p is a captured belt- crank and w/p only- front groove on the w/p pulley and crank also do the p/s, and a single short belt from the p/s to the alternator.
No idler and all real short runs on the belts.
 
#23 ·
I am a mechanical engineer (retired) and I can tell you first hand nobody in the right mind would ever design a v-belt drive without using an idler. And the idler should always be positioned on the "slack" side if possible. Yes, it's possible to run a toothed-belt without an idler as very little "stretching" takes place.

Take a look at the Corvette Central catalog on the "engine belt" page 77. It clearly shows an idler being used on big blocks but it's showing the idler on the tension side and also pushing against the belt rather than pulling it outward. That method is acceptable for slow speed and small loading applications but it will cause undue heat and stress on the belt's cords. Personally I think that illustration has been drawn wrong because it's also showing the alternator being driven off the power steering pump pulley "daisy chain style"; something I have never seen G.M. (or anyone else) do.

Correctly routed the alternator belt goes around the middle groove of the water pump and crankshaft pulleys, the power steering pump is driven off a 3/8" wide "add on" pulley that is bolted to the front of the 3-groove crankshaft pulley, and the A/C is driven off the front groove of the 3-groove water pump pulley......................
 
#25 ·
I'm the 3rd owner. The first guy had everything done at the dealer, the second owner bought it from him in 1971, and was a next door neighbor. I've been with it since '71 thru all three engines and everything that's been done all of it's life since 71, and it's never had an idler.
 
#28 ·
Idler Pulleys Used On Big Blocks

I finally made it home-- And a picture from the 69 AIM for you..


With A/C you get an idler. No A/C, you don't get one..

Corvette Central says the idler used on the non A/C cars pushed against the back side of the belt rather than pulling it outward. So the idler would have a flat side; not a V groove............................
 
#31 ·
If you would like one I'll make it and ship it to you for a total of $175. I hate to charge that much but it takes me around 6-7 hours to make one.

It would come to you complete with the pulley, mount bracket, cam adjustment, belt, and even the three bolts to mount it.

Or, I can send you the drawings and part numbers so you can make your own...........................
 
#33 ·
I am running a big block and decided to get rid of the whole factory belt/pulley debacle. I went with a serpentine single belt system and I am very pleased with the results. I went with a high SCFM electric fan and a 4 core aluminum radiator to keep it cool with the A/C running. The factory set up was prone to throw belts and smoke belts anyway. No smog pump needed.
 
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