So I am putting the small block back in the kid's car and for some reason we misplaced the belts and the cards with the part numbers on them. We had trouble for some reason getting the right ones last time. It was an A/C car but not installed. I am not 100% sure it has all the correct brackets even. Alternator is on drivers side. Has power steering. Any idea on which to start with as far as lengths or part numbers from oreilly's? Thanks!

 

Try looking the belts up on Rock Auto's web site. They should have a variety of manufacturer's belts so you can use whichever manufacturer your local parts store carries.

 

Will do thx!

 

I'm building up a '72 small block engine right now and I'm test fitting all the accessories and brackets before installing into the car. I have an AC car (but don't have the compressor yet) and found that the Gates #7450 fit the power steering pulley and Gates #7560 fit the alternator pulley. Rock Auto listed Gates #7550 for the alternator but it was too short to slide onto the pulley. The #7450 is 45-5/8" long, the #7560 is 56-5/8" long.

 

I have found it necessary to go one or two sizes smaller that the recommended due to belt stretch. That is US made Dayco and Napa/Gates belts. Something has changed in rubber make up and the belts stretch a lot.

 

Olds307:

I was frustrated when I searched for the correct belts for my car. Rock Auto and other auto parts stores listed 2 or 3 lengths for each application without any description to know which length was correct. So I measured the belt lengths by wrapping a short section of 1/2" diameter rope around the pulleys and measuring the length. With the Gates part numbers I listed earlier, the alternator and ps pump have about 40% of adjustment left when tight; I should be able to compensate for belt stretch over time.

Rodney

 

I just stumbled onto why my no AC alternator belt continually stretched and eventually broke. I have an old 455 performer on my car and apparently the manifold bolt hole is slightly misplaced making for alt ( or AC) misalignment if you can actually get the bolt in the hole.

I would guess the stamped alt brackets allowed the ham fisted mechanic ( me) to flex the bracket enough to line up the bolt whereas the cast AC brackets don't flex making it more of an issue.

Anyways after reading up on it I loosened that intake bolt and sure enough my alt was under tension allowing the pulley to be in the right fore/aft location but somewhat angled creating premature belt wear.

Bracket r n r is on today's list of things to do

 

RetroRanger:
I hear ya on the brackets puzzle. I have aluminum heads, headers & Edelbrock intake manifold on my '72 350...none of these aftermarket parts exactly match the OEM parts. I've had to bend, clearance, and open up holes to get everything to line up properly on the drivers side brackets. I don't have an AC compressor yet so I haven't tweaked anything on the passenger side of the car, but expect much of the same massaging will be needed to mount the compressor.

I used a framing square (straight edge) laid against the crank pulley and then measured to the ps pump and alt. pulleys to make sure they were in the same plane and not angling forward. It didn't take much work but definitely more of an art than a science to get things to line up. Make sure you have the correct spacers on the water pump and the lower block mount. I had to clearance the alt. bracket that mounted on top of the intake and grind down the mounting boss because it was just a little bit too high. The power steering pump needed a washer between the pump face and the bracket at the adjustment slot to get it correct in the vertical plane. After several hours of fussing with it, I'm happy with the belt alignment and everything easily moves through the full adjustment range. I wish you luck with yours.

Rodney

 

THKS Rodney

I've actually been driving like that for 2 yrs but the belt wear made me reexamine the set up, it's real close w all the correct spacers etc, but the alt pulley is slightly less than parrell to the belt

 

Olds belt set up can become a nightmare with any changes in water pumps or brackets removed and spacers lost or put in the wrong places. I find, unless I have about 3/4 of the adjustment, the belt will stretch enough that it will not be tight enough. This has been on 3 Olds powered vehicles. I also had my Dayco serpentine belt stretch enough that it started squealing. I also had to tighten the multi rib belts on my daughter's Toyota Tercel at least once. I do have a high RPM squeal on the 70S, it needs more tension on the alt belt. It could be a slight misalignment or the chrome pulley as well. I call it a victory when the belts stay on, I have had the belts blow off any time I revved the motor on a couple of Olds V8's, that is when an alignment issue really shows up.