need help 72 big block
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Joined: Aug 2000
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From: lilburn ga 30047
need help 72 big block
I need a belt configuration diagram or picture for a 72 454 with ac,ps,and air(smog pump). Assy manual doesn't .show. Also is an idler pulley necessary on this set up please help
1967 Pedal Car Champion
Joined: Mar 2020
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From: US-PNW
Strange that that AIM illustration shows the main crank to water pump belt going around the idler pulley. All illustrations I've seen showing the A/C idler have it pressing against the belt from the outside rather than inside the belt loop.
Last edited by barkingrats; Oct 29, 2020 at 11:55 PM.
Le Mans Master
Joined: Jun 2006
Posts: 6,393
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From: Tampa Florida
Yes, the idler pulley (454's with AC) is necessary so you can tighten the belt if or when is stretches.
Without that belt, everything is relying on the power steering belt.
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Old Pro Solo Guy
Joined: Dec 2017
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From: Marlton NJ
Excellent info!
From what I could gather on the history of the 72s, the LS5 as planned originally for 72 had no air pump and the LS6 did. But then they didn't pass emission certifications, and California's were different anyway. My 72 AIM shows things at that step. Then at a very late date before production the LS6 was cancelled completely for 72, (presumably for failing emissions) and the LS5 grew an air pump. The LS6 deletion apparently just made the AIM but the LS5 air pump did not make the corrections. IIRC even the air pump equipped LS5 was banned in Cali that year. Not sure if that was because it didn't pass the second time or they just didn't go thru it again for only 1 state. Parts books are strange as well in this area.
GM was really struggling with this new-fangled emissions compliance back then!
From what I could gather on the history of the 72s, the LS5 as planned originally for 72 had no air pump and the LS6 did. But then they didn't pass emission certifications, and California's were different anyway. My 72 AIM shows things at that step. Then at a very late date before production the LS6 was cancelled completely for 72, (presumably for failing emissions) and the LS5 grew an air pump. The LS6 deletion apparently just made the AIM but the LS5 air pump did not make the corrections. IIRC even the air pump equipped LS5 was banned in Cali that year. Not sure if that was because it didn't pass the second time or they just didn't go thru it again for only 1 state. Parts books are strange as well in this area.
GM was really struggling with this new-fangled emissions compliance back then!