new member
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
Check the emission label and you should find its GM# 360420 with code AS. This will indicate your A.I.R. configuration. Engine code CHB is called out for an L48 M40 with federal emissions. It was configured with A.I.R. pump GM# 7801149. Also look at your exhaust manifolds and you may find plugs where the tubes where connected. 
There's always been debate if the L48 w/ the M40 had A.I.R. or C.C.S. The TIM&JG states no A.I.R. for this specific combination, but many question it.
In '75, the A.I.R. pump did not push the air into manifold trees in the exhaust manifolds, but through a single 3/4" pipe into the passenger-side exhaust.
Also, it seems very likely that there were three A.I.R. pumps used throughout the model year. The 7817575 pump (7801149 backing plate) would be correct from November of '74 to/through April of '75. There's evidence that '74 pumps were used up at the beginning of the '75 run, and in April of '75 they switched to the '76 pump. I am working to get this edit into the next TIM&JG.
