Thank you David and Ron for sharing this. There is a lot of good basic info in this from Chilton. Chilton usually has excellent tune-up and emission controls (including the engine control computer) sections. I often found Chilton manuals about the best for these topics among the repair manuals available in auto parts stores.
One interesting detail in here is look at the plug gap specs for 1975-76. see how GM spec'ed 60 thousandths for most everything those 2 years then started shrinking that spec in 1977. '75 was the first year for HEI electronic ignition--GM must have been real confident in that system at first, then lowered the gap spec in the 3rd year...
Wonder why? HEI is an excellent OEM system, though the aftermarket has done significant improvements over the years. I don't know the story here but that spec change jumps out at me... I do remember Dr Christopher Jacobs (Jacobs Ignition, now gone) had some things to say about this very thing in his ignition guide book. Might have to dig that book out to see If there is something worth sharing here...Never hurts to re-read stuff like this!
I think it's a great idea for anyone trying to learn about engines to at least read some of these old manuals to get a good foundation of knowledge.
TracyG Gadgetman Reno
