Thank you all for the great responses, lots of good knowledge around here. Makes sense of and lines up with this 1100 page service manual from GM.
Slow to respond, busy weeks and spent time on the truck doing an oil change and working on some electrical (the stuff I'm really good at). Need to get a timing gun still before I can check all that out. Turns out neither autozone or o'reilly have any to loan out.
That aside, a couple more follow up questions.
Quote:
Originally Posted by geezer#99
8* might be stock but you should be able to advance that up closer to 12 to 14. I live at the same elevation and weather as you do and run all my stuff at 14 initial.
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Quote:
Originally Posted by MikeB
I agree that 12-14 degrees will probably be the sweet spot, maybe even 16. The symptoms of too much advance are:
-- pre-ignition (knocking) on acceleration, especially when engine coolant is up to temp
-- engine turns over slowly when you're trying to start it
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How exactly do I tell I've advanced it far enough though? I understand the physics/chemistry/thermodynamics behind the timing and such, but how do I tell where between 8* and 16* is best? Or is there no way short of a dynamometer?
Quote:
Originally Posted by geezer#99
Could you also post a pick of your engine bay.
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The fat lady is certainly not pretty, but she sings beautifully. I've attached a few shots under the hood.
Quote:
Originally Posted by Dead Parrot
Is your truck still covered under any kind of emissions testing/inspections?
Verify that the following still work:
Exhaust heat riser valve
THERMAC system
EGR(if equipped)
PVC system, PVC valve and filter are cheap
Both mechanical and vacuum advance
If they are several years old or age unknown, consider new cap, rotor, plug wires and plugs. While the cap is off, repair or replace any broken advance parts as needed.
Replace any cracked or hard vacuum hoses.
Sounds like a lot but if you do your "how to" research first, then buy or borrow any needed tools should take less then a day to fully check things out.
Trying to tune an engine when these systems are not working properly is an exercise in frustration.
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About that... that A.I.R. pump may or may not be working, but for a couple weeks it was making all sorts of noise (sounded like something rotating was striking something stationary on each revolution).
I'm free from emissions checks here, so I'm contemplating removing the A.I.R. pump in lieu of replacing it. I posted a different thread
here about the issue, but it didn't get any responses. Everything else you've mentioned is in condition worth leaving for now. A lot of maintenance was done not long before we acquired the truck--new alternator (I guess my all original claim is a bit false), new radiator hoses, fresh battery, fresh spark plugs. The plug wires/rotor/cap aren't brand new, but they aren't original either.
In case anyone is curious about the full state of it all, there are a handful of small things I'm working on with the truck too. A small coolant leak, some excessive/poorly routed wiring to be reassessed, new windshield washer system needs to be purchased, rear quarter fender that came w/ needs to be installed (we'll do that after the engine/electrical are tip-top), horn's not working (something after the relay I think), cruise isn't working (though I think I fixed it last night and just didn't know how to activate it, ...trim-down used to be a thing apparently), and the cold air intake snorkel--if you can call it that--is AWOL.