Old Air Products Underdash Slimline Air conditioner??

[sargentrs]

The purpose of vacuum advance is to advance your timing under load conditions (high vacuum situations). That typically occurs when you're going uphill under low rpm's or towing. You're probably familiar with "clattering" in those situations and 'punching it' makes the clattering stop by giving her the extra oopmph to get up the hill. The vacuum advance mechanism automatically advances your timing to compensate in those situations.

[69SCJ]

Yes, the vac advance will help gas mileage.

When their is no to low load on the motor, such as cruising at 55 mph, the vac advance advances the dizzy considerably. You don't get pinging because it's a no load situation. As soon as you floor it to pass somebody vacuum drops and the dizzy reverts back to mostly or all mechanical advance.

I don't think it's uncommon to get up into the 50's BTDC under no load situations.

Hope that helps,
Tyler

[69SCJ]

Sorry, didn't see Sargents post since it was on the next page.

I see our explanations conflict each other. More advance causes pinging so I'm pretty confident my explanation is correct. That said, I'm comfortable with eating crow if need be.

[sargentrs]

http://www.460ford.com/forum/showthread.php?t=117504 I find crow tasty if seasoned properly. I may have misspoken somewhat. My apologies for any confusion. I do believe in running v/a however it works.

[flyboy2610]

Is there any way to get A/C without giving up the glove box?

Yes, there is. Buy an aftermarket AC only system. You will keep the original glove box that way.
I bought the Old Air Products Slimline inside unit several years ago, and do actually plan to install it eventually!
http://www.oldairproducts.com/catalog/1 ... -4501.html
(It just seems like things I should do before that keep coming up, and then the budget and work schedule conspire against getting those things done!)
You can also buy this as a complete system:
http://www.oldairproducts.com/catalog/1 ... -4362.html
This is the system that jamesrtw referred to in the original post.
From what I've seen of my unit, I like it.