bhaas

I set my timing to 32 BTDC without the vac adv hooked up and drove the car. It ran awesome. When I hook the vac adv up it adds about 23 deg. I hooked it up to non ported just to see what it was at idle with a timing light and it was at about 35 - 36. Initial is 13 and the car runs killer. No more bog. So, do I really need vac adv? My canister isn't adjustable either. I know if I hook it up it will ping and knock like crazy. I could only run 6 deg initial with it hooked up and it would ping a little at times. Now it doesn't do it at all. And runs better. Thanks.

Brad...

Riley's35089rs+

For a daily driver? Yes.... I'm surprised you can get it to idle.

ede

that'd be 55* of timing, i don't think a SBC would run with that, i odn't think it'd even start at your base setting. lot of drag cars don't run vacumn advance just full mechanical

82camaro

The extra advance you get at part throttle at lower rpms crusing down the highway will keeps the plugs nice and clean and make the engine more efficient(better mileage). Other than that, no you don't need it. A better solution is to go with an adjustable unit so you can tune the vacuum advance down. So, no you don't need vacuum advance, but it does have advantages if you keep it.

bhaas

Right on. Well here's what I'm gonna do. I'll run it for a week like this, with no adv and check my plugs and see what they look like. I also adjusted my carb till I got max vacuum on my gauge at 900 rpm's, 15" is all I could get. I richened it up a bit. That's the most vacuum I could get out of it. I guess I can live with that. I had two nice wet spots from my mufflers on the ground. Might be a tad rich. But the throttle response is killer.

Brad...

F-BIRD'88

The adjustable vacuum advance is like $21 from Jegs.
On a race car or a boat you don't need it 'cause they are either
idleing or under load.
On a street car you cruise around at part throttle/ high vacuum
most of the time. The Air/fuel ratio is leaner during this time.
The proper additional vacuum advance added to the
initial and mechanical advance is nessessary for proper combustion timing.
Lean(cruise) mixtures at low density take longer to burn
than richer (power) high density(WOT) mixtures and need this extra (vacuum advance).
Benefits are better gas mileage better drivability, cooler cylinder walls and combustion chambers, cleaner plugs and LONGER ENGINE LIFE!!!!
Not to mention your header gaskets will always develop leaks
from unburned/late burned fuel overheating the headers.
A car motor needs about 40 to55 deg advance at cruise/ high vacuum.
So you need to add and additional 10 to 15 deg
with vacuum advance. The $21 or so you spend now will pay you back many times over down the road.

If you want to be really thrifty why not just remove your vacuum advance canister, flip it over and block (limit) the travel of the arm by half
and reinstall it. Now you have a 12 deg vaccuum can.
Pretty easy eh......

http://www.jegs.com/cgi-bin/ncommerc...29&prmenbr=361