MustangWorks.com : Ford Forums - View Single Post - Vacuum advance still far too aggressive after crane adj unit

crazypete · 01-11-2003, 10:28 AM

I know I posted on this before, but I wanna throw this out to the community before I finally decide to scrap the system and cap it off. I could use that extra 1-2 mpg, even though I'm getting 20 mpg with a carb and 3.73's (I have no idea either!)

I'm using an 85 mustang distributor with a holley 670 street avenger. I get 20 hg's vacuum at idle (1100 rpms, but same happens at 800 rpms), I'm not running egr or air pump and I have no spacers or anything else in the way. Based on how smooth it runs, I do not have a vacuum leak. Running base timing for now : 10 deg. Yes, I am using the spark advance port on the carb =) . Mixture guage shows stoich + 1 bar.

Originally, what was happening is that, with the light aimed at the timing marks, I would connect the vacuum advance at IDLE and see the marks shoot off to somewhere under the motor and it would run like crap and backfire immediatley when I touch the throttle lever by hand. Holley said it misdrilled it's spark ports on some of the avengers and they sent me a tested unit under warranty.

Ok, now, at idle, no problem. I hook it up and see no change. Cool, I think. I reach over and blip the throttle. BANG!! BANG!!! I can feel the backfire go up into the carb. I see the timing marks jump way up to just past 40. Darn it.

Ok, I get the crane cams adjustable cannister and allen wrench it all the way out. Same behaviour. I allen wrench it all the way in. Same behaviour. This is so annoying! What is going on with this silly car?

01-11-2003, 10:28 AM	#1
crazypete Registered Member Join Date: Sep 2002 Location: Boston Posts: 592	Vacuum advance still far too aggressive after crane adj unit I know I posted on this before, but I wanna throw this out to the community before I finally decide to scrap the system and cap it off. I could use that extra 1-2 mpg, even though I'm getting 20 mpg with a carb and 3.73's (I have no idea either!) I'm using an 85 mustang distributor with a holley 670 street avenger. I get 20 hg's vacuum at idle (1100 rpms, but same happens at 800 rpms), I'm not running egr or air pump and I have no spacers or anything else in the way. Based on how smooth it runs, I do not have a vacuum leak. Running base timing for now : 10 deg. Yes, I am using the spark advance port on the carb =) . Mixture guage shows stoich + 1 bar. Originally, what was happening is that, with the light aimed at the timing marks, I would connect the vacuum advance at IDLE and see the marks shoot off to somewhere under the motor and it would run like crap and backfire immediatley when I touch the throttle lever by hand. Holley said it misdrilled it's spark ports on some of the avengers and they sent me a tested unit under warranty. Ok, now, at idle, no problem. I hook it up and see no change. Cool, I think. I reach over and blip the throttle. BANG!! BANG!!! I can feel the backfire go up into the carb. I see the timing marks jump way up to just past 40. Darn it. Ok, I get the crane cams adjustable cannister and allen wrench it all the way out. Same behaviour. I allen wrench it all the way in. Same behaviour. This is so annoying! What is going on with this silly car? __________________ 91 GT Carb conversion, holley 600 double pumper, edelbrock performer intake, FMS "C" drop springs, march 1000 underdrive pullies, crane 1.7 roller rockers, GT-40P headers, bassani x pipe, american thunder catback, FMS 4.56's, msd aL6, trunkmount battery, A/C eliminator kit, 3000 stall tci streetfighter, AOD with transgo kit, A+ servo, 300M hardened lockup shaft, kevlar bands and 28,000 gvw trans cooler, 3 core radiator, 300 lbs stripped with a full interior