[dave65FB]

i am running a carbed 5.0 in my 65 mustang. it has a roller cam so i used a rebuilt distributor for a 85 carbed 5.0. it came with a vacuum advance. i still have to dial in the carb and timing, but when i hook up the vacuum advance to a port on the carb or to the intake manifold, it drives really rough, bogging a lot when i accelerate. when its not connected at all, it runs a lot better but still has a little hesitation when i first take off or at high rpm. what do you guys think the problem is?

 

[windsoreight]

The vacuum to the dist. should be a ported vacuum. There should be no vacuum at idle. It should pregress as the r.p.m. is raised. You might have it hooked up to the wrong vacuum port. Did you set base timing with the vacuum removed?

 

[dave65FB]

i assumed that i should wait until i hook up the vacuum to set the base timing. what port should i use. i used one directly from one of the runners on the pack of my performer rpm air gap intake and that didnt work well, nor did the one port on the side of my 600 double pumper. what port should i use?

 

[393Clevor]

find the port on the carb that has no vacuum at idle. When you start to accl the vacuum should go up.

 

[dragman64]

I like manifold vacuum better.

 

[dave65FB]

i tried both, the only two ports on the carb and one on the intake and all ran crappy. accelerating was like a bunch of tiny back fires with a loss of power. after unplugging and leaving the distributor without vacuum, it ran pretty nice. but top end seemed a little rough, but it could just be the sound of the xpipe at high rpm thats making me think its running funny.

 

[musthave302]

The only way to know for sure what is going on with timing really is too see what you have initial, total, and when you have all the timing in. I don't have too much experience with stock duraspark stuff, but with aftermarket distributors w/ no vacuum advance, generally, total advance should probably be 32-34 total, with all of the timing coming in i believe by say 3000-3500 rpm. the easiest way to check this is with a fancy timing light that has a dial on the back. You set the timing to 34, rev 'er up, and move the distributor until the mark is showing on zero. The dial on the back retards the light flash the approriate amount of degrees, and makes it a cinch. They cost a bit though. You might be able to acheive desirable results with no vacuum advance, and light springs. Hope that helps. Of course, your timing marks could be off too, but don't know how to check that with motor assembled.

 

[Mattstang65]

There is a really good article on "timing" and how to set it in the Fordmuscle archives. Proper timing will make a world of difference on how your car performs!