should i run without vacuum advance?

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1969dodgedartgt

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Hey all noob question time....
It sounds like my car is misfiring at about 3000RPM and above, but if I pull my vacuum advance I dont hear any misfire. I'm soon to have a new intake and carb but in the meantime.... can I just run with no advance??? or how should I try to adjust my timing to cure this? set timing back?
ty
 
If it runs better without the vacuum advance, leave it off (make sure you plug the port that it is getting vacuum from).

With that said…… I would still check your timing and see where it is and what it's doing.
 
I was checking the timing thats how i found out it doesnt misfire without the advance. Thanks

i'll go test drive without. I was just reeving while sitting
 
The vacuum advance pod has a linkage inside the distributor that connects to the plate that houses the reluctor (little black cube) or back in the old days the points and condenser. When the advance linkage tries to turn the plate and if the guides are worn out it will misalign the reluctor and give you a miss. Take a look inside and check that the plate is not loose.
 
I'd definitely say shes happier without... just beat that girl hard, sounds great on freeway. pretty sure I just broke my speed record, to bad I didnt have my gps or replace my broken speedo to verify. plenty of potential and durability in that little 318...

I'll look in distributor tomorrow or soon.

i think i know what you mean by nfg.. no good...
when I did my tune-up a month ago I checked that it was moving with vacuum.
another part to put on the grocery list....
for now, what works for her works for me.

Thanks for help
 
If it seems to run better with the vacuum advance disconnected, that is not your signal that you should run without the vacuum advance -- it's your signal that you need to do some diagnosis and adjustment or repair. Many things can cause this what you are seeing. Base ignition timing too far advanced, broken or detached mechanical advance spring, worn point plate (or pickup plate). Running without the vacuum advance costs you performance, driveability, and fuel economy, so disconnecting it to eliminate the misfire being caused by something broken or out of adjustment is a get-by band-aid at best.
 
It will most-always have that "miss" when you rev-it ....with no load. But out on the road it should not miss at all. Vac-adv helps MPG ..big time. And you can TUNE THAT to your application.
 
Yup, as others have pointed out, the vacuum advance isn't something that you should simply disconnect to solve a problem. ESPECIALLY on a street car. As Dan pointed out, it will cost both performance as well as MPG, regardless of what others may argue. Some say it has nothing to do with performance, but part throttle accelleration will certainly be effected since part throttle is where the vacuum advance comes in. The hard reality is that the factories got it a lot closer to right than a hot rodder really wants to admit. It is difficult to improve all the way around on what the factories designed.
 
1968FormulaS340 said:
If it runs better without the vacuum advance, leave it off (make sure you plug the port that it is getting vacuum from).

With that said…… I would still check your timing and see where it is and what it's doing.
Click to expand...

An engine will run "better" for a short time without a harmonic balancer, but you don't yank it off for the hell of it.
 
make sure that the vacuum is properly ported , too . it's connected to the Air Horn portion of the carb , at least on BBD Carter 2 Bbl's .
 
StrokerScamp said:
An engine will run "better" for a short time without a harmonic balancer, but you don't yank it off for the hell of it.
Click to expand...

No.

When I said…….. "With that said…… I would still check your timing and see where it is and what it's doing."

It was the lazy way of saying what slantsixdan said in post #7.
 
yes I'm viewing this as a band aid. the engineers who designed these things sure knew more about what they were doing than I :p

I'm pretty sure timing is not the prob, I played with the timing a bit, I'll play some more. I be giving the inside of the distr. a hard look and maybe some bad words... haha

I maybe seeking to repair/replace plates in there. enough talking from me about this until I do some more about it.

I'll say again, she seems very happy I put a band-aid on her. I'll watch mpg if I let this go that long.
 
I've found that even my mildly built 318 likes to have a LOT of initial timing. I'm not sure why, but it runs best with around 18 to 20 degrees of initial timing. Now, that's a lot more than the stock spec. So, when the vacuum advance kicks in, on top of the mechanical advance, it's too much timing (think like 40+ degrees of advance).

I tuned my mechanical advance to put me at about 35* of advance, all in, and run without the vacuum advance. I know several small block mopar guys that run their cars like this, and one in particular whose opinion I would trust more than anyone else.

I would still suggest that you check out your initial timing to see what you're at, and check the limits of the mechanical advance, since you may have another problem. But, if your initial timing is advanced much beyond the 12* mark, you may be over timing it with the vacuum advance. The vacuum advance is adjustable, but with enough initial timing you won't be able to set it low enough.
 
LH23H2R said:
make sure that the vacuum is properly ported , too . it's connected to the Air Horn portion of the carb , at least on BBD Carter 2 Bbl's .
Click to expand...

You do have to make sure the vacuum advance is connected to the correct vacuum nipple, yes, but no, it's not on the air horn of a Carter BBD (or any other Mopar carburetor I can think of, which is a fair good variety of them). The vacuum advance port on a BBD is on the starboard side of the main body casting, which is above the throttle body and below the air horn castings.
 
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