So I playing around with more vacuum lines and i decided to experiment with the vacuum advance since I had a wicked hesitation from a stop. I switched from ported carb vacuum to manifold vacuum. Wow what a difference. Much better street manners now. Im yet to see what kind of fuel economy effects i get but the whole nature of the engine has changed. After dialing in the idle speed and mixture it sounds more like my neibors 427 camaro now when it idles. Sometimes i wonder if this thing has a mild cam. The heads cant be flowing any better than stock cause its still slow as a dog but I gotta saying im loving the pushrod torque. Im still used to ohc engines.
Depends on where you have timing set. Looks likee you can advance your timing with vacumn hooked proper. You gotta watch pre-ignition! To get the best out this, you need to play with timing an recurve your dizzy. All depends on engine build. Keep track of all you do an record findings. This is where dynos are great
If you had a difference with the change in vacuum source, sounds to me like you had the timing retarded too far to start with. I run all mine with ported vacuum. I set the initial timing at 12-14* BTDC. With the desrciption you gave on how it idles now, you could also have a vacuum leak.
to add details, im close to 15" vacuum right now, when the advance was hooked to ported vacuum it was maybe 7 or 8. Im not getting pre-ignition that i can detect. I dont think i have a vacuum leak... unless maybe there is one from the carb... i dont have enough experience to tell but the ported vacuum is very weak at idle and rises pretty well under light throttle. I didnt check this with a gauge tho, just a quick finger check. After driving to work and back I still wanna play with some things, my fast idle certainly needs to be set, and my idle speed is far to high right now... like 1200 or so i think. I guess i wasnt at full temp when i set it, foolish mistake. I have a new concern tho, i've known there was a shimmy in the crank pullys and at first i thought it was just worn belts or something but i got under and checked and behind the pulleys, something is wobbling about 1/2" Im guessing the damper is FUBAR.
If the damper is wobbling that bad, chances are the timing's screwed up as well. Ported vaccum should be zero at idle, and only reading when the throttle's opened. 1200 rpm is way to fast for idle. What carb do you have ? You need to set the initial timing first, then the idle speed, then fine tune the idle with the mixture screws.
Your timing is off if you can run manifold vacuum on the distributor. You are advancing the timing at idle instead of the opposite with the line hooked proper. You need to advance your initial timing. That will give you the torque you are missing now with the line hooked proper. The distributor gets ported vacuum. Period. That is how it's made to work, if you have to advance the timing with manifold vac, it is a problem, not something to brag that you found a better way. Put the line back to the proper port and figure out what's wrong. You are currently retarding the timing when it should be advanced, and advancing it when the design is to retard it.
Also, make sure the outer ring hasn't slipped on the balancer. That might be why you have it timed severely retarded and don't realize it.
Agreed, Our distributors are curved to be used with ported vacuum. All you did was advance your timing more at idle, which is why your idle speed is now too high. Also, your complete advance will be coming in too early, and even of you can't hear pre-ignition, it may be there.
