...how many of you run mechanical advance dizzys on the street. I've only run va*** advance dizzys but I got a smokin deal on a Mallory Unilite Mechanical Advance. The motor will be pretty cammed up with a little but of head work as well. Should be around 10.5:1 compression, 4bbl, etc. The motor isn't anywhere near ready to drop the dizzy so I still have time to change. Pro's/Con's please. Many thanks.
i ran one for a while and didn't like it, it was an accel dual point. the engine would kind of bog until it hit around 2-2500 rpm then pick up. the points might have just been slightly out of adjustment too. i like my vacuum advance unit better. just my experience
I run an Taylor Vertex wanna be electronic dist. with mechanical advance in a roller cammed 10.3 aluminum head sbc and I have no complaints. I also had the occasion to try three distributers in another sbc that I had in an engine test stand. I tried the electronic Taylor Vertex look a like mentioned above, I tried a Mallory unilite and a points GM dist. Out of the three, the Mallory started the best, literally as soon as you hit the key. The Taylor and the GM points dist cranked over just a bit before firing. My $.02
I used to run one on a drag car with a 4 speed and it worked good.It also didnt need any low rpm responce.
ive run one on a sbc with a tri-carb for the last 6 years, had no problems with it at all - all been good.
ALL of my cars run strictly mechanical advance. I am much more concerned with knocking the tops out of the rod bearings at high r.p.m. than a little bit of off the line performance. But with a solid roller 455 olds, it's pretty hard to want more "off the line".
That's just a tuning issue more than a problem inherent to the design. You should have re-sprung the advance mechanism a little softer to get the timing to come in a little sooner. The MSD's I've got came with like half a dozen sets of springs and three or four different fly weights, so they're pretty tunable. Dunno much about the Accel's, but I'd imagine if Accel didn't make a kit, you could come up with a modification on your own.
Unless you are talking about a full race distributor that is locked out, most all have some sort of mechanical advance. The vacuum pot on the side of a "vacuum advance" distributor pulls in additional advance only under low load/high vacuum conditions for improved mileage.
btmatt is right, Billy. I'd use a vacuum unit on the street for better manners. Better idle, and better mileage when cruising. Dial in the mechanical part for best performance, though (lighter springs, relieved weights). Then you have the best of both worlds.
always used vacuum evern on street/strip cars, all automatics, Ive been told with a manual trans you can get away with a mechanical
I have allways been told that as a rule of thumb you should run a mechanical on any motor with more than one carb. Something about the vacuum signal can get muddy with multiple carbs. Tune (weights and springs) the mechainical and you shouldn't have any problems at all.
put a used (new in 1985) unlite with mech. advance in my 32 back in 1992 and have not had one single problem.
I run a Mallory twin point mechanical advance dissy on a sbc, with no problems. It's the second one I've had and the other was good too. Both single 4 barrel mild sbc's with autos. I was wondering about the pros and cons of vacuum versus mechanical for my current project as I've got both types and wondered if one was better. It's an LA Chrysler smallblock, and all the cars from the factory seem to be vacuum and the mechanical dissy came from a marine engine.
The car won't run any better with or without it but part throttle and cruising you would have better mileage. Big concern as mentioned is the advance curve, how much and how fast.
The unit I have in my 289 now is a GM style HEI. Va*** advance with a mechanical centrifugal advance as well. I tuned that curve to be pretty decent I think. I would have no problem tuning this one either. I was mainly wondering if the off-idle lack of advance that you would get from a va*** advance would be enough to make me regret it. The car will have a manual behind it thus leaving the stall speed up to me and with the cam I'm running, I'd probably stall high enough not to notice the lack of va*** advance. I just need to pay more attention the the advance curve when setting it up. I think I'll run this one for now and if I hate it, its not hard to change, after all its a SBF.
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