any one useing msd box with a vacuum advance

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fstfish66

fstfish66

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just looking for ideas,,,i currently use a MSD blower boost box ,,compatable to the msd 6 i would guess,,and a advance control box with a msd dizzy with no vacuum advance,,,

i dont race the car,, i street drive it to local cruise nights and shows,,,im thinking i may be able to increase my gas mileage,,from 4 1/2 too ????? by going to a vacuum advance dizzy,,,just wondering if any one is running a msd advance box with a vacuum dizzy,,before i call msd and see what they have to say,,,,any opinions would be great,or if any one has switced back to a vacuum advance,,,,
 
I think the quick and easy way might simply be to run an adjustable timing ciontroller with your current system so you can dial in more advance when you can make use of it safely (at cruise). The down side is it isn't self regulating. So you'll have to dial it back every time you slow down or need to get on it harder. What does the engine pull for vacuum while cruising around now?
 
I'm not up on that MSD box but running a vacuum advance on a street car is going to get you mileage.
 
If you're running a roots blower, which I think you are judging by the picture and the fact that you are running a boost controller, I would stay away from running any vacuum advance. As far as mileage is concerned, a big roots and dual quads really isn't the way to go as technically, you are always under boost. I'll bet that car hauls *** though. :)

Vacuum may always be present due to the roots sucking away under the carbs regardless of throttle position and you may end up toasting some pistons. Attach a long hose to one of the carb taps and run a vacuum gauge in the passenger compartment and let us know what you see. I'm curious as heck to see what readings you get at idle, cruise and part throttle acceleration.
 
I suspect it would improve things a good bit. Taking the time to really get the ignition curve dialed in can make for huge gains in mileage. As Ramcharger mentioned, however, you're always going to have a little bit of vacuum with a blower manifold since the boost retard and blower are getting their signals from different points, so you will need to pull a little base timing to compensate.
 
thanks for all the input,,, it is not at constant boost,, boost doesnt appear till im in it hard,,it makes 13 psi,, but pump gas 93 octane is only good for 9 psi ,,with out a modern tuner type computer,,ill look again but i think at part throttle its sitting at 10 pounds of vacuum,, i have a dual guage vacuum/booost,,

the msd booost retard only pulls the timing back when it starts making boost,, the msd boost retard didnt come with any info,,,but on jegs or summit it talkes about the boost retard specs,,it is currently set to retard 1 degree for every 3 pounds of boost,,

the guy that did my carbs,,genius,, insists to disconnect the booost retard,, he says there pron to fail,,, but im not in it that hard,,,like he said when he set up the carbs leave it at 13 psi,,, by the time you see 13 psi on the street your probably in some ones trunk,,,lol
i ordered a cable from MSD for the msd box to a mopar perf vacuum dizzy,,msd doesnt make a dizzy with a vacuum for a mopar,,at least the only ones thay make are self contained with a ecu in the cap,,,

so i have a mopar dizzy,, im going to try it,, msd says i may loose a little bit of throttle responce,,,but il gane 4 to 5 miles to the gallon around town,,and thats what im looking for,,,just cant use the dash controled advance box,,,,

its just a cruise nite car,,no one chalenges me if they pull up next to me on the street any way,,lol thanks alll sorry for being so long winded
 
Sounds like the guy that set the carbs may not understand the retard function... Everything fails at some point...lol. I dont know how the vacuum advance will work on yours... so maybe try but be careful? lol
 
I seriously doubt you will nearly double your curent mpg with just VA, I'm in nearly the same situation , Have you double checked where your pv's are coming in at? sounds to me like they are coming in during cruise Are they Boost refrenced? and to where makes a diff on a blower depending on the cam my intake vacume is 10" @ crusie but at the carb adaptor it's 16" so you see my point on the PV's I run x2 EPS 1405's and have an 8" springs for the pv's and run both sets of secondary jets @ 120{ super rich under boost} untill I went and opened up the primary jetting I was getting 11 mpg under cruise , point is I run as lean as I can under crusie But as rich as I can under boost{ 5 psi @ 9.8-1 comp} But When I drop the comp to 8.0-8.2- 1 I will be able to drop the total jetting @ spring rates quiet a bit and mileage should only get better, point is: I would check your PV's{ actualy check them with vacume guage for there advertised vacume rate alot them are no where even close to whats stamped on them" once verified adjust your advance to be all in @ or near your cruise RPM and adjust your jetting to be as lean as the engine can stand{ watch for overheating} and MPG will shoot up substatialy,
as i'm sure you are aware that blown engines for the street with some sort of mileage expectation the entire combo needs to be setup for that , gearing convertor tire size like any other vehicle, also with 33"{what i run your look about the same" tall tire you will want a gear in the 4.30 may be even 3.73 range to be able to get into 3rd gear @ crusie and not have it be unresponsive on need to be into boost to have any low end~
Did this help or make things worse as I was kind thinking about our situations together and not specificly just yours.
 
yup i am running 33 inch tall tires currently 4.56 gears,,in forth the final drive ratio is 3.89 i cruise at 2850 RPM at 60 MPH... going with a 3.91, which wil drop my cruising RPM by 600 rpm,,probably wont hurt my out of the hole a bunch,, i have a 3.09 first gear,,,

these carbs are done right,,a blower motor needs fuel,,like you said in a lean condition over heating is only one problem,,next is crack cylinder walls,,,
im not sure where my total mechanical advance comes in at, but ill take note of the vacuum at differnt speeds before i switch to the vacuum dizzy for the experiment,, i have 2 holly 650s that now flow 862 each,,im not trying to kill a holew lot of performance just get a little more out of a gallon of gas on the local cruising,,,

my orignal question was more about if any one was running a MSD box with a mopar electronic vacuum dizzy,,, now that i have the proper plug from MSD,, after carlisle i will give it a try,,and let you all know what i came up with,,,,if i picked up any mileage,, or if i lost a ton of throttle responce,,,
 
My thought was the retard allows the carbs to be a little leaner and make more power safely when under boost. If you have that retard box I'd re-install it along with the vacuum can and see if it helps too.
 
Out of curiousity,how fast is that fish of yours?
Ever ran it down the quarter?

The thing looks vicious!
 
thanks i tried to make a pass one night,,a few years back,,was a cool fall night,,,i had regular hoosier quick time tires at that time,,and a weak fuel system,, moisture comming out of the track like mad,,spining the tires in first second and third gear,,ill have to dig up the time slip,,the 60 foot time was quick if i remember,,but by the time it hooked up in third gear and started making boost,,i didnt have enough fuel it leaned out banged the gasket out from under the blower,,at that time i had 2 stock 650 cfm carbs,,those carbs now flow 862 each,,with a slight up grade to the fuel system,,it may be enough to make a pass on a cool day,,

the car went 12.8 @ 110 mph,, spinning the tires and blowing the gasket out from under the blower,,my guess with a good set of slicks,and big enough fuel system high 10s...thanks for asking
 
Anytime!

When ya can,that would be good to do!
Put nice tires on there an take it again!

Love the car man,it screams tough.
 
nemesis said:
Anytime!

When ya can,that would be good to do!
Put nice tires on there an take it again!

Love the car man,it screams tough.
Click to expand...

heres what i have never used lol

chryslers@carlisle 2009 day 2&3 141.jpg


chryslers@carlisle 2009 day 2&3 142.jpg
 
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