|
Vacuum advance or not???
#1476774
07/31/13 01:44 AM
07/31/13 01:44 AM
|
Joined: Dec 2011
Posts: 257
Way North Idaho
1KoolBee
OP
enthusiast
|
OP
enthusiast
Joined: Dec 2011
Posts: 257
Way North Idaho
|
First off thanks to all who have helped me with my engine build so far. Its coming together slowly, but I'm almost there. Trying to decide if there is a benefit to running a vacuum advance on my street/strip motor. Its 500 cubes, 11.2 static compression, MP .557 cam, 1.6 rockers, Eddie Heads, sixpack induction, 4-speed trans. should I stick to straight mechanical advance, or is there a good reason to keep vacuum advance?
'68 Bee 383/TF/Factory Air...high school sweetheart
'67 GTX Clone project,500 six pack,Hemi4-speed,Dana
05 Dodge Viper, 505 V-10, 6-speed Tremec
|
|
|
Re: Vacuum advance or not???
[Re: 67_Satellite]
#1476777
07/31/13 08:39 AM
07/31/13 08:39 AM
|
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
|
Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
|
Quote:
What fuel? At that compression probably better than standard pump swill. If it doesn't ping, run it to manifold vacuum.It will give you the extra timing for a better idle/mileage and automatically goes away under heavy/full throttle. 
my build is close to the OP, even the 11.2:1, I run 38* all in by 2200 and NO vac advance. But I also run meth/H2O injection to reduce detonation. A tad OT but how do yo uhave the 6-pack set-up?
|
|
|
Re: Vacuum advance or not???
[Re: 1KoolBee]
#1476778
07/31/13 08:50 AM
07/31/13 08:50 AM
|
Joined: May 2004
Posts: 12,386
Taxes & Virus's R-US, NY
Dragula
I Live Here
|
I Live Here
Joined: May 2004
Posts: 12,386
Taxes & Virus's R-US, NY
|
Absolutely not...Too inconsistant...And as for mileage. I did a test on one of my street/strip vehicles, and I think that is a wives tale. If you have a cam more geared for racing than stock, it will never happen.
On mine I did the mileage check back to back one week with a distributer without vacuum advance, and the next week a distributer with vacuum advance. If I saw .4mpg difference it was a lot....Since it had a small 11g tank, and my drive to work is almost 30 miles I typically put fuel in it every day and checked the mileage...11mpg without, 11.4 with it...and it didn't always get the extra mileage...yippy....less then 1/2mpg on one of the five days, saving the world now. It even ran better without it.
Last edited by Dragula; 07/31/13 09:08 AM.
|
|
|
Re: Vacuum advance or not???
[Re: 1KoolBee]
#1476780
07/31/13 10:51 AM
07/31/13 10:51 AM
|
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
Taking time off to work on my car
|
Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
|
Quote:
... is there a good reason to keep vacuum advance?
Yes, but the carb & distirbutor have to be tuned to work together to see the benefits.
A typical factory vacuum advance setup and standard "quick" mechanical ignition curve are generally a recipe for over-advancing a performance engine under high vacuum conditions.
Done right, better idle and fuel consumption. Done wrong, detonation from too much ignition lead under part-throttle use.
Even on my Challenger (mid-10 second street/strip car), if I could find a good distributor w/ fully tuneable vacuum advance (amount of advance x vacuum level) & mechanical curves, I'd like to run one. I think there's something out there that would work, the new Crane electronic distributors, but they're not cheap.
|
|
|
Re: Vacuum advance or not???
[Re: 1KoolBee]
#1476781
07/31/13 10:59 AM
07/31/13 10:59 AM
|
Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
|
master
Joined: Oct 2003
Posts: 7,506
Az
|
Quote:
First off thanks to all who have helped me with my engine build so far. Its coming together slowly, but I'm almost there. Trying to decide if there is a benefit to running a vacuum advance on my street/strip motor. Its 500 cubes, 11.2 static compression, MP .557 cam, 1.6 rockers, Eddie Heads, sixpack induction, 4-speed trans. should I stick to straight mechanical advance, or is there a good reason to keep vacuum advance?
Your set up leans more to race than street operation so it's a tough call. If you are going to drive a lot of street miles, it might save you a little in fuel costs to use it. With that cam, you would want to run ported vacuum for idle stability and you would probably have to recurve the distributor accordingly. 
Fastest 300
|
|
|
Re: Vacuum advance or not???
[Re: BradH]
#1476785
07/31/13 10:01 PM
07/31/13 10:01 PM
|
Joined: Dec 2011
Posts: 257
Way North Idaho
1KoolBee
OP
enthusiast
|
OP
enthusiast
Joined: Dec 2011
Posts: 257
Way North Idaho
|
Quote:
Quote:
... is there a good reason to keep vacuum advance?
"if I could find a good distributor w/ fully tuneable vacuum advance (amount of advance x vacuum level) & mechanical curves, I'd like to run one."
Earlier today I was checking out the MSD 6AL-2 Programmable (6530)...interestingly enough it has several advance and retard curve features including one that works off a MAP sensor (vacuum or boost). Also burnout, Launch, and Max RPM limiters. All tunes with a laptop, so you could probably have different pump gas and race gas timing curves? not cheap, ~$350, but I need an ignition box anyway. Maybe "electronic" vacuum advance control? hmmmmmmmm......... 
'68 Bee 383/TF/Factory Air...high school sweetheart
'67 GTX Clone project,500 six pack,Hemi4-speed,Dana
05 Dodge Viper, 505 V-10, 6-speed Tremec
|
|
|
Re: Vacuum advance or not???
[Re: Thumperdart]
#1476787
08/01/13 01:15 AM
08/01/13 01:15 AM
|
Joined: Dec 2011
Posts: 257
Way North Idaho
1KoolBee
OP
enthusiast
|
OP
enthusiast
Joined: Dec 2011
Posts: 257
Way North Idaho
|
LOL...Yeah you're probably right Dom! Keep it simple is a good creed to stick to.
'68 Bee 383/TF/Factory Air...high school sweetheart
'67 GTX Clone project,500 six pack,Hemi4-speed,Dana
05 Dodge Viper, 505 V-10, 6-speed Tremec
|
|
|
Re: Vacuum advance or not???
[Re: 1KoolBee]
#1476788
08/01/13 01:38 AM
08/01/13 01:38 AM
|
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
Quote:
LOL...Yeah you're probably right Dom! Keep it simple is a good creed to stick to.
If you drive ALOT on the street the advance is well
worth the time to figure it out... even at .5 more
miles per gal... its just a balancing act between the
carb and the dist... whats the max timing it will
take at that amount of load.. when I get the time I
will be running a mech advance along with vac advance
just to get the mileage up.. right now I just have
mech advance
|
|
|
Re: Vacuum advance or not???
[Re: Thumperdart]
#1476790
08/01/13 02:03 AM
08/01/13 02:03 AM
|
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
Quote:
Quote:
LOL...Yeah you're probably right Dom! Keep it simple is a good creed to stick to.
It`s all good man but these are musclecars and the extra mpg`s can`t hurt but just seem minute to me w/the hastles of the balancing act that`s needed to make it work. Good luck either way man............ 
You do know all it is is sticking a allen wrench in
the vac port on the vac can and turning in less or more
per given load(usually set for cruise load).. some
times it takes a delay valve in the vac line
|
|
|
|
|
it!
plus vac. adv. is for wussy cars NOT muscle cars.............. 