Vacuum advance

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Vacuum advance

Post  quick 52 on April 25th 2015, 6:18 pm

I have a mild 472 in a 52 F1 truck... Been wanting to get better mpg right now its around 8 in the city a 12 on the Hi way ... So I was looking at the vacuum advance and seem that the diaphragm is blown is the much to gain by replacing it... The truck is a cruiser that I do race a few times a year... The timing is 23 initial and 34 total being all in at 2700 rpm was thinking that a adjustable vacuum advance with around 10*.... Most of my cruising rpm are low from 1500 to 2000 50mph to 70 mph running a overdrive trans

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Re: Vacuum advance

Post  DFI429 on April 25th 2015, 6:26 pm

Not sure I totally follow, but 23-34 is a pretty tight curve, so with vac advance I'm not sure you'd see any difference.  If the diaphragm is in fact 'blown', you'd be ahead by at least plugging the leak.
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Re: Vacuum advance

Post  quick 52 on April 25th 2015, 7:27 pm

DFI429 wrote:Not sure I totally follow, but 23-34 is a pretty tight curve, so with vac advance I'm not sure you'd see any difference.  If the diaphragm is in fact 'blown', you'd be ahead by at least plugging the leak.
Have plugged the vacuum port with a cap... The curve is pretty tight but with the cam i'm running it likes the timing up and run its best times with a total of 34. Was thinking that at low rpm and load a increase of timing may help with mph

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Re: Vacuum advance

Post  supervel45 on April 25th 2015, 9:28 pm

You could stick an adjustable vacuum advance on it and see if it helps. It won't cost that much, and if you don't like it plug it off. I would check it with a timing light, and keep watch for preignition and detonation.

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Re: Vacuum advance

Post  quick 52 on April 25th 2015, 10:09 pm

supervel45 wrote:You could stick an adjustable vacuum advance on it and see if it helps. It won't cost that much, and if you don't like it plug it off. I would check it with a timing light, and keep watch for preignition and detonation.
Kind of what I was thinking look up a adjustable vacuum advance canister on summit and crane make one... the one that is on there now is accel the dizzy is one also but is a ford duraspark...

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Re: Vacuum advance

Post  FalconEh on April 25th 2015, 11:35 pm

Does it look like this?, if it does you you can have it, it worked fine on my stuff, you can swap it out use it for parts whatever N/C send me a pm if you want it, I believe it is from a 74
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Re: Vacuum advance

Post  rmcomprandy on April 26th 2015, 10:18 am

quick 52 wrote:  I have a mild 472 in a 52 F1 truck... Been wanting to get better mpg right now its around 8 in the city a 12 on the Hi way ... So I was looking at the vacuum advance and seem that the diaphragm is blown is the much to gain by replacing it... The truck is a cruiser that I do race a few times a year... The timing is 23 initial and 34 total being all in at 2700 rpm was thinking that a adjustable vacuum advance with around 10*.... Most of my cruising rpm are low from 1500 to 2000 50mph to 70 mph running a overdrive trans  

Unless it has lower compression ... you will only gain part throttle "tip-in" detonation, which is not a good thing.

Slow down the mechanical advance curve so it isn't "all in" until after 3,800 RPM and your mileage will increase with the vacuum advance; wide open throttle acceleration will decrease slightly.

You can NOT get everything so choose your priority.

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Re: Vacuum advance

Post  quick 52 on April 26th 2015, 12:54 pm

rmcomprandy wrote:
quick 52 wrote:  I have a mild 472 in a 52 F1 truck... Been wanting to get better mpg right now its around 8 in the city a 12 on the Hi way ... So I was looking at the vacuum advance and seem that the diaphragm is blown is the much to gain by replacing it... The truck is a cruiser that I do race a few times a year... The timing is 23 initial and 34 total being all in at 2700 rpm was thinking that a adjustable vacuum advance with around 10*.... Most of my cruising rpm are low from 1500 to 2000 50mph to 70 mph running a overdrive trans  

Unless it has lower compression ... you will only gain part throttle "tip-in" detonation, which is not a good thing.

Slow down the mechanical advance curve so it isn't "all in" until after 3,800 RPM and your mileage will increase with the vacuum advance; wide open throttle acceleration will decrease slightly.

You can NOT get everything so choose your priority.
I do want the best of both worlds... So maybe I will try with the 3 step retard box and set timing up around 40* total for cruising then pull 6* out when it come to the track which may only be a few times this year

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Re: Vacuum advance

Post  supervel45 on April 26th 2015, 1:28 pm

http://www.msdignition.com/Products/RPM/Timing_Controls/Timing_Controls/8680_-_Adjustable_Timing_Control.aspx Here's an old school way. I used it when I wanted to spray nitrous as it was fast easy and inconspicious. Like Randy said if you have high compression be carefull. I kind of doubt you will gain much in MPG, in fact you may loose some depending on your driving habbits.

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Re: Vacuum advance

Post  quick 52 on April 26th 2015, 3:36 pm

I do spray when at the track and if they are running no et a little to quick no bar rule they get pissed if you put down a mid 10 second pass... I use a 3 step retard box with a dual stage plate system activate with a wot switch plus a couple digi-set timers... I leave with 50hp and stage in 125hp about 7 tenths out pulling 4* on first and 6* second

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Re: Vacuum advance

Post  supervel45 on April 26th 2015, 4:52 pm

quick 52 wrote:
rmcomprandy wrote:
quick 52 wrote:  I have a mild 472 in a 52 F1 truck... Been wanting to get better mpg right now its around 8 in the city a 12 on the Hi way ... So I was looking at the vacuum advance and seem that the diaphragm is blown is the much to gain by replacing it... The truck is a cruiser that I do race a few times a year... The timing is 23 initial and 34 total being all in at 2700 rpm was thinking that a adjustable vacuum advance with around 10*.... Most of my cruising rpm are low from 1500 to 2000 50mph to 70 mph running a overdrive trans  

Unless it has lower compression ... you will only gain part throttle "tip-in" detonation, which is not a good thing.

Slow down the mechanical advance curve so it isn't "all in" until after 3,800 RPM and your mileage will increase with the vacuum advance; wide open throttle acceleration will decrease slightly.

You can NOT get everything so choose your priority.
I do want the best of both worlds... So maybe I will try with the 3 step retard box and set timing up around 40* total for cruising then pull 6* out when it come to the track which may only be a few times this year
If you want to stay electronic, give it a try. One thing I do know is my small block fuel injected trucks with overdrive are only getting 2-3mpg better mileage on the highway, so you are not doing to bad for a big engine.

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