[Guest]

I think I just... yeah, I think I just had a thought. Would it be possible (and accurate) to test how much vacuum advance I am getting by using something to hold the mechanical advance weights in place (maybe thin grade wire), and then using my timing light to test what vacuum advance I am getting while goosing the throttle? If so, how much vacuum advance should I adjust for? Right now I have it at one turn with the hex wrench.
Thanks

69 Royal Maroon Convertable
2001 GT Bullitt on order

 

[Jim]

Why not use a hand held vacuum pump? They don't cost that much and you can get a steady state condition from them.

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[camachinist]

hmmm....now wouldn't it be possible to take a total advance reading at, say, 2500 rpm or so with the vacuum advance hooked up....note the reading, then disconnect the vacuum advance and repeat? The difference in readings should indicate how much vacuum advance the engine is seeing at a high velocity, low load situation, which is where vacuum advance is highest...

Most distributors have all their advance in by 2500-3000 rpm...

If you wanted to graph the results, do the same tests and idle, 1000 rpm and up in 200-500 rpm increments....

And your interest in this is?

Pat
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[Guest]

That would be to easy, I guess. I don't see why the above idea wouldn't work - right? How much total vacuum advance should I adjust for?

69 Royal Maroon Convertable
2001 GT Bullitt on order

 

[Guest]

Hey Pat,
That makes sense. Is there any recommended amount of vacuum advance I should be getting at say, 3,000 RPM, and at 1,000 RPM?
Thanks for the reply.


69 Royal Maroon Convertable
2001 GT Bullitt on order

 

[camachinist]

To be honest, I've never checked...*G*

Only timing I check on the D-coder is the idle advance...with the vacuum advance hose disconnected

Race car...run it up to 6K rpm, set the timing at 34 degrees and go racing...

Maybe an untapped area of performance I've been missing??

Pat
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[Guest]

Hey, I don't know. I'm just trying to fine tune everything. I guess I won't worry about the vacuum advance!

69 Royal Maroon Convertable
2001 GT Bullitt on order

 

[Guest]

It's not really scientific or anything, but where I've noticed the biggest impact of vacuum advance is when you're lifting off the gas at speed(like to go around a corner or something). The throttle plates are closed (causing high vacuum) and the engine is in a lean condition from the closed plates so a fair amount of extra advance is needed. You'll often hear race cars or others that don't run vacuum advance pop-pop-popping out the tailpipe in this situation. I just dial in some vacuum and put the hammer down then back off and see how the engine responds. Crane recommends changes in 2 turn of the allen key increments and once the car decelerates smoothly with no popping or surging I'm done.I hope this helps

.......Bill

 

[Guest]

Bill, thanks for the great info. I noticed that popping noise before I replaced my vacuum advance unit. I don't have the popping noise anymore, so I guess it is adjusted right.

69 Royal Maroon Convertable
2001 GT Bullitt on order

 

[mstngjoe]

The accurate setting of vacuum advance is more a seat of
the pants thing than a given amount. It really needs to be
adjusted while under load in increments such as is mentioned
above. For a great article on timing, checkout the archives
at FORDMUSCLE.COM. Look in the tech area for "Timing is
Everything". Good luck.

65 FB "J" 302 lots of mods. 94 GT K&N only.
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