Currently my vacum advacne is disconnected on my truck. I do not think it was working before and I need to modify the line to hook up to my new Holley. I took it out on the road with no advance and it was fine. There was no pinging, the engine ran great. My question is, do I need to get the advance hooked up ASAP? Or will I be fine temporaily? Also Ive heard that you can get adjustable vacum advace units, where can I get them? I called autozone for a adjustable for my 66 and they said it didnt exist. Anyhow I thought it was intersting how it was not pinging or anything with no advacne.


Any help would be greatly appericated.


FERacing66

 

Hey FERacer

Check out this web site was a lot of help for me. I don't think you need to worry about hurting anything with it disconected but it will help performance to get it right.

http://www.fordmuscle.com/archives/2...ng/index.shtml

jd

 

a friend of mine told me to leave the vacuum advance plugged. i guess with it hooked up it helps with economy. but he prefers to plug his off.

 

pinging occurs when the timing is too far advanced. with no vacum advance you are only running 5-10btdc at all rpms instead of up to 35-40btdc at high rpms. but this will not hurt anything, just rob power

 

here's a little story, this friend of mine(bowtie fan) always insists on setting his timing at 35degrees advanced at idle on his malibu. well his dad use to drag a 55 belair and that's where he always set his timing and he was unbeatable. well that belair did not have any kind of timing advance. it could barely run at idle, but run like a top at high rpms. the malibu has vaccum advance. so with his 35 degree advance at idle goes to who knows probblay 70 degrees at high rpm. he didn't understand why he'd run 19 and 20 second 1/4 mile. then i set his timing to factory specs without him knowing, he lost all traction at launch, and ran a 13.6

 

Thanks for the help guess im fine for now.

 

Vacuum advance has no effect on your timing at full throttle. It is only used to advance timing at part throttle for better mileage. If you hook it to your manifold it will also advance the timing at idle but if it is hooked to your ported fitting on the carb then it only works at part throttle.

 

Good info. I try to explain it to people that way but everyone thinks I'm full of BS.

 

Well Rusty, all they have to do is drive around with a vacuum guage hooked up and they can prove us right or wrong. If you are pulling vacuum at full throttle you have a carb that is way too small or you are revving the engine way beyond sanity.

When you get down to it all a carburetor is just a big vacuum leak controlled with an air valve, a metered fuel supply and a right foot.

Diesel engines pull no vacuum becasue they have no throttle blades. The manifold is open and the power output is controlled by fuel supply.

 

what would be the best total advance for a 352 in a 66F100 used for daly driver and towing a basboat ( maby 3000 lbs max ) ?

 

around 36 degrees total initall close to 20

 

I agree with the above for total. If you can get away with that much initial then go fer it. You will need to have the distributor re-curved to get the right amont in both places. I set my initial as high as I can without putting excessive load on the starter with the engine hot. I then set my total for the most power possible. You will also have to change springs to get the curve right. Stock springs won't give you full advance until you are almost over-revved. I set my advance to come on as fast as possible without creating spark-knock.

This in my opinion is best for any build from stock to serious HP.

 

So would that be 36 with the vacume advance factored in ? or would it be best to get rid of the vac advance alltogether? and you would want this total at what RPM ? 2500 ? so I would need to set the distro to 8 to get the 16 dagrees and use light springs to get total advance to 36 by 2500 rpm and set the inital timing to 20 dagrees BTDC, is this correct ? and this will be ok for towing also ?

 

Your most likely wanting full advance somewere between 2500 and 3000.
yes set dist to 8 to get the 16.
yes inital timing to 20.
It all takes a bit of playing around you might find your initall setting works best at 18 or 16. The amout of advance in the dist might not easly be reduced to 8 to get the 16. So you have to ballance it out.
I would recomend finding a copy of Jacob's Electronics book on ignition systems. It has a lot of info and explanes a bunch of things becides ignition systems and how to tune/evaluate your ignition system.

As for vacuum advance. I f you dont have a properly working EGR to reduce your combustion temperatures at cruse (which is when vacuum adv is used)
your best off with out it.
I wount even begin to tell you all the crap I went through vacuum gages, hoses little tweeker valves, in the car adj them while driving ... shims, tweeking the unit with a allen wrench etc. test driving I have done trying to get the vacuum advance to work on older engines with out EGR. The results didnt get me the economy back that was lost disconecting the vacuum adv unit. In the end I was lucky to acheve 1 MPG or less and was right on the verge of detonation or was depending on the last fuel I purchased , weather conditions , terain, how much I was halling etc.

One thing that is fairly consistant your engine temperature seems to run its lowest with the timing set curved etc at its optimum. If you make any changes and the engine seems to run a bunce hotter back off and investigate what you have done.

 

One more question. My truck has overdrive so it cruses at 65mph at 2150 RPM. do I still want to have the mech advance comein at around 2500 ? wouldnt that mean i will never get full advance at freeway speeds ?