i have a 750 eddy on my 440.my vacum advance is hooked to the open port below the butterfly. should i hook it to the timed port. what will that change? for a stock motor where should my timing be set? thanks

i say you want it on the ported vacuum (timed) because if its below the butterfly, the vacuum will be changing from idle in neutral to idle in gear which will change the advance which will change the idle which will drive you nuts

There's a reason they make the ported vaccuum nipple, just for distributors.

theres 2 nipples on the carb

I would use ported & set the total(vac adv disconnected) at 38 & see where that puts your idle timing at & if that amount is enough for your particular cam for it to idle decent. For your curve if it is not pinging(too fast a curve) no damage is being done only that there would be more power to be had by a faster curve.

i,m lost dis conect the advance and set timing at 38' at what rpm, what would timing at idle be. not shure i understand how the system works pretty new at it

you would raise the rpm up until it wont advance any higher which may be above 3000 rpm then turn the dist until you show 38 degrees & you would need a dial back light or a timing tape or a remarked timing marks to see where 38 degrees is at then lock the dist down THEN let it go back to idle & see where your idle timing is at(vac adv plugged for all of this) EDIT you would need your initial to fall between ~5-15 btdc & maybe back off your total from 38 if need be but see what you have 1st.

Read the latest mopar mag explanation as to why to run your advance from ported, not direct vacuum. Steve Dulcich is the author.

Absolutely correct! You got it.
That 50-55 is right about what you want for cruise conditions (gives best economy and throttle response)
And yes, you step on it, and the total advance will very rapidly drop back to your initial-plus-centrifugal amount.

what did you end up with at idle???

check it at idle with the port connected and disconnected (and plugged at the carb)

real good info so far. so does the allen screw in the diaphram limit/max vacum or mechanical advance

turning the allen wrench in the vac can makes the can require more vacuum(or less depending on which way your turn the allen wrench) to overcome the spring tension & add advance. The amt of adv(in dist degrees) is stamped on the arm(which is inside the dist when its mounted). You can file the stops to add more adv that the can can provide or use paper clips or something similar to reduce its travel to reduce the amt of advance. & different cans give different amounts of adv that they can add & that # will be stamped on the arm. Vacuum adv is a very good economy aid & should be dialed in AFTER you have your initial & your mechanical curve dialed in.

EV2Cuda,

Can you post the mopar magazine article about running ported vs manifold vacuum? I saw acouple of mopar mags yesterday but couldn't find the article. Thank you.

George

Neither is wrong. Both offer additional advance above the mechanical and initial timing.

The ONLY difference between ported and manifold is you will have advance during idle and light throttle cruise conditions with manifold vacuum. Most engines need more timing at idle and using your starter as the gauge is wrong. You can also close your throttle blades more with more ignition timing at idle.

I've spend 2 years recording tank after tank in my truck. Ported and manifold have no effect on mileage. I'm sure it's better than without but my numbers show no improvement against each other. I did have tighten the carb idle speed screw with ported but had more torque just off idle with manifold. I have a manual trans. Not sure if this would be noticeable in an auto.

just wondering is vacum high or low under a load with rpm around1700. i don't diesel or start hard and like my of idle torque and response cruising. i get spark nock under a load say if i lug it in 3rd or 4th. if i stay on the gas the knock goes away as the r's go up.if i hold 3rd to about 2300 and hit it theres no hesitation and it screams.if i retard the initial it boggy down low. its a relatively stock 440 in my 4x4. any sugestion. if it was my 2 stroke banshee i'd just plug it into my computer and adjust my timing curve. i don't no if a small engine 2 stroke guy should mess with a bb mopar.lol