The Dodge Challenger Message Board

I have setup my Timing on my 383 Engine
Initial timing at Idle is 12 Degrees
Without vacuum hose fitted between carb and distr. Timing is set to 35 Degrees at 3500 rpm
and with vacuum hose fitted the Timing is 52 Degrees at 3500 rpm.

My problem:
If I slowly increase the rpm from Idle and up When I reach 4000 rpm the engine start to go rough and when I increase even more the engine start to bang in the exhaust system. (If I flash the engine hard from Idle up to 5500 rpm I don´t have any problem)

but if I do the same without the vacuum hose fitted between the carb and the distb. I doesn´t have the problem to go slowly from Idle and up to 5500 rpm then the engine goes great.

my distributor is a orginal 1969 383 with electronic ignition, I don´t find that I have any adjustment in the vacuum clock on my distributor.

I know that the vacuum adv. is only for fuel save and to burn the fuel better in crusing speed

What to do??

Quick fix would be to just dissconnect and plug the vacuum and live without it.

Another choice would be to physically limit the amount the vacuum can advance to around 10 degrees. Wrap some wire around the "arm" from the vacuum can and solder it in place so that it can only move a little.

Hi Dave
I have disconnected the vacuum hose line, I think the Engine will work much better witout it.

I limited my vacuum can to about 11 degrees and it worked very well. I just changed to a MSD mechanical though which does not use a vacuum advance at all.

I will also change it to a MSD in the future, but now I just disconnect the vacuum and drive the car without vacuum connected to the distributor.

You can sometimes adjust the vacuum advance by using a small allen wrench through the vacuum advance hole where the hose hooks up. You could also do a little junk yard digging and find one w/less advance. The advance is usually imprinted on the v/advance cannister. I hope this helps.

Tom

I have already dissconnect the vacuum to the distributor, i will drive my car without vacuum adv.
I don´t have any adj. in my v/advance cannister, I don´t know if there are several different typ of v/advance cannister my is a 1969 orginal 383 v/advance cannister.
But I will go without the vacuum adv. until I change it to MSD ignition.

72challengerorange was saying that the adjustment is through the hole that the hose hooks up to, its not on the advance mechanism itself, so you wont see anything on the outside.

I'm not sure you missed this, I imagine its hard to get all the information out of a mechanical explanation when its in a different language.

I know how to adjust a adv. canister it is true the hose hole with a 3/32 Allen wrench but my canister does not have that adjustment.
//Roland

hey guys. i need to revive this thread. i dont have any pressing "problems" with my car, but a few questions and concerns.

since i haven't posted anything in quite a long time, i have a lime green 74 with a 360 and automatic. mild cam with a MP distributor. i read last week that dave and a few others agreed that initial timing should be around 16-18 degrees w/o vacuum. with vacuum and at 2000 rpm it should be no more than mid thirties.

well, me and my dad checked mine and it was at 36 initial and in the 50's at 2000 rpm.

we tried to turn it down to the teens and it didn't run to good. we turned it back up and i think im in the mid to high 20s now. i cant tell much difference except for it idles a bit rough. it might not be so rough if i turned the idle screw up. it still starts fine, so there are no problems about that. it does appear that its running a bit hotter though. the main reason i wanted to check it and hopefully adjust it is b/c under 2800 rpm it really has no power. i mean, it does alright, but the amount of power difference below approx 2800 and above is quite dramatic.

what are the current thoughts on this subject?

Those readings cannot be right. The engine could not even start above 10-20 degrees initial (it would kick back on the starter) and above 35 degrees it would be "pinking" like mad.

Take the vacuum off the dizzy first of all. You cannot measure timing with the vacuum on. Plug it so there is no air leak to the carb.

14-18 degrees initial is all you want. The factory setting is only a couple of degrees.

The way to find your best initial is to keep advancing until the engine just starts to kick back. Then back off two degrees.
This lets the engine run cooler and there will be less smell from the exhaust.

Then from there you want no more than 35 degrees at 3000rpm an no more advance at all after that rpm. You want half of that advance in by 2000rpm.

This usually means modifying the timing curve and advance total in the distrubutor.
So if your initial was 15 and your total 35 that means the distrubutor has to be limited to 20 degrees advance and your 2000rpm timing would be 25 degrees.

Only after all that can you attach the vacuum line. The vacuum would have to be limited in effect though. if you are pushing the limits on the timing like this it is probably better to leave the vacuum out.

dang dave, thats a lot of info. well i will try to check my marks and timing light and all that stuff, but im pretty confident those were the numbers. disregarding what i have now, i'll check on TDC and try to get my stuff situated. hopefully it will get done this coming weekend. i'll keep you posted. thanks again for the advice.

by the way, even though i've not been talking a bunch, i've been keeping up w/ the posts. I hope your health continues to improve as my prayers are with you.

so yeah, we'll see what happens and i'll let ya know.