340 disributor education

[Madmaxx]

ok having some issues put on a new carb and have jetted it up... but I still have an issue with light throttle tip in  if you are off the gas completely then return to light throttle  there is a hesitation..if you get into the throttle med throttle its almost not noticeable..put this car on another car it ran great no issues...so i'm looking to the timing/distributor...no vac advance hooked up...with cap off I can see both plates but both a solid  no movement?...where is the mechanical advance?  under the plate?..72 cuda 340 looks like factory elect ignition with a msd box under dash...what am I missing here..thanks

[cudabob496]

seems like a carb issue, not distributor.
sounds like just need to increase size of accelerator pump squirter nozzles.
what kinda carb?

[Madmaxx]

I thought so too..edelbrock 600...but I have jetted up, changed springs moved accel pump shot..with no change...I was beginning to wonder if the weights weren't draggin or hanging up..i put this carb on one of my other cars that's more radical than this basically stck 340 and it works good no issues whatso ever?  no sure where else to turn? 

[Chryco Psycho]

Yes the mechanical weights are under the upper plate , the dist in the picture is points , having a broken sprin or too light springs can cause weird reaction off throttle etc

[Madmaxx]

well I feel like a total idiot!!!!..lol..had I looked at my own pic I woulda seen the points staring me right in the face!!..argh...well don't I feel dumb!!.I was more concerned with the weights/plates...I notice the upper plate and the lower plate do not move..is this the norm?...well I need to start shopping for electronic ignition!!..I will be pulling it out soon !

[jimynick]

If the plate that's connected to the vacumn advance doesn't move, you may have found a problem- no spark advance. Point ignition isn't THAT bad a system; after all, they ran internal combustion engines for nearly 100 years before the electronics came in. That's not to say the electronic ones aren't overall better, they are, but you can run a 340 on points up to about 6500 rpm before they start to bounce. Look at it as a poor mans rev limiter. 

[Madmaxx]

hey thanks for the replies!...ok I pulled the distr out ,pulled the vac off and took out the plates  shot it up with wd40 seems pretty smooth working ..I did notice it has a big spring and a smaller spring on the weights.(maybe someone has been in here before?)..I assume I have to reinstall the vac adv?  it would seem that it acts like a return spring of sorts on the moving adv plate. I'm not planning on using the vac adv ..I did notice the vac adv has very little distance of movement?..remember i'm not used to mopars!..lol  i'm learning...I will eventually upgrade to electronic..but for now I want to get it running good as I can with what I have..i appreciate the education i'm receiving...I also removed the mouse turds in distr.  I really don't even want to know how they got there..lol I assume this is a junkyard pc...so that's what I know so far!

[Madmaxx]

ok learning as we go.assembled everything..the vac adv will not move when vac applied I put 30 in. to it never moved..but it does move..not very easily but I can move it..not sure how much pressure to move it..compared (sorry) to a gm distr I can move with a little pressure..this one requires way more to move it..hench the plate requires that as well for mech adv...installed, put timing at 8 intitial still has hesitation..moved to 10 still there...i'm still thinking it not able to move the adv freely enough to get what it needs?..i might just head to one of the box stores for a new adv just to have something to compare to?

[Cuda54]

I did not think that MSD would work with points. I thought MSD only worked with the electronic distributers.

[Chryco Psycho]

there is an allen screw inside the nipple of the vacuum advance it may have been screwed all the way out to prevent the plate moving , I do this all the time . Really though you do not want vacuum advance to work , if you rotate the shaft you should be able to see the mechanical weights under the plate , they should move freely & usually aloow approx. a 20* curve so setting the intial at 16* you should have total of 36* with RPM , perfect

[Madmaxx]

i'm not sure this thing will start with 16 initial..i'm at 10 and it seems to drag the starter...maybe I will move it up to see...i'm a little confused tho..so the plate that the vac ad is connected to this doesn't control the advance for both vac and mech.?  I have always thought that plate was moved by vac ad. and the weights ?..if I can hardly move the plate it would seem the weights would have a hard time doing so?.man this is quite the education!! been doing this stuff for a long time..but have never been this far in the distr..let alone a mopar one... thanks for taking the time to educate me!

[cudabob496]

i'm not sure this thing will start with 16 initial..i'm at 10 and it seems to drag the starter...maybe I will move it up to see...i'm a little confused tho..so the plate that the vac ad is connected to this doesn't control the advance for both vac and mech.?  I have always thought that plate was moved by vac ad. and the weights ?..if I can hardly move the plate it would seem the weights would have a hard time doing so?.man this is quite the education!! been doing this stuff for a long time..but have never been this far in the distr..let alone a mopar one... thanks for taking the time to educate me!

starter dragging? engine grounded well? weak battery. I'm at about 17 degree intitial advance. I put a switch before my ECU. With switch open, start engine
cranking, then flip switch, and starts right up. Its like having timing retard at startup.

[Madmaxx]

hey cudabob, I guess maybe dragging isn't the right term..starting hard maybe..grounds and battery are good..well I will try to put in more intial and see what happens..to me it just seems that to move the advance plate in the distr..takes way to much effort. but if the weights advance it without moving the plate then this is a non issue.?..thanks for the help...and I need lots of it! lol

[Madmaxx]

ok, I gave it 16 initial..to my amazement it seems to start when warmed up..so we'll go with that for now..unfortunately didn't solve the original problem i'm chasing....so for now I will drive it..i would like to do an ignition upgrade this winter..i have had great service from pertronix conversions on my gm and amc stuff? we'll see...I will probably head back to the carb to chase the hesitation issue..altho I put this carb on a another car and was just fine no issue...this is the symptom...has a hesitation when  driving and off throttle then ease back in it stumbles hesitates what ever..if you give it more throttle than light there isn't any stumble..if you are off and on quickly no stumble..longer you coast off the throttle bigger the stumble when easing back in?...I figured I would do the best I could to eliminate what I can....from what I can tell the ignition seems ok?  thanks for the input!