mopar performance distributor question

[69wannabe]

I am currently running a 493 ci engine in my charger with dish diamond pistons, comp 285 extreme energy cam,rpm intake and 850 double pump carb. Got cast iron 346 heads on it with 214/181 valves and mild port work and shaved 20 thousands off the bottom of the heads so my compression should be around 9.9 just guessing. I and running a mopar distributor with a chrome box and I cant run my timing over 11 BTDC. I used to run it on 14 BTDC before I swapped in the stroker kit. Just wondered if anyone knows what these distributors mechanical advance is. I have ran it up to 3000 rpms and checked it and its pushing 34 BTDC which is good I guess. It is just more prone to pinging now when I try to pull the timing up a little higher than 11 BTDC. Its runs fine where its at so that may just be the way the ball bounces. It is a little more responsive when the timing is on 13 but when I start stretching it out on the highway I can hear it pinging slightly so back down to 11 it goes. Just wondered if any one else has any experiance working with these distributors. I can see an adjustment for the advance but I dont want to make a mess and get the distributor out of adjustment when it runs pretty good now. Thanks

[charger500rt71]

A little more info needed. What octane gas? Vaccum advance hooked up or plugged? Stock springs in distributor? Did you degree cam?

[Cooter]

One thing to remember about strokers is the more you pull that piston down in the cylinder, the more compression you will have. I'm thinking more like 11.0:1 with iron heads WILL NOT LIVE ON pump fuel premium. I've tried. I have an iron head 440 with like 10.8:1 and will not start when hot.


Good luck, but I think you will have to swap to aluminum heads.

[471_Magnum]

Need to limit the mechanical advance. Recurve for about 16 mechanical. Then you can run about 18 initial and it will really come to life.

Have to shorten the slots in the distributor to do this. Can be done by welding, brazing, or some cut up washers and JBWeld.

Should have asked this first, but what vintage MP distributor?

[69wannabe]

Its a later model MP distributor with the adjustable advance. I dont run a vacumm advance and the springs are whatever came in the distributor and I am running 93 octane in it always. The pistons are diamond dish and are supposed to be 9.8 to one with 86cc heads so I don't think i'm pushing over 10 to one. May do some playing with it and limit the advance so I can pull it up to 14 or 15 degrees and see how it likes that. If I could get 14 and no pinging out of it I would be happy!! I am running cooler plugs in it too. The J12's were too hot I guess so I went to some AR73's that seem to work out pretty good.

[Kern Dog]

Rick Ehrenberg from Mopar Action magazine is a huge proponent of KEEPING the vacuum advance. I agree with his belief that it is great for keeping the plugs cleaner, burning the fuel more fully and extending the oil change intervals. Tuning it is a bit tricky though.
Looking at your build, it looks similar to mine. I also run a MP distributor but I use the vacuum advance. If you pull out the reluctor and pickup, you can see the adjustment in there. Some were adjustable with allen screws.
I run Edelbrock aluminum heads with a calculated squeeze of 10.8 to 1. I am limited to 31 degrees plus vacuum advance because of the limitations of this commie state 91 Octane swill. My initial is set to 17 degrees. This equates to a total mechanical advance of 14 degrees. It actually works quite well for me. Running iron heads with high compression is difficult. I'd be surprised to see you running 30 degrees even with 93 octane without detonation. You will need better fuel or lower compression to live on the street.
My Charger got almost 13 mpg last year on a 900 mile road trip. I have a 440/493 with the dinosaur ancient tech MP '509 cam, 850 vacuum secondary carb that is OVERjetted, 2" TTI headers, a 727 with a Gear Vendors overdrive, a 3.91 diff (3.05 in overdrive) and 28 1/2" tires. There is more mpg to be had in my combo. A modern cam like yours and a well tuned ThermoQuad could get me over 15.

[69wannabe]

I pulled the distributor yesterday and done some adjusting and came out with 19 degrees mechanical advance and I am running bout 16 initial for a total of 35 degrees rite now. I pulled the heavy spring off and ran it so I could see how far it was advanceing at a lower rpm. After I got my reading I pulled it apart and put it back in there. My engine is a lower compression 493 with the diamond dish pistons and I am bout in the high 9's on compression which can usually survive on 93 octane. Im gonna try the timing there and if no pinging thats where i'm gonna leave it. I got a little play room in case it does ping I can go down a degree or two and still have some decent initial and total timing!! I ran it awhile and done some carb adjusting to compensate for the higher timing which was pretty much just idiling it down and the mixture screws were pretty much the same both ways so that didnt take but a sec. It rev's good and starts good and if it wasnt raining I would know how good it runs out but maybe by saturday I will know!!