My timing curve

[BananaDan]

Here you go Ron.

24* Idle 1100rpm
26* 1300
28* 1500
33* 1700
33* 1900
33* 2100
33* 2300
33* 2500
33* 2700

[firefighter3931]

Ok, that might explain the detonation issues 

The total timing is coming in a bit early (1700rpm) so the next thing I would try is a heavier spring in the distributor to slow down the curve. Shoot for total timing all-in at 2600-2800 rpm and see how that works. You can also dial in an extra 3* of mechanical advance to five it 36* total....that won't cause any issues and it will pick up some power. 


Ron

[BananaDan]

How do I know what strength spring is in there now, and which to go to?  Are they color coded?

[firefighter3931]

How do I know what strength spring is in there now, and which to go to?  Are they color coded?

It's been awhile since I was inside an MP distributor so not sure on the color thing but I do remember something along those lines. Basicly you need a heavier spring (than what's in there now) to slow down the advance curve. Often it's trial and error but Mike might have a spring set that he's used on customer cars. Mr Gasket makes a kit that the Chrysler guys use but can't remember the part number off hand. 



Ron

[BananaDan]

Thanks.  I'll have her at Mike's in a month or so for the MSD install.   

[terrible one]

Dan,

I just finished tuning my MP distributor. After some reading I found that it is basically the same as a Mallory Unilite and uses the Mallory YH advance system. I ordered the Mallory spring kit, #29014 and although it's a little pricey it does include the degree sticks to set the total advance with and graphs/ charts of the advance curve for all of the spring combinations.

Ron's right, the distributor will have Mallory's purple spring (although mine was unpainted it had the same physical dimensions as the purple spring included in the kit) and their brown spring if it's the same as mine was.

The "purple" spring has slack in it so that it lets the plate advance basically instantaneously (no resistance) the first few degrees then the spring has tension on it and provides resistance.

I started by removing the purple spring and messing with some of the combos that utilize 2 "normal" springs, but I ended up using one purple spring and one orange because my 383 was sluggish at lower RPMs, it wants lots of advance fast but too much initial and the starter was getting beat up so the 2 stage curve worked best.

Brown/ Purple (stock) 22* initial w/ 22* of mechanical advance
800  -22*
1000-24*
1200-28*
1500-34*
2000-38*
2500-40*
3000-43*
3500-44*


Brown/ Orange, 24* initial w/ 18* mechanical advance
800 -24*
1000-24*
1200-24*
1500-26*
2000-30*
2500-36*
3000-36*
3500-36*


Pink/ Orange, 18* initial w/ 18* mechanical advance
800 -18*
1000-18*
1200-19*
1500-22*
2000-28*
2500-34*
3000-36*
3500-36*

Purple/ Pink, 20* initial w/ 18* mechanical advance
800 -20*
1000-22*
1200-31*
1500-34*
2000-36*
2500-37*
3000-38*
3500-38*


Purple/ Orange, 20* initial w/ 18* mechanical advance
800 -20*
1000-20*
1200-26*
1500-31*
2000-33*
2500-35*
3000-38*
3500-38*


I would have left it at the Purple/ Pink combo but even after bending the perch a bit to increase spring tension to hold off the advance I still had a little bit of RPM creep going from drive to park. I hope that helps!  


**EDIT: Sorry, by the time I finished writing this and waiting for the computer to unfreeze I see now your post that you are going to MSD, ah well maybe someone can use it

[BananaDan]

Thanks!!!