Timing/Advance Problems after MSD 6al install - 440

[mindless1]

(generally stock 69 440 Charger RT)

I thought I'd run this past the gauntlet of knowledge before i start replacing parts...

As part of troubleshooting another weird problem where my car wont rev past 2000 rpms I just wired in a borrowed MSD 6al ignition box in place of my mopar orange box.    (the original post for the problem is ( http://www.dodgecharger.com/forum/index.php/topic,34640.0.html )
After installing the MSD box I retimed it to around 7` BTDC at idle.    However I found that if I tried to give the motor any RPM's whatsoever, it immediately began to detonate.  Checking it with the timing light I found that the second I revved off idle, the timing advanced off the charts (thus the detonation I presume).    However, I found that this problem went away if I pulled the vacuum tube off of the mopar distributor. 
My question is - is this likely a problem with the entire distributor, the vacuum module, or something with the ignition elsewhere? 
If this is related to the springs in the distributor and the tensioning of them - why would this problem only have appeared due to the new MSD box?
And - is it likely that whatever is causing THIS weird issue also the cause of the problems I was first trying to solve? (not revving over 2000rpm)

*Though I've heard the pro's and con's of vacuum advance I'm fairly certain I want to keep it in place for some economy when cruising.

Thanks for any thoughts!

[firefighter3931]

Where have you got the vac advance plumbed into the carb ? Ported or manifold vacuum ? Are you using a dialback light....if so some of those won't work properly with a multispark ignition. 

It sounds like your distributor is pulling to much advance into the engine causing detonation. You might also have to modify the advance mechanism to limit mechanical advance. On most BB builds i start with at least 14* of base timing and limit the total to 36-38 all in by 2800.

Try mapping out your advance curve in 200rpm increments and post the results. I'd like to see how much total advance you have, how fast it's coming in and where it stops.



Ron

[mindless1]

Thanks Ron!  That makes sense.   I'm going to try to get that done tomorrow and this weekend, as soon as I'm done researching what dialback light is!

[firefighter3931]

A dial back timing light has a dial on it to "zero-in" the timing. If your timing light does not have the dial back feature it should be reading correct. I know for a fact that the high dollar Snap-On dialback timing lights don't work at all with Multi-Spark boxes like the MSD 6al.

Another thing that can occur and often does.... is slippage in the outer ring of the harmonic balancer. This happens mostly with stock balancers that are old and the rubber that bonds the hub to the outer ring vulcanizes. This in turn will cause the outer ring to shift and give you false timing results.



Ron

[flyinlow]

Set up your mechanical advance for max power without spark knock. Suggest total of 34-38 deg. by 2500rpm. experiment

Then try adding ported vacuum advance. Ported will only supply vacuum above idle when there is  medium to high vacuum in the intake manifold.

This is done to increase part throttle/cruise fuel economy. Will not increase HP.

I have to limit my vacuum advance to about 10 deg. or it will knock on 92 octane. (446  10.6 cr Eddy heads)

[aifilaw]

I would bet that your vacuum advance was plugged into your main manifold vacuum instead of your backup vacuum idle circuit port.

[mindless1]

For reference the timing light is a craftsman - it has no dials for adjusting dial back. 

As for the possibility of a slipping balancer - while I rule nothing out with this fickle car anymore - I think that one isn't too likely since the motor seems to respond as if the timing trully is that far off.  How in the heck am I going to even measure 34 degrees of advance on the timing pointer, do I need to extend what is there?  I readily admit that I have little experience with timing. (if its not brutally obvious).  Thanks for the ideas. 

http://cgi.ebay.com/ebaymotors/_Automotive-Tools__Craftsman-1-2302-Inductive-Timing-Light-No-Box_W0QQitemZ180303387088QQadiZ2871QQadnZAutomotiveQ20ToolsQQcmdZViewItemQQptZMotors_Automotive_Tools?_trksid=p4506.m20.l1116

[flyinlow]

Measure the distance between the zero mark and the 10 deg. mark . Multiply by 3 and by 4. measure from zero and paint a 30deg and a 40 deg advance mark on your balancer. Now you can set you advance with a basic timing light.

Or by a timing tape and stick it on the damper. Or a new damper with marks.

[flyinlow]

If you have a 7.25 inch damper.

7.25  times  3.14   divided by 36  =  .632 inch per ten deg.  or about 5/8 inch per 10 deg.

30deg = 1.90 inchs  from  zero
40deg = 2.53 inchs from zero

[70daytonaclone]

Dam flyinlow your scaring me!LOL

[flyinlow]

Measure with a micrometer, mark with caulk, spit it with an ax. 

[firefighter3931]

For reference the timing light is a craftsman - it has no dials for adjusting dial back. 

As for the possibility of a slipping balancer - while I rule nothing out with this fickle car anymore - I think that one isn't too likely since the motor seems to respond as if the timing trully is that far off.  How in the heck am I going to even measure 34 degrees of advance on the timing pointer, do I need to extend what is there?  I readily admit that I have little experience with timing. (if its not brutally obvious).  Thanks for the ideas. 

http://cgi.ebay.com/ebaymotors/_Automotive-Tools__Craftsman-1-2302-Inductive-Timing-Light-No-Box_W0QQitemZ180303387088QQadiZ2871QQadnZAutomotiveQ20ToolsQQcmdZViewItemQQptZMotors_Automotive_Tools?_trksid=p4506.m20.l1116

I have the same timing light and it works fine with MSD multispark ignition....no worries. 

You can mark the balancer with a sharpie using the measurements Flyinglow provided above or purchase some timing tape from MP. If you use the timing tape make sure to clean the balancer with brakeclean. I've also used clear nail polish over top of the tape to protect it and keep it in place.



Ron

[mindless1]

Minor update that may or may not further indicate my problem!  I just went to confirm where the vacuum advance was hooked to - and it is connected to the "3/16 timed vacuum" on the passenger side of the carb.  According to the spec sheet at http://edelbrock.com/automotive_new/misc/tech_center/install/1000/1406.pdf that means it is hooked to the "timed vacuum" versus the "manifold vacuum".  I'm not sure if this would make THAT much of a difference and will try changing it once I get the timing marks extended per the other suggestions.    (and for the record, I'm painfully aware of how under spec this carb is for the motor, I didn't have any choice at the time it was built and a new carb/manifold is on the shopping list!)

[mindless1]

Another update....some further reading makes me believe the vacuum connection to the carb is in fact correct (at least better than the manifold vacuum option). 
I just downloaded the distributor instructions from MOPAR as well as some other good reading on timing - I'm going to finally learn this process then give it a go.  Here's an article recommended to me - if anyone has any others those would be welcomed as well.
http://www.chevyhiperformance.com/howto/97438/index.html

Does anyone know if it is possible to purchase a replacement vacuum advance module for a MOPAR distributor?  I can find them for mallory, but not for MOPAR.  I'm assuming they are not universal?  Should that be the problem would I have to replace the whole distributor because of a few dollar part?

[flyinlow]

NAPA has them . About $25. They made ones that where adjustable with shims for the amount of vacuum it took to advance them . If those are still avialable.

Craig