Distributor Re-Curving 440-6

[Chris Gray]

Hi All,

I have a 440-6 six-pack that's stock with a Bob K cam in it.
I'm running a NOS MP 432 dizzy that has 13 degrees of mech advance built into it.
I need to run 38 degrees of total advance which I am, but I feel there's still more power in the engine.
I can swap out the heavy spring for a lite one to bring the timing in by 2500-3000.

What I don't understand is why folks are welding up the advance slot???
Should I leave my advance slot at 13 and just change springs or start welding and filing??

Thanks

[kawahonda]

The slot is welded to be able to run more initial. I've never heard of a "13" slot before. A 13 stamped slot would be 26 mechanical. Too much for my tastes.

A good all around setting is 15-17 initial and 34-36 total at around 3000 RPM. If you're running 38 total I assume you've got some damn good fuel on hand.

[Chryco Psycho]

The slot controls the total amount of advance possible typically more like 24*
The springs control what rpm the advance happens at .
so the 2 are totally different functions ,  I am not sure how you determined you only have 13* of advance but that would mean to get 36* total initial timing would need to be set at 23* at idle .
the springs only control how fast or slowly you get to total timing , often a lighter spring will help but if it is too light it can ping if the timing gomes in too fast or worse the timing can wander at idle & not stay steady causing idle inconsistancy .
I once had a 340 6 pack I was tuning & it would idle at 500 rpm or 1100 , & I toe the carbs down & tried to find the issue But it was not fuel related , at 500 rpm the idle was consistant & the advance had zero effect , turn up the idle slightly & the mech advance would move bringing up the idle speed , I changed the lighter spring to a slightly heavier one & the idle was controllable  anywhere between 500 & 1100 rpm .
I would suggest using a lighter spring as 13* advance is already a very short curve & see how things change .

[Chris Gray]

Thanks for your response,
I asked Google what the advance of a 432 dizzy was and someone from a previous post stated it was 13, so I'm unsure myself.
Does anyone know the advance number of a MP 3690432 dizzy?

From what I've read 13 degrees x2 = 26 mechanical??? + 12 initial =38 total??? so why fill and file slots???
Yes we have 98 pump gas where i am, 

Or am i just confusing myself???

[kawahonda]

12 initial is trash, especially with the gas you have.

Please invest in a digital timing light. Disconnect vacuum advance and plug it. Then tell us exactly what it's doing.

No one, ever, will tell you how much your dizzy is advancing by a Mopar part number.

Get a timing light, and see what maximum advance you have right now.  You may find that being at a true 38 total (without vacuum advance) is too hot. Best way to test for total is highway speeds, at load, flooring. Testing for total timing is NOT peeling out, short burst low speed accelerations.

You will also be able to figure out how much mechanical (the slots) are adding.

Ultimately, I recommend you sending your dizzy in for a recurve. PM me for some names. BUT, even better that you are able to understand 100% what your distributor is doing, what is too much at load, and what is too high initial to get starter kickback. Timing light will make you a pro...

Many dizzy pros will go off highest vacuum for your initial. I partially agree. I agree in the sense that you should explore the boundaries. For my 340, 18 initial caused no issue starting, hot. I never cared to push it further.

What I'm saying after all this, is to get a innova timing light, and jot down notes...

I pulled apart only 2 Mopar small block distributors and have found they are all stamped with "9" which equals 18.  18 is a magic ticket for many, many engines. A timing light will confirm yours...

[RUNCHARGER]

I would shoot for 16-18 degrees initial with a total of 36 degrees, all in by 2000-2500RPM. That will make it feel snappier.

[Chryco Psycho]

I would weld the inside of the slots so you get down to 18* advance set total @ 36*

[71383bee]

 

100% agreed with all 3 posts above.  You can not time the motor based on part numbers and what it should be type quotes.  Every motor is slightly different based on a variety of factors but if your in a pinch and need to get moving setting for 34-36 total and 15-17 initial will get you darned close to ideal in most situations.  And the only real way to do this is to get a dial back timing light and check and see what you are dealing with. 

On any car I've owned the first thing I've done is have someone rev the motor up while seeing where the timing stops turning and hold it.  Set total at 34.  To do this dial the advance to 34 on the gun and adjust the dizzy to where you see the timing mark hit 0.  This part can seem scary as the car is screaming at 2-3k rpm with your head under the hood and you have to reach in with a box wrench and lightly loosen the distributor and rotate it with your hand all while keeping the light on and watching the mark.  I admit...it can be a bit nerve wracking.  After it is set have your partner let off the gas and let it settle to idle and dial the advance dial back down on the gun to see where the timing mark creeps back to 0.  At 0 read the number on the gun...that is initial.  On stock distributors I have seen typically 24 or more advance is pretty common which for our cars is a lot.  As stated earlier you will find that initial is king.  This step alone usually results in a much happier motor as the initial is often quite a bit higher than wherever it was before.  After that to dial it in right as suggested you will need to get into the distributor itself to modify the advance curve.  However, again if your in a pinch and are unable to crack open and adjust the distributor, this step alone is often a decent improvement over whatever was there before.  Sometimes it was good enough I'd readjust the carb idle speed and mixture for best vacuum, pull out the equipment, shut the hood and move on with life.  This is all done mind you with the vacuum advance disconnected and carb port plugged btw.       

I'm willing to bet that 3 out of every 4 "its not running right" posts revolve around not getting this very basic but completely necessary step done right.  Setting timing can be a little intimidating, but its absolutely critical and with the help available from the guys on here along with a dial back timing light, a vacuum Gauge, a flat headed screw driver, and 1/2" box wrench can lead to a HELL of a difference in turning your car into  .   

[Chryco Psycho]

I bet there is more than 25 % of the car running properly on this site as I have been telling people to ditch the timing light & tune the engine by ear for over 20 years now  . But yes bring up the RPM & advance the timing until the engine runs its best !

[71383bee]

Good point!  My point meaning a lot of things are resolved with this very  basic step. 

I've got friends that will have no issue tearing a car apart and putting it together but they treat timing as though it's voodoo! 

To get a decent tune you gotta get the timing right.


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[Kowal]

A couple of things...

- get a full advance timing light if you haven't yet.   One that has a digital read out as you work the timing.

- You don't need to weld the distributor slots if you add a FBO advance limiting plate.    Just drops in after partially disassembling the top of the distributor.   You can dial in with the plate how much advance is in the distributor.

- doing all of the above...I typically set up my cars for 16 - 18 degrees at initial (with vacuum line temporarily plugged) and 32'ish full advance.   A little lower than what is recommended here, but I am driving on the street in traffic and it seems to work well.    I turn the vacuum can adjustment CCW a couple of turns to delay when the vacuum kicks in, but I do use the vacuum.,   It does help driveability.

- I go a little further than most in that I have a Sun Distributor machine.   The springs that come with a stock Mopar unit these days are maybe a little quick on bringing a lot of timing in, but if you weld the slots or use the FBO plate it won't matter too much.   If it does you will know it at part throttle around 35 to 45 mph where you might hear some detonation if it was too much...but other adjustments can help that as well.

FBO is 4secondsflat.com.