school me on dist

[1930]

Thanks for the information guys, the trucks engine is partially disassembled at this point. I will be putting it back together when I am ready.

At this point I am taking the time to understand things better.

I appreciate all the input.

 

[805moparkid]

dont try to make it harder than it is

Governor controls mechanical advance (number stamped x2 or what ever you modify it to)

Springs make the curve come on sooner or later, or if you have way different springs you'll get two steps in timing increases

Vacuum pod reacts to vacuum to ad more timing under high vacuum situations. The number stamped on the arm x2 is total movement, when the pod comes in and starts its "curve" is controlled by the allen inside the pod if adjustable.

 

[1930]

I'll try to consolidate the outstanding questions, without adding to the confusion.

I don't think people know which part your refer to as "governor". The "9R" numbers sound like what is usually stamped on the vacuum pod arm, but you say "no marks" on yours.

The vacuum advance and mechanical advance add together, so isn't an either/or situation. The vacuum advance gives more spark advance at low vacuum (near idle), up to ~15 crank degrees. When you open the throttle vacuum drops and the vacuum advance contribution disappears. This helps avoid pinging.

I never played with tuning the weights. People change springs, weights, file the slots, weld stops in the slots, etc. You could spend a lifetime fooling with that, especially on a factory distributor where getting at the weights is a bi** and removing the distributor on a slant is a messy bi**, especially if the spark plug "drool tubes" leak. I would rather type a number in the computer and be done with it, which is my longer-term goal.

Hello Bill, yes kid was right, this is what I have read is called the governor, the weights of the dist come into contact with the slots of this deal and depending on the length of the slots are allowed to sling further outward causing a more positive affect on the amount of advance.

The 13 is on the left ( longer slot ) and the 9 on the right

Can someone here explain to me why the long slots are frowned upon, it was done evidently to help with emissions, somehow advancing the dist ignition helped clean the air and possibly save fuel, but how did it do it and why wouldnt we be all looking for the longest slot we could find. ( for those of us looking for fuel economy )

 

[805moparkid]

if you ran the 9R with 30 total you could have 12* at idle which is pretty close, then your down to springs

To answer your question its what ever more did to make them pass smog.

your correct that you double the number, so a 9R is 18*, if you run 12* initial timing and a 9R (18*) you'll have 30 total mechanical timing. The reason the slot/number is so high is because they pulled the timing way back in the 70's, sometimes even retarded the timing so they still needed a good total timing number

^^^

 

[ntsqd]

The reason is that the total of the mechanical advance + the initial advance desired by the engine didn't change. The total is dependent on a bunch of fairly fixed to the engine's architectural factors (you aren't going to radically alter them with the comp ratio, size of the cam, size of the carb, etc.). So to use the longer slot (greater mechanical advance) the initial advance has to be reduced, which isn't good for anything (as I understand it) except reducing emissions at idle.

 

[1930]

Thanks Guys.......................This info was given to me by WJAJR ( I dont know his name ) on the slant forum. I hope it helps someone understand all of this better as it has for me and I am sure these contributing posts will help more people later on down the road. .............

There is a point of no return if timing advances too high generally 50 or so degrees for a light car, and perhaps 40 to 45 degrees for a brick, er, rather truck.

The engine works less to push a car through the air at cruse, and can stand timing into the low fifties with out ping or detention. A truck because it is less aerodynamic and heaver its engine can't use as much extra timing because the engine is under more of a load compared to a car.

There are three sources of timing, base, mechanical, and vacuum advance. Generally a light car's base is near 12 degrees, mechanical for a car should not go much past 30 degrees (12 + 18), and vacuum advance brings it to 48 to 52. 12+18+20


Quote: why I would want a 9R governor versus a 13


The 9R gives 18 degrees advance, and 13 gives 26 degrees.

Some slants came from the factory with base timing set between zero to 5 due to early pollution control protocol before any of the manufactures figured out how to clean up the exhaust pipe; in other words pre computers, cats, and fuel injection. These detuned low compression cars ran like crap for the years 1973 to 75, and needed a lot of mechanical advance to hit the sweet spot 28 to 30 degrees when under way.


Perhaps not the best explanation floating around out there, but I guess it all depends what one is running, and in what.


So you need to figure out what runs best in your set-up if it is non stock in any way. Tweaking of a stock set-up is also on the table, as chances are one can get it to run a bit better with better economy.

 

[1930]

And this by DusterIdiot. Again I appreciate everyones efforts to help me ( a not so bright guy ) get a handle on all of this.

You can install the longer slot, but if you set it to have more initial you could cause the engine to ping/ or detonate at a certain point because it lit the mix in the cylinder too soon. On a low compression engine, like ours giving the combustion process a "leg up" by limiting the governor and setting the base timing starts the process sooner so the cylinder builds pressure sooner...

As noted we are lucky to have a particular formula to work with on timing
(base+mechanical=30, and with vacc. advance at cruise =50...for a truck I advise to limit to 30 and 47 due to the power to weight ratio and lack of aerodynamics).

So if you follow to articles...the truck distributor would be set at:
4 BTDC base+ 26 springs and governor at just above highway cruise rpm=30 then your vacuum advance on top of it....

The super six distributor gets to light to fire off earlier:
12 BTDC + 18 BTDC springs and governor=30 then add the vacc advance.

That extra 8 degrees helps for a more complete burn of the mix compared to the 4 on the truck.

There are only a certain set of governors mopar tended to work with, and an end user like your self can break out a welder and file/grinder and make whatever version you want:

slant six 9 (super six),10( mopar performance distributor),11 (stock 1976 applications,13 (truck distributors),15 (1973-1975 cars) and points 11.5 (early to mid-60's distributors),13(late 60s to 1972 distributors)
V-8 17,18 (too much for a slant six but worked fine for those 4"+ bores)
Points could be had in anything from 9-18 (but you can't use an 8 point governor in a 6 cylinder car)

Remember emissions timing is to provide a controllable amount of pollution per the regulations and specs when everything is working correctly. This does not necessarily help with power and economy, adding a little more base timing will help get a few more HP out of a
low compression engine but may create a little more NOx (thus the need for a little more EGR in the 1976+ vehicles along with the catalytic convertor...so the combination evens the gains and losses out).

Typically when someone wants a shorter slot that 9, it desired because of the limit in timing with boosted engines, or because the performance build needs less timing due to the fuel or combination being run to stay out of detonation.

 

[1930]

Was it me I'd look for "grandad's car", the obviously well maintained car in the junk yard, and buy it's OE module. That has been what has worked the best for me with the Dura-Spark's. Never had a JY sourced module fail, only those bought new.

I have been looking for some time now, since purchase of the truck many months ago and even more diligently since you first suggested it a few posts prior to this.

Here in Florida I have yet to see a module that has not spewed out the sticky stuff from the backside of it....the heat does them in.

 

[1930]

Get a 1973 dart slant six dist. I like the Cardone remand ones from O'Reilly.
Matching ballast resistor.
Mopar Performance harness.
As far as ECU...Napa usually sells quality parts,or look for a good name brand one off eBay.

I have spent some time with this, buying and then returning dist because they were long slot governors, 13 and 15s plus. It is true evidently that they are not building these dist. to year of specs but instead putting in the part that is within the shortest reach.

Using one of these I now understand will not give me the opportunity to have any room for any decent amount of initial/base timing.