Custom distributor curving.
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pntastar69
Well-Known Member
Please do!!!
thanson_mopar
Well-Known Member
please post pictures and show us how! did you recurve a stock SB distributor?
thanson_mopar
Well-Known Member
sorry for the ignorant question but could the same concept be applied to a electronic ignition distributor?
dusterny
Well-Known Member
Yes what thanson said. Mine is out of a truck.
Ok guys sorry this is late but I was trying to document some spring rates
on the advance. The Mr. Gasket curve weights had all my advance in by
1000 rpm, not exactly what they advertised.
Again this is for a small block points distributor.
First off, pull your disty and get a clean workbench. Take off the cap and
rotor and the first picture is what you see. Next remove the 4 screws on
the outside. Two hold the vac advance and the other two hold the guts
to the housing. You can twist the insides out a little to free the vac
advance pin so it will drop out the bottom of the rotating plates and
slide her out of the disty.
on the advance. The Mr. Gasket curve weights had all my advance in by
1000 rpm, not exactly what they advertised.
Again this is for a small block points distributor.
First off, pull your disty and get a clean workbench. Take off the cap and
rotor and the first picture is what you see. Next remove the 4 screws on
the outside. Two hold the vac advance and the other two hold the guts
to the housing. You can twist the insides out a little to free the vac
advance pin so it will drop out the bottom of the rotating plates and
slide her out of the disty.
Next you will see the mechanical advance limiters, weights, and springs.
There is a small retaining ring in the center of the round housing that holds
the T bar that fits over the weights and springs. I found the easiest way
to remove it is with needle nose pliers and grab one side and twist it out.
After you remove it, the T bar will with a little force slide off. Now you can
see the weights and springs. Notice the springs are different. They control
at what RPM your mechanical advance starts to come in and when it is all
in. The pins on the weights that fit into the T bar control how much advance
you get. The T bar I have is stamped 15L which means you will get
15x2 or 30 degrees of mechanical advance. If you are running more initial
you need to limit your total mechanical advance. For my application I want
to run 18-20 initial. That leaves me only 14-16 left in the distributor
mechanical advance to give me 34 total.
There is a small retaining ring in the center of the round housing that holds
the T bar that fits over the weights and springs. I found the easiest way
to remove it is with needle nose pliers and grab one side and twist it out.
After you remove it, the T bar will with a little force slide off. Now you can
see the weights and springs. Notice the springs are different. They control
at what RPM your mechanical advance starts to come in and when it is all
in. The pins on the weights that fit into the T bar control how much advance
you get. The T bar I have is stamped 15L which means you will get
15x2 or 30 degrees of mechanical advance. If you are running more initial
you need to limit your total mechanical advance. For my application I want
to run 18-20 initial. That leaves me only 14-16 left in the distributor
mechanical advance to give me 34 total.
To limit the total advance you need to shorten the travel of the slots on
the T bar. Remember distributor advance is x2 to the total. So if I am
setting my initial at 18 and I want 34 total that leaves me 8 degrees
advance in the distributor, 8x2=16 +18=34.
You will need to weld or solder the outside of the slots to shorten the
travel to limit your total. The numbers I have are close and should get you
within 2-4 degrees. I have found I am about 2 degrees off but it might
vary from distributor to distributor. Use the numbers below for reference.
dist. degrees / slot size
6.............. .340
7............... .355
8............... .375
9............... .390
10.............. .405
11.5 ........... .420
12.............. .435
13.............. .445
14.............. .460
15.............. .475
16.............. .490
17.............. .505
18.............. .520
This photo shows the shortened slots.
Make sure all the sharp edges are removed and the slots are clean to the
weight pins can move freely in the slots.
The tricky part for the curve is getting the springs to come in when you
want. If you are happy with your current curve, put it all back together
and away you go. If you want a performance curve to bring in your total
around 2200-2500 rpm you will have to play with springs to get that set
right. Many have had luck with just removing the heavy spring. For me
that just brought my total in by 1500 rpm which is too low. I have two
of the lighter stock springs in and will fire that up tomorrow and let you
know how that works.
the T bar. Remember distributor advance is x2 to the total. So if I am
setting my initial at 18 and I want 34 total that leaves me 8 degrees
advance in the distributor, 8x2=16 +18=34.
You will need to weld or solder the outside of the slots to shorten the
travel to limit your total. The numbers I have are close and should get you
within 2-4 degrees. I have found I am about 2 degrees off but it might
vary from distributor to distributor. Use the numbers below for reference.
dist. degrees / slot size
6.............. .340
7............... .355
8............... .375
9............... .390
10.............. .405
11.5 ........... .420
12.............. .435
13.............. .445
14.............. .460
15.............. .475
16.............. .490
17.............. .505
18.............. .520
This photo shows the shortened slots.
Make sure all the sharp edges are removed and the slots are clean to the
weight pins can move freely in the slots.
The tricky part for the curve is getting the springs to come in when you
want. If you are happy with your current curve, put it all back together
and away you go. If you want a performance curve to bring in your total
around 2200-2500 rpm you will have to play with springs to get that set
right. Many have had luck with just removing the heavy spring. For me
that just brought my total in by 1500 rpm which is too low. I have two
of the lighter stock springs in and will fire that up tomorrow and let you
know how that works.
Reverse your teardown to put it all back together. Make sure that the T
bar moves freely and there is no binding in the slots at all.
Dont forget the snap ring in the center holding the T bar to the disty
shaft. I put some light lube on all rotating parts and called it good to go.
Hope this helps out.
bar moves freely and there is no binding in the slots at all.
Dont forget the snap ring in the center holding the T bar to the disty
shaft. I put some light lube on all rotating parts and called it good to go.
Hope this helps out.
Yes, absolutely. It can be done to any Mopar distributor. I don't have
pictures to share on any others though. I bought a rebuilt unit for 37 dollars
and redid it while the bone stock one was still in the car. It is not that
hard to do to only limit the total advance, adjusting the spring rate
is a little more trial and error unless you have a distributor machine.
abodyjoe
Well-Known Member
Nice work. That's the chart from mopar enthusiast magazine. Ted Wagner wrote a couple very good articles on how to do that. Think it was in the first two issues.
The two light springs will bring total in between 1000 and 1200 rpm. My personal experience is that on the street they seen to run better with total coming in at about 2200 rpm Wich you get by using the stock light spring and one real light spring like you used. Curving your dist is one of those real easy things that for some reason people are scared to death to try. A properly curved dist makes a huge difference.
The two light springs will bring total in between 1000 and 1200 rpm. My personal experience is that on the street they seen to run better with total coming in at about 2200 rpm Wich you get by using the stock light spring and one real light spring like you used. Curving your dist is one of those real easy things that for some reason people are scared to death to try. A properly curved dist makes a huge difference.
Yes that is the chart from Mopar Enthusiast. I did find that a slot length
of .375 gave me one degree less than posted though or two on the crank.
I had the one light spring and one from a Mr. Gasket spring kit and all
my advance was in at 1500 rpm. Tonight I will try it with the two
stock light springs and hopefully that will put me about 2200-2500. If
not I will have to play with the heavier spring. It's important to keep in
mind that shortening the slots also changes the spring rates too so that
the .100" I shortened the slots might put the stock spring rate about right
on for me. I'll keep you posted.
I hope all this info saves others time, and don't be afraid to dig into it.
It's probably the cheapest performance booster you can do!
I am far from an expert so if anyone sees error with my posting please let me know.
Longgone
John/68 Barracuda & Dart
Great thread, I like play by play "how to" articles like this.
I looked in the tech archives first and didn't see anything.
It started out as me taking a bunch of pictures so I wouldn't
forget anything or how it all went back together!
It is a lot easier than I had originally thought to limit the total advance.
I am still playing with spring rates to get it good for my engine. It makes
a huge difference for even the temps my car will idle at. Going from
12 initial to 18 has dropped me 10-15 degrees and I also have very
much improved throttle response. I'd say it was well worth the effort.
Burntorange70
Well-Known Member
Good info.
abodyjoe
Well-Known Member
Yea he wrote that the sizes were ball park and you would have to mess around with it to get perfect. I think you can read the magazine for free for those who haven't seen it. Go in the archives and look in the first two issues. Tells ya about the slots and how to adjust the vac advance
abodyjoe
Well-Known Member
What's your combo? If the dist. Has never been touched then you can probably benifet from curving the dist. Even on a stock motor
Well, like I mentioned above, I'm not an expert on this but here's how I
figured it.
I set my initial timing where the cam liked it by setting for max vacuum
at idle. As you advance you timing your idle will speed up so you will need
to keep bringing your idle speed down so it stays at a consistent rpm. You
might be surprised how much advance that actually is. When you are at
max vacuum, back off one degree of advance. If your at more than 20 before you might get starter kickback and have to adjust for that also.
Once you have your initial set, you will need to limit your total to around
34-35 for a small block non-stroker. I think strokers need a little less total.
That's how I set mine up. I have 18-20 initial and limited the mechanical
advance in the distributor to give me a total all in of 34 advance.
I see, thanks :thumbup:
abodyjoe
Well-Known Member
yup pretty straight forward. and the different dist. have differen tavance plates too. maybe you'll get lucky and have one perfect for set up.
AdamR
Big Member
I had idle issues after installing 2 lights springs. The distributor was trying to advance at idle causing the idle to dance around.
I agree with Joe, Its probably best to use only 1 light spring.
I agree with Joe, Its probably best to use only 1 light spring.
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