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Distributor spring recommendations
https://slantsix.org/forum/viewtopic.php?t=30579		 Page 1 of 3
Author:  Reed [ Sat Aug 16, 2008 2:44 pm ]
Post subject:  Distributor spring recommendations
I am starting over with recurving the distributor in my brother's van.

Specs:

1983 Dodge shorty van (roughly 3,000 pounds)
225, rebuilt to 76 specs with stock 76 cam
727 tranny
3.2 rear gears

I have a VC-208 vacuum pod on order, but it hasn't arrived yet.

My current vacuum pod comes on at 9-10 inches and is all in by 14 inches. The arm on the pod is stamped 9.5.

I have a R9 governor.

The following is a picture of all the various springs I have to play with, grouped by weight:

Image

The two springs on the bottom were the ones I had in the van that seems okay, but I had a rather flat power band until the transmission kickdown came in.

The slant likes 32 degrees total mech+initial adviance (right?), so with the 9R governor I set initial timing to 12 BTDC. Vacuum advance doesn't come in until 10 inches of vacuum, and the van cruises at about 10 inches of vacuum. Whenever I try to accelerate quickly, vacuum drops to about 5 inches of vacuum, so with this vacuum pod I don't get any vacuum assist unless I use VERY light throttle or I am spinning pretty fast.

SO: What do folks recommend as a starting point for tuning the distributor curve? Right now I am thinking about replacing the heavy spring that I was using with a lighter one.

I realize that this will just be ballpark and I will need to fine tune both the vacuum advance and the springs as i drive, ubt how about just a general idea for starters?

Thanks!
Author:  DusterIdiot [ Sat Aug 16, 2008 5:36 pm ]
Post subject:  Allen wrench...
So have you taken an allen key and stuck it down the snout of the vacc pod to see if you can get the vacc. engagement point to move up a bit?

VC-208 is going to be heavy handed for a 'brick' powered by a brick... you'll probably have to go back to the stock springs to use it... (less mech advance heavy reliance on you Vacc. Pod being in all the time... and a little less initial)...

If the van were more like a car you'd have a couple of better options in the picture... given your parts and vehicle, I might be more privy to use the VC-185... high load, large vacc. drop on throttle response, the slant will want a bit less total timing (30 init+ mech is fine... 45-47 with vacc. advance might be more realistic..)

-D.Idiot
Author:  Eric W [ Sat Aug 16, 2008 10:28 pm ]
Post subject: 
Hey Reed. Since the van is heavy like my Satellite, I would use the heavy light spring (looks like the right spring in the middle row) and the shorter of the stiff spring middle spring in top row). I loose some response on acceleration, but at freeway speeds the engine pulls well from 60 up to 80 or so, then starts to flatten out. I also tuned the vacuum pod to come on at about 20 inches or so of vacuum. Initial advance set to 8 BTDC. Works for me anyway.
Author:  Reed [ Sat Aug 16, 2008 10:45 pm ]
Post subject: 
Hey, thanks Eric! I appreciate the recommendations.

The vacuum can is adjustable but the adjustment makes the vacuum advance come in at 10 or higher. The can starts at ten with the adjuster screwed all the way clockwise (in). I just went out and adjusted it so the advance starts at 13 and is all in by about 20.

I think I am misunderstanding the way the vacuum advance owrks. If I want to get a heavy load like this van moving from a dead stop, I want to rely more on mechanical advance than vacuum? Accelerating will be a high load low vacuum event that will not trigger the vacuum advance. So i want to tune it so the vacuum advance only kicks in during situations of 13 inches of vacuum or higher? :?: :? :?:

I am tuning for max MPG balanced with max torque. Theoretically this van will be used to haul five people + band gear so the motor will be working to get the van above 55. It rarely sees the high side of 3000 RPM too.

I need to button this back up and drive around for a bit and see how it does. However, I am about to leave on a week long vacation so I will have to return to this project in about a week.

I truly appreciate any suggestions and tips. Thanks!
Author:  Reed [ Sun Aug 17, 2008 12:39 pm ]
Post subject: 
Well, looks like the vacation is off, my sister got a migraine headache. :cry:

So I put the distributor back together and took it for a spin. I also changed the vacuum source for my vacuum guage form the #6 intake runner to a T fitting in the choke line.

I switch springs to the ones Eric recommended in his post and bumped the based timing back down to 10 degrees BTDC. Of course, when i pulled by dial-back timing light ff the shelf I discovered taht it has died and doesn't read consistently so i can't measure the mechanical advance sitting still.. :roll:

I drove the van around town and took it out on the highway.

Throttle response is still pretty slow, but once up to speed the van feels like it has a bit more power. I actually got the van up to 70 MPH on a long straightaway with it floored. But it still feels like something just isn't right somewhere.

The van gets 21 inches of vacuum at idle, but light acceleration drops the vacuum down to about 10-12 inches. Average acceleration puts me down to 5-7 inches, and I spend much time at 0 inches. The vacuum advance pod is adjusted to come on at 13 inches and is all in by about 19 inches.

I cruise at 55 at about 2500 RPM with 7-10 inches of vacuum. With this setup, it looks like the vacuum advance hardly ever turns on and I am running almost entirely on mechanical advance.

The loop on the heavy spring I am running (the red one in the middle of the top row) is so big that as soon as the distributor starts turning the wight advances almost to the end of the R9 governor slot. If I had to guess, it feels like I am not getting any vacuum advance and almost all of the mechanical advance is "in" by 2000 RPM.

Some of the lack of power I know is due to the fact I am running a 2280 instead of a BBD, but this feels like more than that.

Should I get a different governor? A different advance pod?
Author:  emsvitil [ Sun Aug 17, 2008 1:54 pm ]
Post subject: 
With a cruise at 7-10", I'd put in a 4.5-5.5" Power valve and get a vacuum pod that starts at about 5" (can be raised)
Author:  Reed [ Sun Aug 17, 2008 2:07 pm ]
Post subject: 
Well, I have a VC-208 vacuum pod on order (supposed to come in at 5) but I don't know of any power valve replacements for the Holley 2280.
Author:  emsvitil [ Sun Aug 17, 2008 2:51 pm ]
Post subject: 
According to this: (half-way down)

http://www.autozone.com/az/cds/en_us/09 ... oPages.htm


the power valve is mechanical and adjustable.

So I would assume you're not in the power valve unless you're at WOT
Author:  Reed [ Sun Aug 17, 2008 3:06 pm ]
Post subject: 
COOL! Thanks! I didn't know about that adjustment! I will give it a try.
Author:  65Dodge100 [ Sun Aug 17, 2008 3:42 pm ]
Post subject: 
Reed,

I’m watching this closely because I have a truck that I’ll have to do this to. I’m hoping that you figure it all out for me before I get to it!

Quote:
when i pulled by dial-back timing light ff the shelf I discovered taht it has died and doesn't read consistently so i can't measure the mechanical advance sitting still..
SlantSixDan has a good alternative to a dial back timing light (or timing tape).
Quote:
The loop on the heavy spring I am running (the red one in the middle of the top row) is so big that as soon as the distributor starts turning the wight advances almost to the end of the R9 governor slot.
It sounds like your light spring may be too light or has too much play in it? It shouldn’t have a long loop like the heavy spring and should be in tension constantly.

HERE and HERE are a couple of descriptions just in case.

Danny
Author:  emsvitil [ Sun Aug 17, 2008 3:47 pm ]
Post subject:  timing light
Once upon a time I dropped my timing light and it quit working.

I took it apart and found some loose connections.

Reseated everything and it was fine.

:wink:
Author:  DusterIdiot [ Sun Aug 17, 2008 4:23 pm ]
Post subject:  Jeez...
Quote:
The loop on the heavy spring I am running (the red one in the middle of the top row) is so big that as soon as the distributor starts turning the wight advances almost to the end of the R9 governor slot. If I had to guess, it feels like I am not getting any vacuum advance and almost all of the mechanical advance is "in" by 2000 RPM.
That's why I told you to use the stock shorty spring, the 'heavy' spring's job is the limit the travel of the weights and slow it down before it bounces off the end of the governor slot... Mopar did a pretty nice job of matching heavy springs to the slots (you want ot have fun? Throw a 1976 heavy spring into a 1974 long slot distributor... it's fun to see it limits out at about 8-9 dist degrees, but at about 6-7000 rpm you get another 1-2 more degrees out of it... like that helps...LOL)... the light spring allows the advance to ramp up to a certain point until the slot or the heavy spring limits this... if you have a heavy vehicle you will need a moderate spring so it won't just 'ramp up', like the 'drag race' distributor you have now...
One nice secret about recurving is to install the heavy spring... put the governor back on without the 'c' clip and see how the weight pin moves with limit or relation to the loop, then next you want to check the light springs and see how much tension it takes to get it to wind out... you can also use an 11/32" wrench to pull some of the loop's orientation in a bit, but you have to knock the pin out of the dizzy gear, and pull the whole shaft...


Hope you get you timing light fixed, it sounds like you are over advanced down low, and once the load and mix are 'right' in the upper rpm band, then the 'power' starts coming on...

-D.Idiot
Author:  Reed [ Sun Aug 17, 2008 5:37 pm ]
Post subject: 
Great suggestions guys! I gues I thought I knew more about tuning distirbutors than I really do.

My sister took some killer headache meds so the vacation is back on :D but I will be digging into this when I get back.

From what I am reading, it sounds like I DON'T want a spring that has the loop on the end because that contributes to over advancement down low, right? Sounds like I want to run some medium weight springs with no loops? :?:
Author:  DusterIdiot [ Sun Aug 17, 2008 6:59 pm ]
Post subject:  Yes and no...
Quote:
From what I am reading, it sounds like I DON'T want a spring that has the loop on the end because that contributes to over advancement down low, right? Sounds like I want to run some medium weight springs with no loops?
that will just cause a uniform linear recurve (it just advances a few degrees regularly until it hits the end of the governor... I've used points springs and it's a long slow curve....)

You just need the looped spring that will allow the governor pins to advance almost to the end of the governor, then pic a light spring that will advance through the loop at a 'usable' rate of speed to prevent pinging, but give you all the advance you want at just above the rpm you hold at highway cruise (so if the van does 55 religiously at 2800 rpm... you'r looking for the light spring that will move things along and 'stop' about 3100 rpm..)

it's a real juggling act, and you have to spend a good afternoon with the dial back, spare dizzy, test driving and tuning.... I'm glad I have a dizzy machine... so I don't waste as much gas just 'dialing in' dizzy's in the car...

-D.Idiot
Author:  Reed [ Sun Aug 17, 2008 8:03 pm ]
Post subject: 
I'm off to Niagara falls and New Mexico. Back in a Week!
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