Author Topic: Point Distributors: Using a spring tension gauge!!!  (Read 3534 times)

Online goodfellow

  • RestroLibrarian
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 9291
  • location: Northern Virginia
Point Distributors: Using a spring tension gauge!!!
« on: June 19, 2010, 06:24:01 AM »
Although many of the older GH members know about this procedure, many of you younger folks probably have never worked with an old fashioned "point type" distributor. Here is how the old timers used to test the "point pressure" on a distributor lobe.

We all know that the dwell angle is the most basic setting on "point" actuated distributors, but those points had many weaknesses. Even though they may not have been pitted after 3000-5000 miles (the recommended change interval), many times the point spring was causing ignition problems such a "misses" and "backfires".

One of the most crucial items for this diagnostic was a distributor tester AND a "Point Spring Tension Gauge"







Look at this vintage Chrysler "Solar Spark Ignition" distributor form the ealry 1950's



The points tested OK with dwell, resistance and RPM on my Distributor Tester, so the last test requires a spring pressure test. This is where the gauge comes in.
The point rubbing block is positioned in the middle of a flat section of the distributor lobe. This assures that the points are totally closed. The gauge then hooks to the point tension arm and is pulled until the points just start to open -- at that point a reading in ounces is taken from the gauge. In our case it's 24oz.





Next the proper car model and year are scrolled and found on the Distributor Tester and the "Spring Tension" reading is noted -- in this case the reading is 17-20oz.





This variation (24oz vs. the OEM recommended 17-20oz) tells us that the tension is too high and that the new point set will most likely wear prematurely and may cause ignition problems quite early because the wooden rubbing block is pushing too hard on the distributor shaft lobes. The remedy is to realign the points, readjust the springs, or subsitute another set. In any case -- the Spring Tension gauge was an invaluable tool for bench testing distributors of the time.

Offline Uncle Buck

  • Site Owner/ Founding Spammer
  • Administrator
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 8050
  • location: Kansas-Flyover Country!
  • The name of my small shop is the Skunkworks!
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #1 on: June 19, 2010, 06:34:13 AM »
That was a total lesson for me. Many times I have a basic knowledge of some of the things you post, but this spring tension lesson was all new territory for me. I grew up with point distributors and have decent understanding of them, and how they work. With that said, I would call that more of an advanced tutorial.
You boys better hold on cause i'm gonna have to stand on it!

Offline wilbilt

  • Hero Member
  • *****
  • Join Date: Jun 2010
  • Posts: 1459
  • location: Honcut, California
  • Trailer Trash
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #2 on: June 19, 2010, 06:40:49 AM »
Good information, goodfellow.

We had a distributor tester in my high school auto shop similar to yours. I would get frustrated by the points floating in my '67 Chevelle, and increase the spring tension while checking the distributor to eliminate the float.

Of course, this caused the rubbing block to wear out quickly. The stock points were junk, but the Blue Streak brand was a bit better. At my young age, I never thought about using a tension gauge.

I also didn't realize the points effectively acted as a rev limiter for the 396 big block. Those engines in stock form were prone to valve train problems at higher RPMs.  I learned this after breaking several valve springs, punching a pushrod through a rocker, and eventually destroying the engine when the head of an exhaust valve hit the piston, broke off and went through the cylinder wall.

That tension gauge could have been very important if I had only used it.  :-[
-- Garageless in Northern California since 1985

Online goodfellow

  • RestroLibrarian
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 9291
  • location: Northern Virginia
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #3 on: June 19, 2010, 06:56:16 AM »
.......I also didn't realize the points effectively acted as a rev limiter for the 396 big block. Those engines in stock form were prone to valve train problems at higher RPMs.  I learned this after breaking several valve springs, punching a pushrod through a rocker, and eventually destroying the engine when the head of an exhaust valve hit the piston, broke off and went through the cylinder wall.

That tension gauge could have been very important if I had only used it.  :-[

LOL -- Damn Will, you must have really pushed that 390 mill. Were you racing it?

Offline wilbilt

  • Hero Member
  • *****
  • Join Date: Jun 2010
  • Posts: 1459
  • location: Honcut, California
  • Trailer Trash
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #4 on: June 19, 2010, 07:05:08 AM »
.......I also didn't realize the points effectively acted as a rev limiter for the 396 big block. Those engines in stock form were prone to valve train problems at higher RPMs.  I learned this after breaking several valve springs, punching a pushrod through a rocker, and eventually destroying the engine when the head of an exhaust valve hit the piston, broke off and went through the cylinder wall.

That tension gauge could have been very important if I had only used it.  :-[

LOL -- Damn Will, you must have really pushed that 390 mill. Were you racing it?

A 396, and not "racing", just doing what high schoolers do with cheap gas, too much HP, and too little experience.
-- Garageless in Northern California since 1985

Offline Elroy

  • "Moron"
  • Super Hero
  • ******
  • Join Date: Jun 2010
  • Posts: 2559
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #5 on: June 19, 2010, 03:50:46 PM »
Those engines in stock form were prone to valve train problems at higher RPMs.  I learned this after breaking several valve springs, punching a pushrod through a rocker, and eventually destroying the engine when the head of an exhaust valve hit the piston, broke off and went through the cylinder wall

Elroy ventures to say a bunch of them bit the dust like that
I met Elroy years ago, I was not at all impressed with him, the guy was like a talking potted plant! A real Moron.

Elroy exists in a demented third person world that is void of Bull Shit and lies.

Offline Frank Elson

  • Sr. Member
  • ****
  • Join Date: Jun 2010
  • Posts: 251
  • location: Lancashire, United Kingdom
    • www.lrm.co.uk
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #6 on: June 19, 2010, 03:56:10 PM »
whoo hoo I am SO glad you're still  around to tell us how the Jag rebuild goes GF ...
Best Cheers

 Frank
    ---------
    I !__[_]|\___
    I ____|"_|"__|/   
     "(o)======(o)"     1997 Range Rover 4.6 HSE

Online J.A.F.E.

  • Alien Wizard Of Odd
  • Global Moderator
  • Knows what a screwdriver is
  • *****
  • Join Date: Jun 2010
  • Posts: 6061
  • location: About 28000 Light Years from the Center of the Galaxy. At the moment.
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #7 on: June 19, 2010, 05:08:16 PM »
I like points ignitions but in truth the single best thing to happen to internal combustion engines was getting rid of them.

They likely were the single most failure prone part and the one requiring the most maintenance.
As alien as it gets.

Quote
Whatever he is it is seriously unpleasant.    No moral compass at all, no thoughts, no guilt or obligations beyond personal desires of the moment and no debts recognised if he already has the product.
                                   

Live long and 42.

Offline wilbilt

  • Hero Member
  • *****
  • Join Date: Jun 2010
  • Posts: 1459
  • location: Honcut, California
  • Trailer Trash
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #8 on: June 20, 2010, 06:42:05 AM »
I like points ignitions but in truth the single best thing to happen to internal combustion engines was getting rid of them.

They likely were the single most failure prone part and the one requiring the most maintenance.

Yes and yes, I guess.

However, if your PCM, ECM, Igniton module, etc., goes away on a rainy night, you can't fix it with a screwdriver and a nail file.
-- Garageless in Northern California since 1985

Online goodfellow

  • RestroLibrarian
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 9291
  • location: Northern Virginia
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #9 on: June 20, 2010, 06:54:16 AM »
I agree with J.A.F.E. -- but on a hobby car dealing with points and dialing in the dsitributor on a Sun or Allen machine is just part of the history. I have used points and standard ignitions in all my old cars because it's fun to use the old analog analyzers.

Also, even with the analyzers, it's still quite a challenge (almost an art) to do a precision tune up on a point type ignition system with a carburetor induction system. There are a lot of variables. It's almost becoming a lost skill set.

Offline Elroy

  • "Moron"
  • Super Hero
  • ******
  • Join Date: Jun 2010
  • Posts: 2559
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #10 on: June 20, 2010, 07:06:00 AM »
It's actually rather simple (kind of)

Points wide, plugs narrow.

The rubbing block on the points will wear in so setting the points wide (small dwell angle) will allow the dwell to drift in to where it should be.
A narrow plug is also easier to light off and they too will "wear in". Surely there is more to it but points work fine if adjusted properly. Elroy is also glad he doesn't have any to mess with.
I met Elroy years ago, I was not at all impressed with him, the guy was like a talking potted plant! A real Moron.

Elroy exists in a demented third person world that is void of Bull Shit and lies.

Online goodfellow

  • RestroLibrarian
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 9291
  • location: Northern Virginia
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #11 on: June 20, 2010, 07:07:34 AM »
Welcome Elroy!! I like the new avatar -- a classic script

Offline Elroy

  • "Moron"
  • Super Hero
  • ******
  • Join Date: Jun 2010
  • Posts: 2559
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #12 on: June 20, 2010, 07:09:34 AM »
Welcome Elroy!! I like the new avatar -- a classic script

You didn't like Elroy's hat??
I met Elroy years ago, I was not at all impressed with him, the guy was like a talking potted plant! A real Moron.

Elroy exists in a demented third person world that is void of Bull Shit and lies.

Online goodfellow

  • RestroLibrarian
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 9291
  • location: Northern Virginia
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #13 on: June 20, 2010, 07:10:39 AM »
Welcome Elroy!! I like the new avatar -- a classic script

You didn't like Elroy's hat??

Loved the old "Elroy", but change is good!!

Offline Elroy

  • "Moron"
  • Super Hero
  • ******
  • Join Date: Jun 2010
  • Posts: 2559
Re: Point Distributors: Using a spring tension gauge!!!
« Reply #14 on: June 20, 2010, 07:18:40 AM »
Change is good and we have a nice clean slate to work with
I met Elroy years ago, I was not at all impressed with him, the guy was like a talking potted plant! A real Moron.

Elroy exists in a demented third person world that is void of Bull Shit and lies.

The Garage Gazette

Re: Point Distributors: Using a spring tension gauge!!!
« Reply #14 on: June 20, 2010, 07:18:40 AM »

Tags: