choosing brake drums for 1940 ford

[JSeery]

Hope, do you have a voltmeter? You can check the coil and help ID it if you have a meter.

[hope]

O.K. Later, its too late for today.
Hope

[hope]

Originally Posted by JSeery

Hope, do you have a voltmeter? You can check the coil and help ID it if you have a meter.

JSeery


Yes i do have a meter, but i will have to look up the "meanings" of the reading to see if it will help me.
Hope

[V8COOPMAN]

Hey Leo....Wait patiently until JSeery comes back around to help you through a simple exercise with your meter and that coil to determine just what it is inside. Like Paul Harvey used to say......STAND-BY for more! DD

[bobH]

I'm gonna stick my neck out here, and suggest something that some of the 'techies' here will presumably not like or endorse... That is, why do ANYTHING with those 40 rear drums? Seriously, apply a little common sense. Most of the braking is on the front. The rears do very little. And, if I followed this thread correctly, I think we are discussing changing a drum that is at .125 over. And, some bureaucrat much more recently than 1940, decided that .060 is the maximum 'safe' over. The difference that we are suggesting is 'unsafe', is about .065. Correct? That's on the diameter, correct? And, that's about .030 on the radius (or surface). So, I say, take a good look at that drum, and check to see if there is adequate 'meat' left. I'm betting that on Henry's 1940 drums, there is still lots of meat left. Me thinks that if the goal is to find a drum that meets some .060 spec, we're nitpickin here. As most of us old guys know, we never worried about .125 over, back in the day. (And, to put myself where my mouth is, my own personal pickup, which is 51 years old, has been running one rear drum at .125 over, for the last 40 years. No problems.)

[V8COOPMAN]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by bobH

I'm gonna stick my neck out here, and suggest something that some of the 'techies' here will presumably not like or endorse... That is, why do ANYTHING with those 40 rear drums? Seriously, apply a little common sense. Most of the braking is on the front. The rears do very little. And, if I followed this thread correctly, I think we are discussing changing a drum that is at .125 over. And, some bureaucrat much more recently than 1940, decided that .060 is the maximum 'safe' over. The difference that we are suggesting is 'unsafe', is about .065. Correct? That's on the diameter, correct? And, that's about .030 on the radius (or surface). So, I say, take a good look at that drum, and check to see if there is adequate 'meat' left. I'm betting that on Henry's 1940 drums, there is still lots of meat left. Me thinks that if the goal is to find a drum that meets some .060 spec, we're nitpickin here. As most of us old guys know, we never worried about .125 over, back in the day. (And, to put myself where my mouth is, my own personal pickup, which is 51 years old, has been running one rear drum at .125 over, for the last 40 years. No problems.)

Yeah, 0.125" over works in a pinch. Guys have been cheatin' that way for 75+ years now. But there's a reason for the 60 thou over rule, or like you point-out...0.030" on each surface. At 0.125" over, that "maleable" drum actually is pretty thin, and in a hard, panic stop that drum will actually egg-shape itself. For one thing, it's more prone to cracking. Not only that....if you're making any kind of repeated hard stops or going down a hill, all that additional heat-absorbing material is not there any more to help with normal dissipation once the brakes are released. Brake-fade is imminent. 1/8" over DOES work good...until it doesn't! And heaven help you if you cream some kid and his family's attorney checks your drums. It happens! But what do I know? DD

[JSeery]

Originally Posted by hope

JSeery


Yes i do have a meter, but i will have to look up the "meanings" of the reading to see if it will help me.
Hope

Measure the resistance between the two threaded terminals on the coil (assuming a "can" coil). That will tell you the internal resistance of the coil. A 6v coil should be somewhere in the 1.5 ohm range and a 12v coil should be somewhere in the 3.0 ohm range. Coils can be lower than the 1.5 ohm range, it just determines the required ballast resistor (or no need at all).

You are attempting to achieve a total of approximately 1.5 ohms in a 6v ignition circuit and 3.0 ohms in a 12v circuit. So a ~1.5 ohm coil used with a ~1.5 ohm ballast resistor would work for a 12v system. A ~1.5 ohm coil in a 6v circuit would not require a ballast resistor.

Once you know the primary resistance of your existing coil, it is fairly easy to determine a replacement coil.

[hope]

Stand-by.


All this information has got me in a :"Hold Pattern".


To be continued.


Again Thanks Everybody, in the meantime i've got some some important Honey do list.


Hope.


P.S. On the coil, i don't understand why it gets so Hot and then quits, does it need to be relocated maybe, it now sits on top of the intake near the back?

[1931 flamingo]

"running one rear drum at .125 over, for the last 40 years. No problems"


You must not put on very many miles each year................................
Paul in CT

[19Fordy]

"running one rear drum at .125 over, for the last 40 years. No problems"

WOW! Pretty hard to believe that a knowledgeable car person
would do such a dangerous thing, even for a ride around
the block. I suggest you fix that problem PRONTO.
An accident and lawsuit waiting to happen, especially when you admit
in writing that you know your drums are in such poor condition.

[V8COOPMAN]

Originally Posted by 19fordy

"running one rear drum at .125 over, for the last 40 years. No problems"

wow! pretty hard to believe that a knowledgeable car person
would do such a dangerous thing, even for a ride around
the block. I suggest you fix that problem pronto.
An accident and lawsuit waiting to happen, especially when you admit
in writing that you know your drums are in such poor condition.

"word"! dd

[FlatheadTed]

We changed to metric here in the 70 s so my knowledge is ltd for imperial .Here's a wide 5 I am measuring its near enough NOS ,12" this measure's .o250 (wall ) so going by Bob H post at 30 of each side he's left with .?? ,wall , .