Distributor Rotors

at the beach

at the beach

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Dan Walters discovered a strange parts problem that might effect any of us.

When trying to trace an engine misfire, we were about to replace a rotor when Dan noticed that the two looked different. He ended up chucking a rod the size of a distributor shaft into the lathe and placed the black rotor on it. It fit snugly. Then he moved a cutting tool so that it just made contact with the tip of the rotor.
(pictured below)

Later he removed that rotor and inserted a blue one. He did not move the tool. There was a large gap between the tip of the rotor and the tool. The gap measured .084".
(also pictured below)

Has anyone else noticed variations in rotor sizes supplied for Ford distributors?
 

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TigerBlue

TigerBlue

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Good

Certain standards have been constant over time but others have declined. A .84 gap would.. at the rotor disable a stock points ignition? Assuming an MSD capacitive discharge and fresh plugs? Might not be a problem? Or the problem is disguised, limited or masked by the hyper sparks created.

Thanks for airing this problem. Complete combustion of each particle:eek: of fuel introduced may become more than a competitive issue.
 
C

cadreamn67

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Since you can buy the caps and rotors separately, one would expect that they would all be made to some standard specification. It occurs to me that maybe the Ford specification is just in terms of the air gap between rotor and cap terminal. Since there are two sides to a gap, maybe one needs to always replace the cap and rotor at the same time, with parts from the same manufacturer. (Probably a good idea to replace both at the same time anyway...) That all aside, does anyone know what the gap is supposed to be? Gene
 
X

XTIGERX

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I bet it's made in China.

They seem to just make stuff that appears to look like a particular item and aren't concerned about the materials that are used or quality or that it meets specs, just that it looks like the item. It keeps the masses busy I guess.

I would think parts made in China under control of the OEM would be fine. It's just knock-off replacement items that would be of concern.
 
X

XTIGERX

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Gene.

I'll take a stab at the gap to be similar to the point gap of .016 or .017.

Justin
 
spmdr

spmdr

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The problem continues today!

Standard brand Blue Streak Rotor #FD311

The Ironic thing is, the rotor box says "Superior Quality Automotive Parts"

I would hate to see the inferior parts...

DW
 
michael-king

michael-king

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spmdr said:
The problem continues today!

Standard brand Blue Streak Rotor #FD311

The Ironic thing is, the rotor box says "Superior Quality Automotive Parts"

I would hate to see the inferior parts...

DW
Click to expand...
"Superior Quality Automotive Parts" TM
 
Warren

Warren

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It's also 15 bucks with a limited lifetime warranty . Possibly a house fly's lifetime at O'Reilly auto parts. "Hecho en Mexico."
 
Warren

Warren

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Correction they are 8 bucks and here's a picture of the new vs old POS. You can see the slightly exaggerated false perspective from the camera angle but it's a significant difference. More $ isn't always better.
Do you suppose you'd notice a difference with a Jiggawatt newer super coil?

PXL_20210727_170322447.jpg
 
T

Too Tech

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Warren said:
Correction they are 8 bucks and here's a picture of the new vs old POS. You can see the slightly exaggerated false perspective from the camera angle but it's a significant difference. More $ isn't always better.
Do you suppose you'd notice a difference with a Jiggawatt newer super coil?

View attachment 13984
Click to expand...
What is the part number of the black rotor. I would like to buy one and compare it to what I have
 
0neoffive

0neoffive

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Being a cheap Yanqui, I normally just gently bead blast the older units clean and they are good for another 60K miles. The stubby rotors will manifest as the rpm increases and mimic "point bounce" . . . . .A high energy coil is not always a good thing as some unwanted arc welding can take place inside that crowded cap.
 
Warren

Warren

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It's the El Cheapo at O'Reilly auto parts sorry no p/n. I often used to take a little emery cloth to freshen up a rotor but on Dan W. advice got a fresh one.
 
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