The Ford Barn

Bob Bidonde · 03-14-2018, 01:17 PM

Play between the post in the distributor casting and the hole in the center of the upper plate affects the point gap. Does anyone know what the clearance is by design?

Kurt in NJ · 03-14-2018, 01:22 PM

The original upper plate has a ground hole, with unworn casting, nos plate it was less than .004 , with aftermarket reproduction was .020 on one, another was .012 t

CWPASADENA · 03-14-2018, 11:06 PM

The plate must fit the distributor with very little clearance. I would say .001 - .002 should be plenty. You just do not want the plate to bind as it is rotated.

Any slop will result in changing the point setting.

I have seen replacement plates with .010 - .020 oversize in this hole. One replacement plate looked like it was laser cut and left what looked like saw teeth around the inside of the hole.

NOS and NORS plates usually will fit nice and snug on the distributor body boss resulting in no change in point gat as the plate is moved back and forth.

My opinion,

Chris W.

Brentwood Bob · 03-15-2018, 12:29 PM

I have tried stakeing in the top side of the upper
Plate to jury rig. Also deformed the ears to fit tighter in the outer perimeter groove.

Bob Bidonde · 03-15-2018, 01:06 PM

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Considering the 0.004 spread in the stock point gap range, my expectation is that a NOS upper plate made to Ford's spec would have a fit with less than 0.004 clearance.

Lets say the an excellent distributor build has the characteristics:
> Upper plate to distributor casting clearance is 0.002";
> Cam fit to shaft plus cam lift has a total variation of 0.002";
> Fit of the shaft into it's bushings is 0.002".
Then expecting the points to have a gap in the range of 0.018" to 0.022" is unrealistic. I doubt that anyone is running a stock distributor this neat.

I am going to measure the parts in the recently rebuilt distributor I am running in my 190A. Depending on the actual fits I find, I will open the point gap accordingly.

It will not surprise me if the point gap winds-up at 0.028" to 0.032" with the expectation that actual working gap will be in the 0.018" to 0.022" range. This should give the coil more milliseconds to build a field.

More to follow on this topic. I need to experiment!

03-14-2018, 01:22 PM	#2
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,157	Re: Upper Plate To Distributor Casting The original upper plate has a ground hole, with unworn casting, nos plate it was less than .004 , with aftermarket reproduction was .020 on one, another was .012 t

03-14-2018, 11:06 PM	#3
CWPASADENA Senior Member Join Date: May 2010 Location: PASADENA, CA Posts: 1,884	Re: Upper Plate To Distributor Casting The plate must fit the distributor with very little clearance. I would say .001 - .002 should be plenty. You just do not want the plate to bind as it is rotated. Any slop will result in changing the point setting. I have seen replacement plates with .010 - .020 oversize in this hole. One replacement plate looked like it was laser cut and left what looked like saw teeth around the inside of the hole. NOS and NORS plates usually will fit nice and snug on the distributor body boss resulting in no change in point gat as the plate is moved back and forth. My opinion, Chris W.

03-15-2018, 12:29 PM	#4
Brentwood Bob Senior Member Join Date: May 2010 Location: brentwood, ca Posts: 4,241	Re: Upper Plate To Distributor Casting I have tried stakeing in the top side of the upper Plate to jury rig. Also deformed the ears to fit tighter in the outer perimeter groove.

03-15-2018, 01:06 PM	#5
Bob Bidonde Senior Member Join Date: May 2010 Location: Long Island, NY Posts: 3,463	Re: Upper Plate To Distributor Casting Sponsored Links (Register now to hide all advertisements) Considering the 0.004 spread in the stock point gap range, my expectation is that a NOS upper plate made to Ford's spec would have a fit with less than 0.004 clearance. Lets say the an excellent distributor build has the characteristics: > Upper plate to distributor casting clearance is 0.002"; > Cam fit to shaft plus cam lift has a total variation of 0.002"; > Fit of the shaft into it's bushings is 0.002". Then expecting the points to have a gap in the range of 0.018" to 0.022" is unrealistic. I doubt that anyone is running a stock distributor this neat. I am going to measure the parts in the recently rebuilt distributor I am running in my 190A. Depending on the actual fits I find, I will open the point gap accordingly. It will not surprise me if the point gap winds-up at 0.028" to 0.032" with the expectation that actual working gap will be in the 0.018" to 0.022" range. This should give the coil more milliseconds to build a field. More to follow on this topic. I need to experiment! __________________ Bob Bidonde Last edited by Bob Bidonde; 03-15-2018 at 01:13 PM.