Distributor lock collar...what's the point?

I'm using a lock collar on the MP distributor in my roller cam 440 because it was recommended. My question is...why? Why is this not needed when using a flat tappet cam?

Also, the 0.010" clearance between the collar and the top of the drive gear is almost impossible for me to set. When I use a 0.010" feeler gauge, I'm setting it lop sided because I can only slide it under one side of the collar. Also, IIRC the distributor shaft has some up and down play. Is that normal?

Thanks

I use one on my flat tappet. The purpose is to prevent the intermediate shaft oil pump drive gear from climbing up the vertical slop on the distributor shaft, which affects ignition timing due to the slant of the gear teeth. The lock essentially eliminates/reduces the amount of slop that the gear can climb.

Don't know why there might be a difference tween roller and flat cams.

My method of setting the collar is to install it with a bit of tension, LOW on the shaft, but not so much that it's locked to the shaft. Then install and bolt down the dist. Unbolt, remove dist, then lock down the collar in that position. Blue loctite on the set screw.

Also alleged by some to lessen distributor shaft gear wear on the bronze gears typically used when running a roller cam.

Use 2 feeler gauges one on each side.

I would drive out the lower shaft roll pin & add some flat shims above the plastic collar to reduce the axial play to .005". speedway mtrs has an assortment of em in a kit for cheap, you want shims that are flat with no sharp edges like regular washers have on the ID/OD on one side which the ones in their kit are flat then reinstall the plastic collar then snug the lower metal add on collar in question on the shaft "snug" close to the bottom & install the intergear & the collar will be pushed up then remove the intergear & raise the collar up a hair from that position & tighten it & reinstall the intergear. when done twist the rotor back & forth lightly (not enough to get into the springs) & see how much rotational slop is left as that is what is to be eliminated. May need to weld or peen the lower tang for a better fit into the intergear notch if needed.

Thanks again guys. I currently have it locked on the distributor but it's slightly lop sided. I'm guessing this thing isn't absolutely necessary unless you're racing?

reduce the axial play to 5 thou & you might not even need it.

Yes, it certainly would. That's a brilliant observation on someone's part.

I'm using the coated gear instead of the bronze

I've been told to slightly snug the collar onto the distributor shaft and then install the distributor into the motor and lock it down, rotate the motor over several revolutions and then remove the distributor and tighten the collar

Thanks Cab

I should have included to slide it down far enough on the distributor shaft so it has to hit the oil pump drive when tighten
down by the distributor hold down bracket

Yep



And don't do like I did the first time, didn't have it snug enough on the shaft and it slid off and sounded like a pin-ball machine going all the way down to the oil pan.

I would like to know where you buy the locking collar. Do you use a set screw type or the split or double split. Next thing , The distributor shaft is not the diameter of any that I found on line. Do you bore the collar out to the shaft size? or where do you purchase the correct size.

1/2" double split shaft collar works for me. A good hardware store or industrial supplier will have them. Graingers or McMaster carr for sure. Home Depot probably not.

Thanks for your input GomangoCuda. Why I asked the question was that the collars I found on line were either 1/2" or smaller 7/16". The shaft on my distributor is smaller than 1/2" and a lot bigger than 7/16", Maybe the double split 1/2" collar might not be concentric around the shaft but apply enough clamping force to hold. It looks to be .010 - .012 under 1/2" Anyone else?

What is a distributor?

Andy, my distributor hole plug looks similar to yours but doesn't have that black thing on top. By the way , whats in your water?

this one clamps fine on a .4885 dist shaft. I don't remember if I got it at grainger or mcmaster/carr.

Wow, You guys over complicate things. Here's what I've been doing since the 70's, all you need is a short piece of rubber hose 1/2" ID. Slip it over the shaft, tighten down the distributor, DONE. The hose will keep the intermediate shaft from dancing around and you'll have steady timing instead of a timing mark jumping around 5-7 degrees.

that's (way) too easy. good tip!

maybe i'm missing something here? the helical drive gear is forced DOWN against the bushing by oil pressure. forced down HARD.

Not on a big block, it's forced up by the counter clockwise rotation, the small block it's forced down by the clockwise rotation, that's why this isn't needed on a small block.

That's interesting, guess I wasted my money on collars.
Hadn't gotten around to installing on my SB.
You saved me the aggravation

It worked for me on my SB, timing is nice and steady now