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Ok one last check. I got the dizzy in the motor and I can get an .011 feeler gauge between the gear and the thrust surface.

Is that too much?
If the timing cover and timing chain are removed from your engine and you are able to grab the distributor shaft to pull it downwards while checking your measurement, then yes, the 0.011" clearance is excessive. At most it should be about half that.

Even though you are getting the correct 4.038" measurement in a free-standing state with that shaft pulled out, your final dimension (ie, distributor gear thrust boss clearance) will vary from block-to-block. Why? Becasue these are production parts, let alone any high mileage wear and tear. Adjust thrust boss clearance accordingly to ~0.005" and you'll be good to go.

SIDEBAR TO ALL: If your distributor gear thrust clearance is set correctly you will not shear pins! Roll pin shearing is not "the HV pump's fault" or due to "too much oil pressure" since 100+ psi not a problem with a correctly setup drive system (many big power engines run in the 100+ PSI without issue). The distributor gear is thrust downward as it is being turned by the helical cut gears and so when the distributor gear is too high on the shaft and floating above the thrust boss, the pin gets sheared downward (not rotationally). The downward thrust of the drive system is far greater in load than any amount of oil pressure even poissible in these engines. Set your thrust boss clearance correctly and the pin shearing will go away and you can keep the single pin which Ford designed that way for a good reason.
 

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Discussion Starter · #23 ·
Ok thanks a bunch good info. So I tweaked on it a little more and while pulling it down a .004 feeler gauge mived smoothly within and a .005 had a little drag on it. So I should be good there right?
 

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Ok thanks a bunch good info. So I tweaked on it a little more and while pulling it down a .004 feeler gauge mived smoothly within and a .005 had a little drag on it. So I should be good there right?
Did you do the check with the distributor clamped down in place? If not check it again.








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Crap maybe its a little tighter than that still .003 moves smoothly. This is some tedious stuff.
The thrust surface on the gear should ride on or just above the thrust surface on the block.

A few thou above as paul noted is OK.

The clearance in the dizzy shaft collar to body allows the gear to move up as things get hot and expand.







Scotty J. "AKA" The "Mad Porter"
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Discussion Starter · #29 ·
Well I'm back. :cautious: when I drilled the hole for the pin it moved apparently. Now its either touching or less than .001. This dizzy now has 2 holes drilled in it even though they are not at the same height. Am I sol? Gotta buy a new dizzy? Or do you think I can safely try again?

Thanks!
 

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There is no reason to have this be so complicated.

If when the distributor is dropped in and locked down the gear is touching the thrust surface AND you can move the shaft up 20 to 30 thousandths until the collar above the gear contacts the housing... RUN IT !!!





Scotty J. "AKA" The "Mad Porter"
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There is no reason to have this be so complicated.

If when the distributor is dropped in and locked down the gear is touching the thrust surface AND you can move the shaft up 20 to 30 thousandths until the collar above the gear contacts the housing... RUN IT !!!





Scotty J. "AKA" The "Mad Porter"
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Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
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I might have missed what the average depth of the thrust surface from distributer mounting surface? For an assembled and installed engine, is it acceptable to simply lower the gear to make up for worn thrust surface?
Thanks
 

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I might have missed what the average depth of the thrust surface from distributer mounting surface? For an assembled and installed engine, is it acceptable to simply lower the gear to make up for worn thrust surface?
Thanks
That was silly question, as lowering gear to make up for worn thrust surface will mess up cam alignment. What is acceptable practice for correcting worn thrust surface in otherwise healthy engine?
 

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If you're this concerned about tooth to cam on the distributor, paint some white grease on all of the distributor teeth. Drop it down and lock it in place. Spin the engine over 1 time.. in the direction it turns when it's running, it's not a rear end so no back lash to account for here. Pull the distributor and check the wear pattern.. if it looks good RUNNIT!! If it needs to go up get a shim from a Chevy distributor kit and shim it up a fuzz. You shouldn't have to fiddle about with it....
 

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If you're this concerned about tooth to cam on the distributor, paint some white grease on all of the distributor teeth. Drop it down and lock it in place. Spin the engine over 1 time.. in the direction it turns when it's running, it's not a rear end so no back lash to account for here. Pull the distributor and check the wear pattern.. if it looks good RUNNIT!! If it needs to go up get a shim from a Chevy distributor kit and shim it up a fuzz. You shouldn't have to fiddle about with it....
Long story short, last guy that worked on my engine before me and last builder installed a Motorcraft 12127CA with gear relocated incorrectly, I still have the dizzy and it measures about 4.122 dropped, about 4.038 up. Pulled cap and it was driving assembly through cap/dizzy. I ran this for about 3000 miles before pulling engine for rebuild because of vibration, etc, etc. Anyway, when I pulled dizzy at same time I pulled engine I noticed a metal shaving on the pad, mentioned it to machine shop/engine builder and was told it looked ok.
I installed a new Pertronix after rebuild and was having issues with an Igniter III after engine warmed up, ended up replacing with another new Igniter II with new bronze gear, only had engine break-in and 40 miles, still have the bronze gear with 40 miles on it sitting in my garage.
Got to reading this thread and decided to take a look at removed Motorcraft and bronze gear with 40 miles, good chance I have an issue.
I have Mag Trigger Pertronix on order because I need to retard timing at start for warm engine, can’t retard more than 4 degrees with an Ignitor II, so this weekend I’ll pull my Ignitor II dizzy with 458 miles and measure Thrust pad depth. Then try to figure out how much of a shim I need. I already know my gear is being pulled down too far by the wear pattern on the 40 mile bronze gear.
Thanks
 

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Long story short, last guy that worked on my engine before me and last builder installed a Motorcraft 12127CA with gear relocated incorrectly, I still have the dizzy and it measures about 4.122 dropped, about 4.038 up. Pulled cap and it was driving assembly through cap/dizzy. I ran this for about 3000 miles before pulling engine for rebuild because of vibration, etc, etc. Anyway, when I pulled dizzy at same time I pulled engine I noticed a metal shaving on the pad, mentioned it to machine shop/engine builder and was told it looked ok.
I installed a new Pertronix after rebuild and was having issues with an Igniter III after engine warmed up, ended up replacing with another new Igniter II with new bronze gear, only had engine break-in and 40 miles, still have the bronze gear with 40 miles on it sitting in my garage.
Got to reading this thread and decided to take a look at removed Motorcraft and bronze gear with 40 miles, good chance I have an issue.
I have Mag Trigger Pertronix on order because I need to retard timing at start for warm engine, can’t retard more than 4 degrees with an Ignitor II, so this weekend I’ll pull my Ignitor II dizzy with 458 miles and measure Thrust pad depth. Then try to figure out how much of a shim I need. I already know my gear is being pulled down too far by the wear pattern on the 40 mile bronze gear.
Thanks
I should start out saying I’m just trying to learn how to set up my distributor to get more than a few hundred miles out of a new bronze gear. Thrust pad measures 4.034”, extended distributor shaft 4.031”, pushed shaft about 4.005+”. Used white grease on new gear and rotated a hair more than once, looks like contact high on one side of teeth and low on other.
haven’t started engine yet. Thanks
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