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Discussion Starter #1 (Edited)
Distributor Gear Installation Info

Link from OEM replacement instructions:
91173


Link from Ford Racing Performance Parts (pull out to measure end play):

Link from MSD Ignition (push in to measure end play):
https://static.speedwaymotors.com/pdf/547-8585.pdf

Link to entire previous discussion:

351W (TFI also) and 460 distributor compatibility
Spoke with MSD technician about 351W/460 distributor compatibility. He said they get this question a lot and the confusion is with:
1) Pre/post EFI era distributor.
2) Oil pump driveshaft type.

(I'll paraphrase what HE said.) If you're dealing with pre-EFI era distributors, then the two distributors are directly interchangeable after you've swapped the gear. The only difference is, the 460 distributor is slightly taller (external-from engine to cap) and the gear. Supposedly, the 351W distributors have a minor clearance issue with the 460 Edelbrock Victor intake manifolds (and possibly some thermostat housings).

Now if you're dealing with a 351W EFI distributor, then there is a minor implication that is easily addressed. The 351W EFI distributor does have a longer shaft (he didn't know exactly how much longer, but he said less than 1/2"), but the female hexagon drive (on end of distributor shaft) is deep enough to be used with an STOCK oil pump driveshaft. The problem is, no one seems to use the stock driveshaft. If you're using an aftermarket heavy duty oil pump driveshaft (such as ARP and most other brands), the 351W EFI distributor will not fit in the 460 because the driveshafts are a larger diameter (reduced only at hex end). You then have to cut, the difference in length (between the two distributors), off the end of the 351W EFI distributor shaft. This is what we discussed...just thought I'd pass it on.

Link to entire previous discussion:
Ford 385 Series Engine Builders Forum: 460 EFI distributor
 
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Danny that Tech article from Ford Racing would be a nice addition to the engine build archives!!!... Thats great distributor information for anyone building or working on a BBF.
 

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Discussion Starter #3 (Edited)
Distributor Gear Roll Pin Information

I use a 3/4" long coiled roll pin from McMaster-Carr. Type 420 Stainless Steel— More corrosion resistant than plain steel and magnetic. Rockwell hardness is C46-C55. Strong enough for me.
http://www.mcmaster.com/#95765a339 (1/8" Diameter)
https://www.mcmaster.com/#95765a413 (3/16" Diameter)

There is a significant durability difference between a 'shear pin' and a 'coiled roll pin' (however, both are meant to shear if overloaded beyond their rated specs). I've seen some new distributors assembled with this weaker shear pin:


Which I replace with this aforementioned 'coiled roll pin':
 
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Discussion Starter #4 (Edited)
Steel Distributor Gears

Mallory ignition offers alloy steel distributor drive gears for use with proferal (cast) flat tappet hydraulic/mechanical camshafts and austempered ductile iron roller camshafts. Available for original equipment, and other aftermarket distributors with a shaft size of .531" (#29420). I have personally used this steel distributor gear on two hydraulic flat tappet equipped engines for six years (one being a daily driven vehicle with a HV oil pump) without any problems. Six years later, the only wear shown is a bright, shiny mesh pattern. Seems like Mallory Ignition & Crane Cams have us well covered with compatible steel distributor gears for our '385' engines:

Mallory Ignition alloy steel gear #29420 (replaces #28653); for use with cast flat tappet hydraulic/mechanical camshafts and austempered ductile iron roller camshafts.
http://www.carid.com/images/mallory/info/catalogue.pdf (page 35)

Crane Cams heat treated gear #52971-1; for use with induction hardened steel and carburized steel camshafts.
http://www.cranecams.com/product/cart.php?m=product_detail&p=25340 (It is steel, not iron.)
 

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Discussion Starter #5
Sheared Distributor Gear Pin Information

This was a great post by Paul Kane describing the 'installed thrust clearance' (of the distributor gear). This is measured by mocking up the distributor in the engine block with the timing cover off.

Paul Kane said:
If you are shearing pins in your Ford dizzy, it is MUCH more likely due to improper distributor thrust clearance than anything else in the world. Not likely thick oil, oil pump loading, etc. like many people seem to think, meaning that while lesser pumps or thinner oil may alleviate the problem, the culprit of the problem probably has not been addressed (but should be).

There is a distributor shaft end play spec of .020" and an installed clearance spec of less than .010" between the bottom of the dizzy gear and the block's dizzy gear thrust boss (the pad that the dizzy gear rides on once the distributor is installed). Few people understand Ford's reasoning behind the obscure specification and therefore dismiss it.

The reason for these spec is because as the distributor is turned by the cam gear, it is thrust downward against the dizzy's thrust boss in the block. If the shaft end play and boss clearance are out of spec (too much boss clearance/not enough end play), the dizzy gear does not ride on the boss but instead is floating in mid air all the while being thrust downward by the turning of the gear.

Eventually, the dizzy gear roll pin shears downward because the spec's were not set by properly measuring/installing the dizzy gear and/or shimming the underside of the dizzy gear to take up the slack between the boss and gear.

To say that the Ford engines randomly shear pins rotationally is a fallacy which is assumed by those that are not familiar with the detailed workings and necessary specifications of these engines. Their fix is usually to drill oversize and put in a bigger pin though the gear. :roll: The joke about such an approach is that this is a band-aid fix that may or may not end the pin shearing, because more than likely the root of the problem has not been corrected.

Here is a picture of the dizzy gear thrust boss in the block:


If you look in the mirror's reflection in the above photo, you will see just the lightest wear (from the bottom of the dizzy gear) against the top of the boss. This is exactly how the wear pattern should look. If you have more wear, the block gets chewed up; if you have NO wear, the gear is floating and you are shearing pins. Paul
 
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Excellent info on the 351W EFI dizzy. I have been on a search for a 460 EFI distributor with TFI mounted without external wring. Don't 351M/400 share the same distributor as the 429/460? If so, this would mean that 351M/400 motors could use the same modded 351W.
 

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Discussion Starter #7
Monstermiler said:
Excellent info on the 351W EFI dizzy. I have been on a search for a 460 EFI distributor with TFI mounted without external wiring. Don't 351M/400 share the same distributor as the 429/460? If so, this would mean that 351M/400 motors could use the same modded 351W.
Thanks.
Yes, the 351M/400 use the exact same distributor as the 429/460, however, the timing advance curve is different.
 
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