msd distributor in 460 block

i have an msd distributor thats suppose to be for a 429/460 block,but the bottom of the shaft below the gear measures .510 dia.,and my block is unknown!dia.msd list the pro billet that fits all 351c-460,do they have the .530 dia?and what about the 351w is it a .510 dia?
bad calipers!

What’s the part # of the MSD distributor in question?

it shows a .530 shaft dia,but this is .510.bought it used,so maybe they changed the shaft out.can you buy the correct shaft from msd?or will the .510 be ok in the block pilot(probably not!)

https://www.summitracing.com/parts/msd-8580/make/ford

The MSD dizzy utilizes a gear for a 0.530” diameter shaft. The distributor shaft locator hole in the Thrust Boss of the block is about 0.515”. So the MSD shaft steps down from 0.530” (where the gear is) to 0.515” (to fit the locator hole in the block).

dove-a block is at least .530,as oil primer shaft is .530 and fits nice.i will have to call msd(ugh!)

not that anybody is online here,and everybody is on fb,i called msd today and they said the drawing for the 8577 distributor shows a .514 dia below the gear.tech said that it does not pilot on the block and is only there to turn the oil pump.there must not be enough load on the gears to require it to be supported by the block hole.learn something every day!who new!
but i wonder if with high volume oil pumps turning 7,000 or more,is that the main load/wear on the gear.

Paul Kane wrote:The MSD dizzy utilizes a gear for a 0.530” diameter shaft. The distributor shaft locator hole in the Thrust Boss of the block is about 0.515”. So the MSD shaft steps down from 0.530” (where the gear is) to 0.515” (to fit the locator hole in the block).

EXACTLY ... just like an original Ford distributor.

hbstang wrote:dove-a block is at least .530,as oil primer shaft is .530 and fits nice....

Then someone must have modified that hole in your engine block. I've never come across a 385 Series cylinder block with a 0.530" receiver hole.  To be sure I went and spot-checked several blocks here at the shop, and of the ten blocks that I checked none would take a 0.530" diameter shaft.  If your block indeed has a 0.530" hole in the Thrust Boss then my advice is to either, 1) bush it back down to spec, or, 2) utilize a distributor shaft that is correctly sized for a 0.530" receiver hole so that you get support at both ends of the drive shaft rather than only at the aluminum distributor housing which is several inches away.

hbstang wrote:...i called msd today and they said the drawing for the 8577 distributor shows a .514 dia below the gear. tech said that it does not pilot on the block and is only there to turn the oil pump...

If that were true then why did Ford make the hole 0.515" and the end of the distributor shaft 0.514" so as to effectively support the shaft at both ends?  Also, why didn't ford simply have the distributor shaft end exactly at the bottom of the distributor gear and have the oil pump shaft reach up into the shaft at the gear location? The fact is that MSD's own drawing for the 8577 distributor reduces to 0.514" because a 0.530" shaft will not fit the block as Ford machined it, and note that their shaft diameter (0.514") accommodates the block's bore diameter (0.515") as though intended to provide that support.

The "tech" at MSD is spit-balling, or he's got his head up his ass.  Or possibly both.

+1 The MSD tech is STUPID. "only there to turn the pump" is as dumb as it gets. The distributor gear pushes AWAY from the cam in operation and excessive "play" in the block would wipe out the gear in MINUTES.

CORRECTION,i am not sure what size the block pilot is.i have to make something that is .515 to check it,but randy is right,i think it does need to pilot in the block to keep gear in place.