The recent post on distributors reminded me to question the pump drive shaft in my 272. I've measured my Cardone distributor shaft length and it is 6" from the mounting surface. My pump drive shaft doesn't have the retaining clip and the shaft comes out with the distributor when I pull it. I have to reverse the direction of the shaft to unlock it so it will come out of the distributor. I haven't measured the amount the pump shaft goes into the distributor drive shaft, but it isn't much, maybe a quarter inch.  That brings me to ask the questions: How much should the pump drive stick into the distributor shaft? Are there different lengths of the pump drive shaft, or what is the correct length? This shaft has a sharp point on one end, while the other end is somewhat rounded. Thanks for any advice. Gene

I recently had to deal with this question myself.   My new engine is using an ARP oil pump shaft.  These are a lot stronger than the stock shaft.  When I installed it in the block I found it to be too long.  The oil pump wouldn't bolt down all the way causing a bind in the shaft. The ARP instructions warned you to check for this.  I had to slowly grind down the flat end of the shaft to get the clearance right.  I had about .005" end play in my shaft, just enough to relieve the bind and let it turn freely. I think the right depth is as deep as possible without binding. The problem with the rebuilt distributors is a different animal.   With those, the distributor shaft is too short.  This causes the oil pump shaft to not fully engage and does not allow the distributor gear to sit on the block face.  Someone is going to wring off an oil pump shaft at high RPM losing oil pressure with catastrophic results. 

You should fix the problem with the clip missing on your oil pump rod.  You will have to remove the oil pump to fix this.  Luckily the Y Block pump is external. One day you will pull out the distributor and the shaft will fall back into the engine.  You will have to remove the pan and it will cause you a lot of aggravation.  Been there, done that...

I've checked 3 used drive shafts.  About 3/8" of the shaft fits into the distributor but the pointy end goes into the distributor and that is about 1/8" long.  So about 1/4" of engagement effectively.
If you take into account the small chamfer for the hex portion of the distributor shaft, then the shaft is about 13/32" - 7/16" inside the distributor shaft.

Apparently, there are two different shaft lengths:
http://forums.y-blocksforever.com/FindPost137027.aspx



Lawrenceville, GA

Thanks for the information. I have a new shaft and pump gasket on the way from Rock Auto. I just hope that the hex in the distributor shaft isn't the reason that the shaft is trying to twist in the hex.

P.S. If the shaft were to fall into the pan would there be any harm in just leaving it there?

That is surely some nice detail work ...

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Probably no harm as long as it is at the bottom of the pan.  I haven't looked at that.  With a truck or T-bird, if it fell and remained vertical on the oil pickup, that might cause issues if it were to move and be hit by the crank or a rod.  In this case, it may simply be a matter of rotating the crank by hand a few times.  For a car, it could be vertical while resting on the floor of the rear of the pan or it might come into contact with the rotating assembly when it tips into the sump.  If you have a spare pan and shaft, you can investigate.


Lawrenceville, GA

It would be nice if either TED EATON or JOHN MUMMERT could actually find the time to measure and arrive at an optimum rod length (along with minimum tapering length/amount on the DIST end) (ARP).

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One of the distributor cores I have, had planned on using it - but the shaft was obviously bent. How does this happen??

So got me to wondering (always sketchy) is the oil pump drive shaft also prone to bending? I'd expect either to cause rapid wear of distributor bushings and cam wobble (dwell) issues.