Oil Pump driveshaft and Dart Little M with 400 mains

[Tokyo Torquer]

I have a problem with oil pump drive shaft hitting the inside of my new Dart Little M block at the end of the shaft near where it engages the end of the distributor. I have 2 stepped driveshafts (.391 to. 481 step).. an ARP and a Melling IS55E. The ARP shaft jambs in there easily and hard to get back out. The Melling shaft barely just hits, but you can feel it touching. The shortblock is all assembled.

In the pic below you can see that the end of the shaft lays right up alongside the block casting down in the distributor hole. I dont think this is the problem that Dart refers to in the tech note below as it has nothing to do with the size of the hole.

OOPs.. they say I need 10 posts to post a pic and I only have 5.

Any advice appreciated on the oil pump driveshaft problem.

thanks

mike
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Here is the Dart Tech Note:
OIL PUMP DRIVESHAFT
On blocks with 400 main size you MUST use a 400 oil pump shaft which has a diameter of .425”. If you are using an after market HD shaft or a 350 shaft, which are .481” diameter, you MUST machine the center of the shaft to .425” to clear the hole in the block. If this is not done, you may experience oil pump and/or distributor gear problems. The 400 main blocks have a hole .062” smaller than a 350 so the shaft hole will not break through to the rear main bore.

[Tokyo Torquer]

Now it should let me post the picture of the problem. Here it is..

http://memimage.cardomain.com/ride_images/1/2759/821/6895410126_large.jpg

any advice appreciated.

[CNC BLOCKS]

I fit just fit up a oil pump, oil pump shaft and dist. on a Little-M with 350 mians and the bore size of the shaft hole maybe smaller on your 400 main block.

I also measured from the top of the dist. hole in the block down to the the bottom of the step and I came up with 3.725

[BIG CHIEF]

This is the information on the first page of our instruction sheet that comes with the block. I have also attached a copy of the sheet for your review. Let us know if you need anything else?

OIL PUMP DRIVESHAFT
On blocks with 400 main sizes you MUST use a 400 oil pump shaft which has a diameter of .425”. If you are using an after market HD shaft or a 350 shaft, which are .481” diameter, you MUST machine the center of the shaft to .425” to clear the hole in the block. If this is not done, you may experience oil pump and/or distributor gear problems. The 400 main blocks have a hole .062” smaller than a 350 so the shaft hole will not break through to the rear main bore.

Note: Be sure to check distributor to oil pump shaft clearance with distributor, intake manifold and oil pump installed on block.

[Tokyo Torquer]

Thanks Big Chief.. the tech note is the same I included in my original post and I believe refers to the size of the hole (at the pump end) due to the bigger 400 journals, but that is not where I have interference, it is the other end of the driveshaft where it is flush up against the bulkhead/ block wall right underneath the step in the distributor hole.

mike

[BIG CHIEF]

Mike,

I have sent out all your information and pictures to our machining facility to determine what the exact issue may be. I should know something today for you. Do you have an e-mail address I can e-mail you direct at when we have a solution?

Best Regards,

Mike

[Tokyo Torquer]

Thanks so much, Mike. I have been playing with it today trying to find the exact issue. My priming tool fit on the pump shaft with no problem, but you could feel it rubbing when you turned the pump shaft, I just could not see where it was rubbing since the shaft was so close to the wall of the block (I have since learned that is they way they normally are). I took the measurements I got from Carl Hinkson of how far the step was machined down in the distributor hole and it was 3.75" from the top of the distributor hole in the block. I beleive that is correct and there are no machining issues with the block and it is as it is supposed to be.

So what I did was just spin the pump drive shaft until a shiney line around the shaft showed up to tell me where it was rubbing. I found two spots.. One is there is a very small ridge right where the machined step is inside the distributer hole.. it can probably be addressed with a long screw driver and a tap with a hammer or with a few strokes of a file. The other spot is the rear main cap nut.. we are using the washer with the flat side and the smaller nut, but when I turn the block right side up on the stand, and when the pump shaft falls down onto the pump, it just barely hits the shoulder of the nut and not only cocks the shaft a very tiny bit to the side, it also rubs a little. I belive these two ever so slight interferences conspired to make the pump shaft hard to turn.

I will let you know if that fixes the problem and if the shaft is turning freely, but at this point, it is looking that it may be something minor that took a little figuring out.

best regards,

mike

[Gossioii6]

Looks like your question thing at the end of the post worked. Also not having to sign in is nice too. Good job. Nice list. Thanks.

[Tokyo Torquer]

Just to follow up.. issue resolved.. no major problem, just took a little finessing in 3 places and now the shaft turns freely. Each time I massaged one of the points, it got progressively easier to turn. The 3 points that I touched up were..

1. a very small ridge right where the machined step is inside the distributer hole was addressed with a few strokes of a flat file.
2. the rear main cap nut was touched up with a dremel tool so that it was flush with the washer with the flat side (when I turned the block right side up on the and when the pump shaft fell down onto the pump, it just barely hit the shoulder of the nut and cocked the shaft a very tiny bit to the side, it also rubbed ever so slightly)
3. Even though the shaft seemed to have plently of room in the hole that goes through the rear main cap, when I bolted the pump down, it caused the shaft to catch the parting line between the cap and block.. again ever so slightly. I used Carl Hinkson's recommendation to machine down the Melling IS55E drive shaft.. putting the shaft in a 1/2" drill and using a belt sander with 120 grit .. machined the shaft just below the collar (at pump end) down to .425". Worked like a charm.. thanks for the idea, Carl!

All in all, turned out to be nothing major. Just so tight in there with the 400 mains and with the thick bulkhead.

thanks for your help!

mike