Should the oil pump sit flat against block - 340?

[Playtimefun]

I just got my Meiling HV pump for my 340 rebuild and when I check the fit, it sits about a 1/16" above the #5 cap.

I am assuming that the oil pump should sit flat. So do I need to take a grinder to the block or the neck of the pump to make it fit?

Secondly, how many threads should the oil pickup fit into the pump? The new Milodon oil pickup only wants to go in about 2.5 threads in which sure doesn't seem like very much.

 

[Playtimefun]

Ok. Oil pickup goes deeper. Just have to keep working it an eighth of a turn then back.

But the oil pump itself is definitely hitting (not the main bolts) the inside of the hole. I did read for some Chevy models to put the oil pump in the freezer for 2 hours to cool it but that's for when it's a tight fit versus this is a "I ain't going in fit"

 

[DetMatt1]

Hopefully a small block guy will come along and chime in on this because I have been all big block for decades but never ever take a grinder to any machined surface!!

 

[Racer Dave]

It just so happens that I have a new Melling pump on the shelf and a 340 short block being assembled. The pump didn't want to start right away so I measured the pump neck and the main cap bore. Both are exactly .6875" which is a light press fit. I did take a piece of emery cloth and make sure there was no burr at the top of the pump neck. A couple taps with a dead-blow hammer and it went in the full depth - although tighter than any I've ever assembled. Before final assembly I'll probably take a fine grit paper and polish the pump neck - only a few ten thousandths (.0001") should be enough for an easier fit.

I'm not using the stock pickup tube but rather a bottom pickup for a deep oil pan that replaces the bottom cover, so I'll be plugging the inlet port. It's a standard 3/8 NPT tapered pipe thread and you could tap the hole slightly deeper if needed; but if you do it will be mandatory to disassemble the pump and clean out any metal chips from tapping. If you can get at least three threads as-is should be enough, so that may not be necessary. It needs to be tight because it's both a fluid seal and it holds the pickup in position slightly above the pan floor.

 

[Racer Dave]

While you're in there.... this is a good mod to the oil passage to complement that HV pump. BEFORE assembly of course

 

[moparleo]

Just an FYI, the service manual says that the oil pump pickup should rest on the bottom of the oil pan.