I am resealing my old leaky chrysler 318 (1975). it was running in my charger 2 months ago when I parked it and put it up on jack stands to install the felpro gasket set. I did the valve covers, then took the front of the engine apart and took off the oil pan. I installed a new rear main seal, then new oil pump and reused the pickup tube. I positioned the oil pickup in the same position it was in before. Then I put a new pan gasket on the oil pan and put it back on the bottom of the engine. Then I replaced the timing chain and sprockets with a comp cams magnum double roller chain and sprocket set. I put a new front main seal in the timing cover and a new cover gasket, then put it back on the engine. I Installed the mechanical fuel pump back into the side of the timing cover. Then the water pump. I put the damper back on with an installer tool, then bolted the crank pulley onto the damper. Finally, I put the harmonic damper bolt back on and torqued to 135 ft/lbs. As I did this the the crank rotated but then stopped and wouldnt budge. I torqued it down then tried to turn the crank with a normal ratchet.. wouldnt budge. So, I tried turning it the other way (counter clockwise) and it turned just fine until I turned it a full 360 degrees and it stopped again, in the same place it hit before. I've now turned the crank back and forth 360 degrees each time and the crank just keeps jamming up in the same spot.

I dont know whats happening. My best guess is that I may have positioned the oil pickup tube just a little wonky and one of the crank counterweights is hitting it, so I can turn the crank just until it hits then reverse and the same thing happens. Or maybe my fuel pump arm was installed wrong? The damper doesnt look like its binding up on the timing cover, and I didnt remove the camshaft retainer plate when I had the timing chain off, so I dont know what the problem is. I hope its not the oil pickup tube... I spent a lot of time cleaning and prepping the pan and block surface for the new gaskets and rtv sealent and I dont want to have to take the pan off and mess up my work.

Any suggestions
?

This is how we lean from our mistakes. I think the best way is pull the pan and have someone rotate the crank and see what you are hitting.

Crank counterweight hitting the oil pump. If so just grind a little off of the pump case so it'll clear

Did you reuse the same crank pulley to balancer bolts?
I had a friend install longer than stock bolts on the lower crank pulley and they went through the balancer and hit the timing cover.

It's still a 318 as the 340 has same stroke as 318. Good you found problem though.

Same stroke/rod length between the two. iirc 340 cranks are forged so either someone wanted a forged crank instead of a cast one in that bad boy or that was what they happened to have on hand when they put her together. I'm assuming that black spot where you've ground away clearance is a hot spot from grinding & not a hole going all the way thru

Sometime in 72 340's got cast cranks, 73 340's were cast crank, so it could be a cast crank .

First of all, you can tell it's a casting because you can see the screw heads where they screwed the casting number onto the mold. It isn't necessarily a 340 crank, I'd say the odds are at least 90:1 against it. If it was a 340 crank, the #1 and #4 rod throws would have lightening holes drilled in their ends.

Do a better casting number search and you'll find that 3751841 is a casting from which either 340 cast cranks or 318 cranks were machined from probably late 72 all the way through the 2000s.
http://www.ebay.com/itm/U508-CRANKSHAFT-3751841-2000-DODGE-RAM-2500-OHV-/151034540158
BTW, absolutely nothing wrong with a 318 cast crank. They're good for 500+ horsepower IMHO.

R

I bought a melling m72 oil pump, that's what all the stores said was the stock replacement pump. So, since it doesn't fit right, what oil pump/part number do I need for a standard 1974 318?

You actually have the right pump & a stackup of tolerances just happened to happen in this case. do some light/shallow grinding there on the case where the witness mark is where it's hitting. grind judiciously then trial fit then grind again till it just clears. .035" (spark plug gap) or a slight bit more should be plenty. PATIENCE (grind lightly/fit/grind lightly/fit)

Ok, thats no problem. I've read a lot of bad things about melling pumps and the relief valve sticking. How do I check that? I dont know if the reports were from mopar specific applications though.

"I've read a lot of bad things about melling pumps"

Welcome to the Internet age. You can read a lot of bad things about anything. The problem is, if you buy an oil pump, there's a 98% chance it is Melling. Does anyone else even make oil pumps anymore?

R.

I cant believe you didn't burn the bearings out of this motor with that hole in the pump! everything I know about a car I learned by screwing it up at least once, and even ive never done that!