If you've been living under a rock, you probably haven't heard that there have been lots of issues with new oil pumps for your 134 cu in 4cyl. Willys engine. I myself had this issue with the pump locking up and snapping teeth off stuff. Fortunately, mine only broke the oil pump teeth. Some have had the cam teeth break off.

The best way to tell which pump you have is simply look at the cover. The new ones have the pressure release built into the cap. The old style has the pressure release built into the housing.



The internals are totally different too.



One thing I noticed while taking these pictures is the old style pump has an oil galley on the housing so oil can get to the shaft. The new one does not. I wonder if this is the problem with the new ones? You can see the missing teeth on the left side of the gear on the new one.




So here's the scoop, if your original oil pump works fine and your engine had good oil pressure, reuse the original pump. My engine rebuild kit came with the stuff to rebuild the original pump, gaskets and the relief spring.

Mine was properly installed. I had primed it properly and when the engine was running for the first 5 min, it had great pressure, 40 psi, then it shut off because the distributor quit spinning. Mine was a Melling. When I rebuilt the V6 in the Jalopy, I used a Melling pump. I know they make good pumps, but for some reason these just don't work. The drive shaft in my pump is what locked up. The idler gear falls right out into your hand. As you can see in the pictures too, there if very little wear on the cover. So I have no idea why this happened.

If your new pump has been working fine, I wouldn't worry about it. Most people have had them lock up in the first few minutes of the very first startup.

Gentlemen, I've been a mechanic and eng builder for 60 yrs. Melling WAS always a good pump. Few people had trouble w/ them. I always rebiuld and blueprint the original pump on every eng I do. Many antique rare engs have no parts available so I make my own. Ocassionally a pump will be broken so I find another used one to rebuild. My understanding from my warehouses is Melling has been having the pumps made in China for the last few yrs. A lot of failures. I always dismantle and verify a new pump when supplied. The seizures and problems w/ the Mellings is w/ pumps for all brand engs, not just these 134s. I suggest the rebuild route. David

F Bill, All clearances are poor fits. Rough surfaces. Many burrs on housing and gears. Just no quality control at all. Another real problem I've found is the built in pressure relief valve will "hang " open partially or fully and they'll be low or no pressure. this problem can be erratic. I'm seeing this on Flathead Fords and hear many complaints on the subject. That's why I rebuild the originals. Never have a problem. Parts of the Stephentown 3B will live on. David

Gunslinger, That's one of the problems w/ people "rebuilding" their pumps. The gasket does not set the "head space" as you called it. (a new term to me). It is the responsibility of the installer to know these things. You can't blindly think the gasket is correct. It usually isn't. The "body to gear" end clearance must be verified accurately taking into account that gasket. Either trim the gears, the body or eliminate the gasket to obtain no more than .002". Orig gskts are typycally .002-.003". Most kit ones are much thicker creating low pickup suction and low pressure. Everybody is worried about lash between gears. It is NOWHERE as important as gear end play. David

Thanks for getting the aluminum pump on here too Randy.