Oil Pump Rebuild - AMC 304

Wanted to brake this out of my rebuild thread.

Started to do the rebuild on the oil pump this week, in preparation for the engine coming back from the machinist next week. So, ordered a rebuild kit from my local parts store - NAPA. And a set of additional gaskets from Bulltear. Rebuild kit is from Sealed Power part #224-51285 NAPA #601120

In preparation I had a good read at another forum on a nice rebuild how to.
http://www.jeepforum.com/forum/f8/amc-v-8-oil-pump-front-cover-rebuild-thread-1050446/

I started by lapping/sanding the oil filter floor plate. The engine has about 64,000 miles, and a lot of abuse - think spun bearings. Lots of scoring on the plate, but a good hour of work and all looks smooth and flat.

Before oil filter floor plate


After oil filter floor plate


Also did a little lapping / sanding on the housing to make sure it was smooth and flat. Sorry no photo.

Now for the issues. When I install the new impellers, It is very hard to rotate them. Almost impossible at times, as they seem to drag a lot on the housing. The impellers on the rebuild kit measure out a little wider than the old parts.
Original Impellers
Main shaft driven = 1.488 to 1.490
Driven impeller = 1.490
New Impellers
Main shaft driven = 1.494
Driven impeller = 1.494

The original impellers have a lot of scoring on the outer edges, and I suspect this may have a lot to do with the measurements. And I also suspect that the old impellers have worn with the housing.

Internal Housing





Any recommendations?

Do I use the new impellers, and spin them up with a drill to "wear" in the housing?
Do I use the old impellers?
Do I ind another housing?

Thoughts?

 

If you use a drill to wear in the housing you're going to get metal particles all through everything plus end up causing damage. I'd find serviceable parts.


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What's the clearance between the housing and your original gears? That's the important quantity, in addition to the end play of the gears with the filter housing and gasket in place.

I presume you are replacing your cam bearings.

The conservative approach here is to find another timing cover, either a good used one or a new replacement (Crown). Using a new housing does not excuse you from measuring the side and end clearances as you put the housing together though. The TSM shows how to measure the gears-to-housing side clearance.

I am surprised that the new gears are an interference fit into your housing. The housing cannot get tighter as it wears ... the only way I see that the new gears interfere with the housing is for the new gears to be out of spec.

My personal opinion is that replacing the gears is usually not required and inconsequential. It's the soft aluminum housing that wears, not the gears, as witnessed by the scoring of the housing.

Bulltear would likely give you a spec for the gear diameters. They sell these parts too. Definitely do not install the gears if they are an interference fit to the housing.

 

Endplay I could get into specification, it's not far off. But between gear and housing it's not good. I could not get me smallest feeler gage between the gear and the housing, on the leading wall of the non driven gear - 0.0002. If you look closely at the photos above you can just about make out what the problem is - extra bits of metal embedded into the aluminum housing.

Looks like I need to change the title of this thread to "How to buy a timing case cover / oil pump" :evil: