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Rebuilding The Oil Pump In An AMC 360ci V8

Posted in How To: Engine on August 12, 2015
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We have owned our 1979 Jeep Cherokee (SJ) for a few months now, and although it's a bit rough, we have fallen in love. The body has a few dents and dings and carries that rust/old paint patina that we will likely never ruin with a spray job. All the mechanicals are in running order, although as any Jeeper knows, nothing is ever perfect, especially when you're dealing with a steel and rubber critter that was born in the age of classic rock 'n' roll. We had noticed almost since the day we brought her home, though, that the oil pressure is not always up into what we would call a confortable range.

We knew it was time to deal with this oil pressure drop. There can be a few culprits causing it, but after a thorough examination, we determined that the most likely was the oil pump. Our first clue was the seeping from the mating surface between the oil filter adapter (a neck-like cast aluminum feature between the pump and filter) and the bottom of the oil pump housing that is integrated into the timing chain cover. This was merely an indication of the problem inside.

The oil pump housing and the oil filter adapter are both aluminum. However, the gears inside the oil pump hosing are steel. The bottom sides of the steel gears rotate against the top of the aluminum filter adapter. Eventually this creates a swirl pattern carved into the filter adapter. This gap (or tolerance) created underneath the bottoms of the steel gears and the aluminum surface they ride on can allow oil to bypass the gears and lower overall oil pressure. The gear teeth can also begin to wear and lose tolerance, which doesn't help keep up proper oil pressure.

There are several fixes: repair or replace the gouged up filter adapter; replace what may be worn-down oil pump gears; or use a steel midplate between the oil filter adapter and the oil pump housing to prevent the gears from cutting into the aluminum filter adapter again. Some don't like using a midplate because it means there are now two gaskets (one on each side of the steel midplate) through which leaks might occur, instead of the single gasket between the filter adapter and the oil pump housing.

However, the solution for us was the Bulltear Oil Filter Relocation Kit (PN 626). It meant we could do away with the scarred oil filter adapter completely and have a remote oil filter. The Bulltear kit includes an oil filter relocation end plate for the oil pump housing bottom. The end plate is a beautifully machined billet aluminum piece that retains the oil pressure bypass spring and plunger, and features two 1/2-14 NPT ports capable of flowing a -12 AN line. The kit also provides brass NPT fittings (two 90 degree and two straight), two 15-inch lengths of Parker 5/16-inch hose (PN 5139-10 WP) that is rated at 310 psi, and a remote oil filter adapter (PermaCool PN 1791). We wanted to mount the remote filter up in the engine compartment on the inner fender wheel, so we needed more than 15 inches of hose. Fortunately, we found all we wanted through the Parker Hose website, which directed us to its nearest distributor.

We also replaced the oil pump gears with a new set from BJs Off-Road and decided to go with the steel midplate as well. Even if you repair or replace the aluminum adapter, the steel gears are going to continue to eat at any aluminum part they ride on, and you are just going to have a pressure problem there again. The steel midplate and its gaskets came from Bulltear.

The entire job took about half a day, and it was fairly easy as go this sort of mechanical work and modifications. The end result is that we now have more oil in the system because the remote system adds oil capacity in the length of its hoses, the filter is up and out of the way so it's much easier to change oil and filters, and our oil pressure returned to a much more comfortable range. This was something that we were very happy to see.


01 This seeping oil filter adapter gasket was a problem we needed to fix. It led us to dealing with a low oil pressure problem we had wanted to take care of since we had acquired the 360ci V8-powered '79 Jeep Cherokee.

02 One of most important things you can do to help solve a low oil pressure problem on the AMC 360ci V8 is to rebuild the oil pump. A set of new gears, and oil pressure bypass spring and plunger from BJs Off-Road was a good start.

03 We also wanted to put a remote oil filter setup into the 360's oiling system, and the oil filter relocation kit from Bulltear helped us accomplish that goal. It also provided an opportunity to ditch the factory oil filter adapter. The Bulltear kit included a machined billet aluminum filter relocation end plate, NPT fittings, hoses, and a remote oil filter adapter. We needed more hose than the Bulltear kit came with and easily found it at a local Parker Hose distributor. We also got a midplate kit (it comes with two gaskets) from Bulltear.

04 There is little room to spare between all the steering gear, transmission cooler tubes running to the radiator, and the oil filter adapter. However, with some patience we removed all seven of the bolts that attached it to the oil pump housing.

05 Be careful when removing the oil filter adapter, as there will be a substantial amount of oil left in the pump even though you have already drained the system through the oil pan. As well, one or both of the oil pump gears may fall out as the adapter is removed. If the drive gear (right in this photo) doesn't drop out on its own, it can be easily pulled out. The top of its shaft is splined to mate with the bottom of the distributor shaft.

06 All of the new oil-pump internals, such as the bypass spring and plunger and both pump gears, were coated with generous amounts of petroleum jelly (Vaseline) for lubrication during the priming of the oiling system before firing up the engine. We also packed the oil pump housing with petroleum jelly to completely surround the gears. This will also hold the gears in place until you can install the filter relocation end plate. When your buddies ask why you have a container of Vaseline in your toolbox, just tell them it's personal.

07 We used yellow (for gas lines) thread sealant tape when installing the NPT fittings into the Bulltear machined billet aluminum oil filter relocation end plate for insurance against leaks. The bypass plunger, spring, and bypass bolt and washer were installed at the same time.

08 Using the factory bolts we had cleaned up after removal, and with a dab of anti-seize on them to keep these steel bolts from permanently joining with the aluminum oil pump housing they were going into, we installed the Bulltear remote oil filter relocation end plate and the midplate with its two gaskets. Gasket sealer was used on both gaskets. We hate leaks.

09 After installing its NPT fittings, we held the remote filter adapter bracket in place on the inner fender where we wanted it and used a center pump through its mounting holes to mark our drill points. Next, we drilled three 3/8-inch holes for the 5/16x1-1/2-inch threaded bolts we procured at our local hardware store and used lock washers (on both sides) and nuts to secure the bracket to the inner fender.

10 The final touches on the installation were to run the hoses between the input and output NPT fittings on the remote filter relocation end plate and the remote filter adapter, secure the hoses with clamps, and then install the new oil filter. We disconnected power to the distributor so the cylinders would get no spark and cranked the engine using the starter to prime the oiling system. Our 360ci V-8 now has oil pressure we feel good about, running around 60 psi when cruising and about 40 psi at idle once the engine is warmed up.

Sources

Bulltear Industries
Lindstrom, MN 55045
651-257-7917
bulltear
Bj's Off-Road
253-320-7604
http://www.bjsoffroad.com

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