Newbie help low warm oil pressure 360

lockedup

This motor has about 20,000 on it. Runs great, no oil usage. Cold pressure at start up 80..Warm up runs about 35 at 60 mph. Warm idle at about 12..( this is what scares me) We run around town alot and have low pressure. What can an inexperienced motor guy do to try to bring up the pressure? I have read about the spring/plunger , but not sure where to start. I am using Napa gold filters. I have done intakes, water pumps , but not an experienced mechanic. I think the mid plate might help too. Can some one point me in the right direction to try these. I need some specifics. Thanks

mike4089

honestly its no better then mine...actually its better i have about 10 at idle...my motor doesnt make any weird noises and runs awesome...i gave up on trying to find the problem and will run it till it stops turning

lockedup

Thanks Mike..I am going to put some mobile i in her and run it..I had 2 304s years ago and they did the same.. I just thought if there was an easy fix I would try..

jeepsr4ever

Sound slike the bearings are in good shape but you have excessive pump clearances. You really dont have to live with 10psi at an idle if you have good bearings.

lockedup

jeepr4ever, Can you give me some instruction to fix. Not that up on motor work, but not afraid to try. Thanks

jeepsr4ever

Probly the best thing you could do right now is install a new oil pump gear kit and a midplate. The midplate will take care of the gouges in the bottom of the pump and the gears will give you tihter pump clearances. Its not that bad of a install usually takes a novice about 1/2 hr. You will have 7 1/4-20 bolts holding the oil filter adaptor in. You will need a extension and a deep socket to get at a couple of them and then the oil filter adaptor will pop off. The oil pump gears will slide out and you just make sure the old gasket is off the bottom of the pump and the top of the oil filter adaptor. Then you install the new gears and the midplate with a gasket on both sides of the midplate and bolt it up (No RTV or gasket sealer needed). Then you should have more oil pressure. If you dont get a nice increase you may have a worn timing cover

fifesjeep

jeepsr4ever wrote
Probly the best thing you could do right now is install a new oil pump gear kit and a midplate. The midplate will take care of the gouges in the bottom of the pump and the gears will give you tighter pump clearances. Its not that bad of a install usually takes a novice about 1/2 hr.

:-| Sounds like you're trying to sell some goods, the real question is, Are they really needed :idea: :mrgreen: lol, just teasing man... I couldn't resist :oops:

In My Opinion... First check the base plate, if there is any gouges in it, depending on the depth of the gouges you can lap the plate to a smooth true surface. If the gouges are deep you can bring it to a machine shop and they can mill it for a few bucks... or you can go to a junk yard and possibly pull one for a couple bucks... If the plate appears to be good look at the inner walls where the gears reside... IMO this is the critical area. If there are gouges on the inner walls then you're basically SOL... and that is probably the oiling issue, (providing that the rest of your oiling system is up to par, mainly the bearing tolerances etc). My experiences have shown that if there is gouges in the base plate the inner walls are gouged also... Like Jeepsr4ever said, you want tight tolerances/clearances for better oiling pressure...

Jeepsr4ever: You mentioned new gears for tighter tolerances... Is the O.D. of the gears "slightly" larger or what? Did you change the number of teeth? I know about the little "design" at the base of the teeth.. But, Curiosity is killing me... wait, or is that from the cheap beer that I had last night??? :-|
Anyway, on all of my "old" oiling gears the O.D. never changed and the "tooth wear" was so minimal that you could barely see it on gear tooth vernier... and that was probably an error on my part... one of my old 304's had 89,000+ miles on it and the pump was original with no signs of wear, (surprisingly)... The Mains were tired so I changed them and had the crank brushed up and at a warm idle the 304 had 15-17psi depending on the oil filter/oil used. (Then I ran her at 7000+ rpms a few times and chewed the mains)... My 401 runs about 14-17psi at warm idle... w/10w40... my lopey 360 sits around 18psi at warm idle and that's with 20w50 race oil... and a few oiling mods :?

jeepsr4ever

The ends of the gear teeth tend to wear with the pump wall so you can see a few psi difference with new gears. Fife is right you can go the cheap route and try to refinish your oil filter adaptor. A piece of glass with sandpaper on top of it will get out the gouges but it can be a little painstaking.

fifesjeep

jeepsr4ever wrote
The ends of the gear teeth tend to wear with the pump wall so you can see a few psi difference with new gears.

Honestly, I never really noticed the ends... :-| I'll have to look now. I was thinking about a new design for the gears (basically the bottom with a slight radius etc) The radius would be so little that with the naked eye it would be hard to see it unless you had a true surface next to it... I'm not sure how this would work with PSI though...

Fife is right you can go the cheap route and try to refinish your oil filter adaptor. A piece of glass with sandpaper on top of it will get out the gouges but it can be a little painstaking.

Being in the Military and having two hungry boys... I have to pinch pennies all while trying to turn a penny into a dime... Not always the easiest route but it saves me the "wtf bla bla bla" from the old lady" :roll: (sometimes)... And depending on those gouges chances are you'll be there for a minute trying to clean it up... lol
You know you're cheap when the local Junk Yard knows you by a first name basis... :oops:
I can't remember if it was on this forum or not, but wasn't there another set of gears from a donor vehicle... the OD was slightly larger and had more teeth... so a little machining is required... arethese from a pontiac/olds??? Anybody heard of this?

lockedup

Wow I really appreaciate the response. One more question do you have any pics or diagrams so I can get a feel of what I am going to be doing. I think I can handle this, just like to see before I jump in. Thanks again

JD

A good place to start is the AMC Technical Service Manual. Heres a few pages from a 1973 TSM thats online and should get you familar with things and give some ideas of what to do.Go to pages 1B-15 and 1B-16 and it will tell you about rebuilding the pump.

http://www.tocmp.com/manuals/AMC/1973/Service/Part1/1b/browser.htm

The specs for the pump are on page 1B-23

lockedup

Thanks JD!!!

lockedup

One more stupid question..After replacing gears and installing midplate it will need to be primed too..Might be getting in over my head..read some posts that after changing had lower pressure..I would love to do this, just worried I will make it worse. Thanks again!!

fifesjeep

You should definitely pack the pump, use vasoline... and pack it solid... you can then fire it up OR you can remove the distributor and use a priming tool...

jeepsr4ever

You really dont want to use and vaseline. You shoudl use the same weight oil you are going to run in your engine and just lightly coat the gears will be more than plenty. Years ago Melling (which supplies all AMC oil pumps) had a little sheet of paper that said pack the pump with petrolium jelly. They now say soak the gears in clear oil. The reason being that petrolium jelly will clog you oil filter until it reaches 100 degrees and activate your oil filter bypass. The old vaseline prime works but can cause instant bearing damage.

fifesjeep

No $h!t.??? I didn't know that... I must be lucky :!:... So far I haven't had any issues... but then again... after I pack the oil pump I normally prime the motor with my electric drill... The bypass will open when the pressure reaches what... 60-70psi??? depending on the spring pressure... sound about right?