Amc 360 Low Oil Pressure On Idle

Hi guy's i know this subject has been covered some time before but i want to have a clear answer on what i'm planning to do.

My amc 360 has been professionnaly rebuilt 6 years ago. Oil pump has been rebuilt with new Gear but i doubt that the end plate wasn't rebuilt to.

When cold start i have a strong 45-50 psi but when cold it goes as down as 5-10 psi at idle. There is no clicking noise when at that low psi but i would like to get more so i will stop stress when wheeling the jeep. When i hit the throttle the pressure jump but will never go above 30 psi when hot.

I'be reading for a while on different forum (here too) and a good fix seem to be a mildplate. I was looking for the oil recolation kit from bulltear. I already have a oil relocation kit but it goes over the oem filter as opposed to bulltear that seem to be better since it bolted directly over the oil pump gear.

This sollution seem to give some more oil pressure at idle but i would also suspect the front cover, the gear housing could be worn out causing the pressure to drop. From there bulltear offer a new front cover with nickel plated for durability. But for around 400$ i want to make sure it will solve my low oil pressure.

From there, I like to know what others as done to get better pressure at idle.

I need to swap out the 2 row pulley for the 3 row pulley so it's time to work on the oil pump since i'm taking off the front shell to do the job.

 

It seems the three main reasons for low hot idle oil pressure in these engines is 1) mains and rods worn out (like any other engine), 2) poor clearances in the oil pump (from wear possibly resulting from too few oil changes), and 3) delaminating camshaft bearings (not as common as the oil pump, but fairly common).

I suggest you skip the mid plate and instead follow Ristow's oil pump rebuild tutorial given here - V8 timing cover/Oil pump refresher. pic heavy. - International Full Size Jeep Association - the mid plate does not correct for the proper gear clearance. It only corrects any gouges in the oil filter adapter. You need to lap the timing cover so that the gears sit proud of the gasket surface by the proper amount. The end clearance of the gears is the most important measurement, though the side clearance of the gears can be measured too. You can use feeler gauges or Plastigage for this measurement. This is also described in the manual very well.

 

In my case i would doubt number 2 reason. As stated engine has been rebuilt from top to the pan, engine run strong and i realy doubt that number 1 and 3 will be the problems.

If it's the side clearance the problem do i absolutly need a new front cover?

 

I don't think there is any way to fix the side clearance other than replacing the cover. However, the word is that the end clearance is the main source of hot idle low pressure. Also, there's plenty of agreement that you are better off with an old, refurbished cover than a new cover. If I had a cover that was broken or had corrosion holes, I would look for a good used replacement before I bought an aftermarket cover. Worth the extra effort, IMO.

 

Thank's Tim, you are right on the point as always. I will go as you comment and the tread you provide me before going with the big buck replacement part.

 

FWIW I have the oil filter relocation kit from bulltear nice part took a long time to get and I still lapped the gear side to make it flat. I port matched the holes in the block and timing cover and increased the size in the oil port at the 90 in the block.

 

Tim is spot-on with his comments. One additional comment; what weight oil are you running? A heavier weight oil may help bring pressure up a couple pounds at idle.
Back to Tim's comments, the oil pump needs to be "blue printed" making sure the clearances are absolutely perfect. As the engine warms up, all the clearances get slightly larger due to expansion, as well as the oil thinning out. Like Tim stated, the oil pump gears need to protrude slightly past the surface of the timing cover, with the gasket making the clearance. Old gasket sets used to include 3 or more different thickness oil pump gaskets to accurately set the end clearance. This proceedure is best done on the bench before the timing cover is fit to the engine. If there is too much end clearance, the pump in not efficient at low rpms, an oil pressure may be low at idle.
-Donny

 

Yes Donny, i'm going to work it off on the bench.

I need to swap out the harmonic balancer for the 4 bolt version (i have the 3 bolt) so i could use the 3 row pulley. I will do it at the same time since i want to do a complete sealing of the engine so i won't have any small leak.

I can order a gasket for the oil pump with napa but i cannot find a complete set of different thickness seal for it, so i can make sure the set-up is perfect.

Also i need to know what grit of compound to use for the lapping....

 

As for compound i just call napa guy, i will have the valve grinding compound that the guy use in the tread that Tim linked to me.

 

500 grit wet sandpaper with oil worked slick.

 

Yes, I've seen this done with wet-or-dry paper taped to a piece of plate glass.

 

i will get a small glass at our local shop and use the same product as the guy used on the link you provide me. Napa as the valve grinding compound so i order it there this morning, should have it tomorow.

 

I use a hunk o granite counter top a little oil Under the paper a little oil on the paper it all works good

 

Tim you are still right...again...

Have bought a new cover...a proform one. Oil pump and distributor line up perfectly when not on the engine. Make a lot ao measure with a micrometer. But when cover is on the engine i cannot have the distributor to fully seat. Always have a 1/4" to get fully seated. I've try to rotate the crank to get it in....but the most i get is 1/4" and the distributor feel very tight and i cannot turn the body of it...

so i will start the lapping process on my old one and hope that the scratches in the cavity wont be a hude deal on the pressure.

 

When dropping the distributor in, you have to align two items in order for the distributor to seat as it should be. First, you are aligning the gear that drives the distrubutor with the camshaft. You need to anticipate the partial turn the distributor rotor must turn as the gears mesh.
You must also line up the oil pump drive shaft at the same time. You can stick a screwdriver down the hole, twisting to orient the drive shaft with the tang on the bottom of the distributor. Like I mentioned above, you have to anticipate the twist of the rotor as the gears mesh together so everything aligns to allow the assembly to drop into place.
All this while, I asume you have set #1 cylinder to top dead center and the rotor pointing to #1 position on the distributor?
-Donny

 

Yes i have try that for 3 hours yesterday, doing 1/32 of a turn each time. Even try to turn the crank by hand so it could drop right in without any result.

I really think from this point that it come from the taiwan cover. Tonight i will try my old cover so i will see it the distributor seat in.

Also i have another gasket for the cover, i will give a try with two gasket, maybe i can save the day with that.

 

Just put the old one back in(cover) distributor fall in at the first try.


Bad cover

 

You could try a new cover from BullTear. The word is they take the import covers and test them for proper machining. No experience - just what I've heard.

 

seems as of late bulltear is not really around?

 

I have not heard any official word that they are gone - but their customer service has always been lacking. I expect it's a one-man hobby business and success and/or life has interfered. I would search for recent posts about business with them before sending them my money.