Oil pump end clearance gear resistance problem?

I also had problems when trying to measure the amount the gears protrude out of the pocket using a feeler gauge and straight edge. I had the same issue of the gears binding so I assembled it with various gasket combinations until I could feel a LIGHT drag when turninig the shaft.

At that point you are at 0 clearance. Then just add .002 - .003 to the above combination of gaskets. Assemble it dry and double check that it turns freely and you can feel the end play before you pack it with vasiline.

 

I'm thinking twice . . that was fun dropping by the tent occasionally to watch the action.

I like polishing the ends of the oil pump drive and idle gears with 1200 grit emery cloth, as I find new ones in particular are not that smooth on the ends. I also like to add a steel wear plate at the end, for a consistent wear surface. The last one I put together still turned with the thinnest of the shims from the kit, and no gasket so that is how it was assembled. It seeps a little, but otherwise creates great oil pressure. The folks in Michigan I got the shim kit and wear plate shall remain unnamed on this board.

 

I used the dial indicator and with a .01" thickness on gasket and shim stacking I was able to dial in between 0 - .002" shaft end play on the gear. So there is uneven wear in the gear pocket. Does anyone have any suggestions on this? If I leave the shims at where they are now, will the steel gears eat away at the aluminum gear pocket until it eventually evens out to .002" all around. Or should I move up an extra .001" in shim height to make a .001" - .003" clearance and hope the steel gears eat away at the aluminum gear pocket also?

 

Increase the clearances and see how it performs. Under no circumstances do you want to do anything to promote wear of the pocket by the gears.

Devon

 

I recommend not doing the ****ty feeler gauge with a straight edge technique. The readings I got from the feeler gauge were way off from what I got with this dial indicator.

First you are going to start off with the stock gasket, torque the oil pump cover back onto the timing cover to spec and check to see if your oil pump drive gear spins freely. If it does not spin freely, then you need to add shims to heighten the gap till you feel no resistance. Once it spins freely, and is able to move up and down (in and out) just by a tad bit, then there is some sort of end clearance. The way you will measure this end clearance is by doing this:

With the timing front cover off - Have a dial indicator that has a long enough shaft to meet the shaft of the oil pump gear through the hole where the distributor would sit. This dial indicator's shaft will have to be around 4" in length.



Place the dial indicator snug to the surface of where the distributor would sit. Place the tip of the dial indicators shaft to the tip of the shaft of the oil pump gear.



Grab the shaft of the oil pump gear and move it up and down (in and out) while holding the dial indicator in place as best as possible. However much the shaft of the oil pump gear moves in and out will be your end clearance.



Make sure you rotate the gear shaft 1/8 turns and recheck the in and out movements on each turn. Timing cover gear pockets can be worn unevenly over the years (such as mine), and it's best to check full rotation of the gear before completing final assembly. If the indicator read .001" all the way around, then you need to add a .001" or .002" shim to your setup. If the indicator reads .004" then you need to remove .001" - .002" of gasket thickness. I've read that you generally want between .002" - .003", but .002" is your best bet for sure fire oil pressure throughout RPM ranges. As long as all other clearances within cam and main bearings are adequate of course.

 

Hi there,
I find all of this very interesting as my hot oil pressure on my engine is around 5 psi at 500 rpm in drive foot on brake. I didn't do this shim thing, perhaps that's a contributing factor. But how much difference can it make? Will I see an additional 5 psi at idle? Has anyone had really crappy idle oil pressure and then seen a huge improvement with a smaller shim or gasket? (Note my Higher RPM oil pressure is great).

Thanks for the input.

Best Regards,

Clint

 

Clint, an engine with larger bearing clearances (or other internal leakage), but a healthy oil pump will behave exactly as you describe. It's still wise to dial in the pump clearances to help at pressures lower than where the relief valve is set.

Devon

 

The bearing clearances are at about .0025. Think that's the issue? I wish they were .002 but alas it's to late for that now. So do you think the 5 psi is a big deal? I will try the the shims but if that doesn't fix it should I worry? At rpms I have great pressure. Also is TA performance the only ones with the shim kit or can I get something from Napa.

Thanks,

Clint

 

Clint, pretty much any pressure at idle will do just fine as long as it rises with rpm as you're already seeing. The pressure is really needed when cylinder pressure rises as the throttle is opened, not such a big deal at idle under such little load.

I will say I've not heard of any small block guys complaining about this, usually it's the big blocks that suffer low idle pressure with bigger clearances.

Devon

 

Thanks Devon. I will let you know what it does when shimmed. Its never low enough to light the low pressure light, the sender for which is tee'd of of the line for the oil pressure gauge. I was debating the dreaded high volume pump, but now I think I will correctly shim it and see what it reads esp. with real oil not break in. Could make a difference.

Thanks again.

Clint

 

Clint, at 5 psi, the light should be lit. Does the oil light illuminate at key on? If I remember right, the stock warning light should illuminate at or near 7 psi, I may be wrong.

Devon

 

Let us know what the oil pressure is at 2500 RPM and also at 4000 RPM. There is no issue with using the high volume oil pump on the 350, lots of people do this with no issue. It is the 455 that does not like the high volume pump.

 

Just as a point of clarity for me...

The "booster plate" is really just a steel plate that brings the oil pump cover back to a perfectly flat surface again, right? It's only purpose is to repair a damaged oil pump face?
My oil pump cover/filter holder has some scoring on the face of it, and I would sure rather pay $25 for a plate than $60 for a whole new cover, unless there is a clear reason to get rid of the old worn one.

Opinions?

 

The booster should increase oil pressure throughout the Rpm range, protect the cover and strengthen it.

---------- Post added at 09:51 AM ---------- Previous post was at 09:41 AM ----------

Hi Devon, yes the light does work.

 

If you replaced your cover with an aftermarket check side gear clearance as well. I will be putting my old cover back on as the tolerances were all within spec. My replacement cover will not even serve as a good boat anchor. :grin:

 

Gear pumps are very common and can easily produce thousands of psi. What is different about this one is that it uses an aluminum housing, and the ends of the pump cavity often are not quite square with the shaft and pin (bearings). Normally you would expect the gear end faces to be perfectly perpendicular to the shaft as well, as it should be based on the manufacturing process. If only it was that simple. We see from the varying end play (0.000"-0.002") that this is not the case. If the gear ends were true, the only possible variation in clearance would show up between adjacent teeth. For instance if the face the filter housing bolts to were cut at a slight angle. Having the clearance vary as a function of rotation means that the gear is taller on one side than it is on the other, but it also means that the bore is taller on one side that the other. The result is that as the gear turns it gets tight, and then loose. It is also possible that the gear has burrs on the ends, or has been dinged. Typically the ones I've seen are rather coarsely machined on the ends and have not been deburred. So a good first step is to take some fine cut jeweler's files and LIGHTLY knock off the sharp edges, just enough to ensure that nothing projects past the end of the gear. The flat file can be used to go over the end to take out any high spots. We're only talking about a thousandth or so here so stay away from the 6 or 8 inch mill bastard file unless you really know how to use it. The housing itself can be off either in the end of the pocket, or much more likely, at the mating flange. It would not be a surprise to see 0.001-0.002" of variation across that face but to measure it you need a dial indicator mounted on a shaft or an old gear. Unfortunately accurately re-cutting this flange is going to be very difficult, and re-cutting the end of the pocket, nearly impossible.

With the right tools you can blueprint the pump gears and cavity and correct them down to half a thou of cold running clearance but for most this won't be possible. Luckily there are a few tricks you can try. Some Prussian Blue dye is going to be very helpful, it's an intensely pigmented paste that comes in a tube. A little bit goes a very long way. If you dab a small smear on one tooth and then put the gear in the housing and turn it, you can tell by transfer where the end of the cavity is high or low. (or not) Likewise, transfer from the housing to the gear will tell you if the gear end is square to the bearing. You can do the same thing with the cover end. Once you know what you are working with, it is possible to dress down the high spots on the gears by hand using the jewelers files, and it is even possible, using a larger clean, sharp, fine cut flat file to dress the housing flange the same way. But again, we're talking about a very small amount of metal that needs to be removed. Also obviously both the drive and driven gear need to be exactly the same height.

Once this is done it is possible to set the end clearance accurately. If everything is square and true this can be done by shimming until the gears just lightly drag, lubricating, and spinning the gears with a drill until they seat in and turn smoothly, at which point end play should be less than 0.001" It will increase as the housing warms up.

As far as the clearance on the diameter, this isn't overly critical, the cavity does not wear in this area and there isn't much to be done about it if clearance is too great except to replace the front cover. But the oil is pulled all the way around the gear from inlet to outlet so leakage here means going against the grain almost all the way around the gear in opposition to rotation so it really takes a pretty large gap to drop the output pressure.

Jim

 

Jim,

One of the best pump write-ups I've read.

Devon