I've been reading up about the oil pump priming problems people have on this forum and I don't want any of these problems to happen once I'm finished with my build. I have a new stock melling oil pump kit, ta booster plate, ta shim kit, and ta oil pressure regulator. The timing cover has been cleaned up by my machine shop along with the oil pump cover. So I can't tell if there was much wear in the oil pump pocket of the front timing cover. I've checked the end clearance for the oil pump on my buick 300 with a straight edge and feeler gauge and am getting a close .002" - .0025" clearance. I've also used plastigage and have been getting the same clearances around .002". This clearance is snug and my build-up manual states a .0023" minimum. According to what I've read, if I add the stock .005" gasket from the shim kit, I should have the preferred clearance of .0025" - .003". Once I install the oil pump assembly onto the timing cover with booster plate and gaskets, torqued to 8ft lb, I am not able to move the gear shaft by hand. If I use a screw driver to rotate the shaft clockwise, I am able to spin it a little, but there is much resistance felt and heard by the grinding of the gears. I doubt there should be any resistance on rotation of the gears. But I don't want to keep stacking shims until the gears stop grinding and have a clearance well over .003". Should there be resistance felt on the oil pump gears once fully torqued? Am I not calculating the clearance correctly causing me to need a thicker shim? Is the timing cover gear pocket worn too deep? I've also tried the stock gasket from the melling oil pump kit, tried not using the booster plate, tried not using the regulator spring, and tried a .001" shim on top of the .005" gasket - but I continue to get the same results. Any comments, questions, or answers will be greatly appreciated.
Isn't .002 clearance and a .005 shim = .007"? Did you completely pack the cavity with vaseline and prime the oiling system until oil presuure built up/
There shouldn't be any grinding at all. The .0023 minimum is the amount the gear faces sit above the gasket surface. If it is less than that, or even with the gasket surface, the pocket is worn. If the timing cover is off the engine, you should be able to use a dial indicator to measure the end clearance with the pump assembled.
No, if the dimension is being reported properly, the 0.002" is how much the gear is protruding from the pocket. Thus 0.005" - 0.002" = 0.003" actual gear end clearance when it's bolted together. Devon
A quick update: I am able to use the .005" gasket plus the .003" shim on the assembly which causes no grinding of the gears. But this makes my clearance at .006", which is double the recommended. I have also tried using my old oil pump gears but I get the same end clearances. The engine has been machined and cleaned. It's sitting on an assembly stand and I have recently finished the bottom end build up. Once I install the front timing cover, I'll be able to move onto the head work - but I'm stuck on this oil pump issue.
That is correct. With a straight edge ruller and a feeler gauge, I am getting .002" - .0025" fluctuating end clearances. Why would a .005" gasket causing a .0025" - .003" actual end clearance, cause resistance when trying to spin the gears? Is there something I am missing?
You aren't measuring end clearance with the straight edge and feeler gauges. You are measuring how far the gears protrude ABOVE the gasket surface. The gasket creates the end clearance. My only conclusion is that you are not measuring accurately enough. That is why I suggested using a dial indicator to measure the ACTUAL end clearance. You can set a dial indicator up on the end of the pump drive shaft, with the timing cover in a vice. move the shaft up and down and watch the dial indicator. That will be your actual end clearance. If it binds, you have NO end clearance, or maybe the pocket is worn unevenly.
From the factory, what did they do? I assume they assembled the oil pump with a single gasket and that was it. I do not understand why shim gaskets need to be used along with a stock thickness gasket, when assembling these pumps Yes, I understand we need to set the end clearance properly, but why does it vary from pump to pump? A worn pocket would have you using a gasket SMALLER than stock gasket, not a stock gasket + shim..... makes no sense to me, unless these replacement gears are being produced with wildly inconsistent dimensions. And Poiz, what do you mean by "cleaned up" - did the machine shop do something to the oil pump/timing gear covers? That might not be good...
The reason it varies even with new parts is due to production machining tolerances and the dimensional stack up between the timing cover and the gears. If engineering determined that worst case stack up in either direction (a) couldn't result in a bound pump and (b) provided adequate oil pressure and volume even at max end clearance, then one gasket thickness would have done the job. If they determined that more control was needed, they may have had multiple gasket thicknesses available based on data obtained from a test fixture for the assembly of each cover. It would be neat to know what they ended up doing. The need for an aftermarket shim kit is obvious; gear pocket wear can be accommodated to some degree, and it enables dialing in the max efficiency of the pump itself for high performance use. Devon
Right or wrong.. I tighten it up with the shim kit till I can't turn it and slowly back it off with the shims until it is a semi tight turn.. Measuring never worked for me.. No expert by far.. What did the factory do?? Screw it together?? Then they did the 20 minute can break in?? Sorry, it sarchastic Friday..
So if there is gear pocket wear then the stock gasket is useless as it is too thick.. Is it OK to use the shims by themselves with no gasket??
I used the .010 shim gasket for about 4 months, all by itself- no leaks at all. In other vehicles, like a Lotus engine I used to have, the plastic shim is the only gasket used to seal the housing...so I don't think there is any problem using just the shim. But I am curious about this as well- because the kit is specific about using the gasket with a shim- but I have no idea why. I did set-up my own pump with plastigage and the shim kit- it made a big difference in pump pressure. I also had the same problem that poiz had- at .002, the gears would not turn by hand. Makes me wonder if some of the cases of broken oil pump drive shafts is due to this problem. If I had just thrown on the stock gasket without measuring, it probably would have snapped something when I started it back up.
Grand mas Electra never saw the high side of 4500 RPM. We are turning them 1000 RPM higher. The whole point of blueprinting the pump clearances is to get the most out of it. With the small block, it isn't that big of a deal, but on the BBB, if you don't have enough oil pressure for the RPM you are turning, goodbye engine. Just ask Adam Martin (Smartin)
Why would it snap? Unless you somehow had ground the surface down more than stock? I'm having a hard time picturing this causing binding if there is too much clearance. Unless it allows the gears to cock sideways and bind? I've been reading the maintenance manual on how to do this correctly, and am wondering if just getting a new housing and have it set up before I tear into the nose of this thing would be the smart approach? AAARGHHH, what a hokey design....
I'm not an engineer, but it seems if the oil pump is even close to specs it would provide more than enough oil if the engine bearings were close to specs.. How bad was Adam's oil pressure???
So I should install the gasket and shims that do not make the gears bind, torque the oil pump cover to spec, put the timing cover onto a vice, and measure the pump's drive shaft that is protruding from the inside of the timing cover with the dial indicator? If it moves up and down within .002" then everything is good to go? If it does not move within that range then add the correct shim thickness until I got between .002" - .003". Am I understanding this correctly?
Take some pictures of this process and post them please? I've never done this and would like to make sure I'm set-up before I tear it apart. Thanks
