Wait, What! 225 oil pump clearance question.

My service manual for the 225 buick says the clearance between the pump cover and gears should be between, .0023 and .0058. Is that right or did they put the decimal in the wrong place? I'm not a precision machinist by by any means, but that seems almost negligible to me.

 

My guess is the decimal is in the right place. Think about a loose .002 ranging up to a little over .005, not quite .006, sounds right to me.

Don

 

That is measured without the gasket on the timing cover right?

 

No...that should be the clearance with the gasket in place

 

.0023 is two thousands plus 3 tenths of a thousand..........for the most part having measuring equipment that measure in tenths of thousands are not common in the average shop.
One other thing while you have that oil pump off a common upgrade is to use the longer V8 gears inside your pump........there are kits from places like TA Performance and Milling that have new gears, a spacer, shims and assorted relief springs .........adds increased volume to your oil system.

 

Does seem like a lot though. But I only have the AMC to compare with. AMC calls for 0.5 to 2.5 thousandths, with 0.5 preferred. This is less than the gasket thickness, so the gears sit proud of the housing.

 

Just make sure you actually have clearance when it is all bolted together or it will lock up. I can't see using gears that stick out of the end of the pump by any amount, that seems way too tight to me*. Just how thick is the end plate gasket on that pump?

Seems like a lot of guys have been getting oil pump lockups and cam gear breakage on the 4 cylinders lately , and I have a feeling this clearance issue is what has been getting them...so on your V6 if you don't know for sure what is is supposed to be and how to measure it, check with someone like a good machine shop to ask their opinion. It isn't something you want to have wrong, and it seems like a lot of pumps are shipped with the wrong gaskets or people are tightening them way too tight or ??? Too much clearance will drop your oil pressure, too little you lose the motor in a worst case scenario.

*Ignore this statement. See the below post with a FSM illustration that proves me wrong.

 

From my site http://www.vortexbuicks-etc.com/Oilpump.htm check the caption on figure 23 toward the bottom. Pictures are from the manual, comments are mine

The above is from the 231 manual. Most of us try to get closer to 0.002 than 0.006" for best oil pressure tho' I doubt that oil pressure is that critical on our 225's due to the lower rpms and the lesser loads. TA Performance sells packets of gaskets of varying thicknesses so one can dial in a minimum clearance, but, on these engines, I would not worry as long as it falls within the spec.

 

I'm a 4 cylinder guy, so I guess I will just keep quiet. There is obviously something different going on here than what I am used to.

 

As long as you are reading 10psi of oil per 1,000 rpm, you are good to go.

 

Got it set to approximately .003, I took it into work and used their feeler gauge to get it. I had to polish some off the gears and use a slightly thicker gasket.