how to shim oil pump
Well, I just went through this. I put a number of posts up asking about it, but only got 1 or 2 responses and they were educated guesses. I did a h/c in Oct and changed to a Katech ported pump. I found out afterwards that Katech doesn't shim the pump. I had 35 psi at idle to around 70 psi at 6500 rpms before. After I put it all back together I had lost 5lbs. across the board. So I had 29-30 psi at hot idle (oil temp 195+) and 65psi at 6500 rpm's. I just did a cam redegree and pulled the heads to have them milled some more. When I had the front cover off to change the timing gears I pulled the oil pump and shimmed it. I removed the bypass seal and put a washer in that was just shy of .060" thick. When I put it all back together I had 33psi hot and 70psi at 6500rpms. If I were to interpolate from my experience I should have put in about .100" of shim to get back my 5psi. But I do feel better about my pressure now.
TECH Resident
Joined: Aug 2004
Posts: 875
Likes: 2
From: Portland Oregon
From GM there is no shim under the bypass spring. I read that TSP adds a .110 shim, that should be good for about a 10-15 PSI increase. I recently added a .145 to my race motor, that brought it up from 45 to 60. I just turned a small piece of aluminum on the lathe. It's about .41 in diameter, it fits inside the allen head threaded plug on the bypass spring.
So all that I do is lets say that the pump is on the motor, On the right side there is a little allen head bult I take that out and put a washer in that spot and then put the allen head bolt back in. I just made another post about what is going on with my oil pump if you guys can look at that. I really apreciate the help I wish I would have know this back in Februrary.....
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removed spring "cap", install ~0.100", +/- 0.020" washer/washers (two 0.060" = one 0.120") in "cap" (so they need to me small enough diameter to fit IN the "cap"), and put the "cap" back on.........
pump bypass spring is now shimmed
pump bypass spring is now shimmed
