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| Oil pump pressure relief plunger https://slantsix.org/forum/viewtopic.php?t=68734 |
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| Author: | ceej [ Sat Aug 22, 2026 9:59 am ] |
| Post subject: | Oil pump pressure relief plunger |
Howdy! Were there different length plungers used in slant oil pumps? We have a 60's pump and a F-body pump. Big drop in oil pressure with hot oil at idle. Down to nothing on a mechanical gauge. It's possible the plungers got swapped betwen the pumps. Were there different plungers used between the 5 bolt and 6 bolt pumps? "Asking for a friend."  I don't know squat about F-body era stuff. CJ |
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| Author: | SlantSixDan [ Sat Aug 22, 2026 1:10 pm ] |
| Post subject: | Re: Oil pump pressure relief plunger |
As far as I know, all the same. Are we sure the plunger isn't partly or fully stuck? |
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| Author: | ceej [ Sat Aug 22, 2026 3:38 pm ] |
| Post subject: | Re: Oil pump pressure relief plunger |
Yessir. The plunger has been out and cleaned up. It's been torn down with a new spring and such. I'm beginning to suspect the square o'ring seal on the cover might be the culprit. Some of the aftermarket ones are apparently made slightly thicker than stock, which can result in excess side clearance on the pump. We're going to triple check for flatness while it's apart. Seemed OK, but one never knows till you put it to float glass and check. It just takes an extra thousandth. CJ |
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| Author: | SlantSixDan [ Sat Aug 22, 2026 5:11 pm ] |
| Post subject: | Re: Oil pump pressure relief plunger |
Interesting. Keep us all posted on what you find, yeh? |
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| Author: | volaredon [ Sun Aug 23, 2026 6:30 am ] |
| Post subject: | Re: Oil pump pressure relief plunger |
I thought all original pumps were 6 bolt, only (some) aftermarket ones were 5 bolt? |
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| Author: | slantzilla [ Mon Aug 24, 2026 10:38 pm ] |
| Post subject: | Re: Oil pump pressure relief plunger |
IIRC, if the cover has 2 "bumps" on it like my 76 motor did, you have to be careful to orient the cover in the proper place or you end up with no pressure at idle. Go ahead, ask me how I know this.
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| Author: | SlantSixDan [ Tue Aug 25, 2026 11:35 am ] |
| Post subject: | Re: Oil pump pressure relief plunger |
Yup, the kidneys need to be between the bottom two cover bolts, as installed. |
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