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 smaller oil filter
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wakesupremo
Cochise

United Kingdom
653 Posts

Posted - 18 Mar 2017 :  12:33:19 PM  Show Profile  Reply with Quote
I have fitted a smaller oil filter and have noticed a significant decrease in oil pressure at lower revs. Is this a coincidence or can a small filter starve oil from the top end of the block where my gauge is situated. The filter I have fitted is a Wix 51042.

Steve C.
Crazy Horse

1568 Posts

Posted - 18 Mar 2017 :  1:37:06 PM  Show Profile  Visit Steve C.'s Homepage  Reply with Quote
Not sure if it relates but your 51042 filter is rated 9-11 gpm flow which is the same as the common 'regular' size WIX 51258 filter.
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Steve C.
Crazy Horse

1568 Posts

Posted - 18 Mar 2017 :  2:40:33 PM  Show Profile  Visit Steve C.'s Homepage  Reply with Quote
Also both of those filters have the same 21 micron rating. When you buy a filter that catches smaller particles, the filter media is more restrictive and has increased pressure drop across the filter.
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Phil
The Great White Buffalo

USA
7129 Posts

Posted - 18 Mar 2017 :  10:36:15 PM  Show Profile  Reply with Quote
Is the bypass blocked off?

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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wakesupremo
Cochise

United Kingdom
653 Posts

Posted - 19 Mar 2017 :  03:39:35 AM  Show Profile  Reply with Quote
Which bypass do you mean Phil? All Ive done is taken the old filter off and replaced with the smaller one to get the bottom of the filter away from the header tubes.
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Phil
The Great White Buffalo

USA
7129 Posts

Posted - 19 Mar 2017 :  09:01:57 AM  Show Profile  Reply with Quote
The filter bypass in the housing. Some block it off (bad idea in my opinion) to force all oil through the filter.

How much difference are you seeing in pressure?

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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wakesupremo
Cochise

United Kingdom
653 Posts

Posted - 20 Mar 2017 :  09:09:54 AM  Show Profile  Reply with Quote
The actual diameter of the filter gasket is the same so I expect the bypass is still clear. The motor idles still at 45 psi as it has always done but goes down to 20 when revved then creeps back up slowly while the motors still revving. Its when I pull away from a junction or similar. Sits at 45 psi at the junction with gear in neutral as the revs are applied tp pull away it dips down to 20 psi then creeps back up to 60 slowly. It always sat at 45 psi at idle but rose immediately to 60 when revs applied before.
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Phil
The Great White Buffalo

USA
7129 Posts

Posted - 20 Mar 2017 :  10:05:30 AM  Show Profile  Reply with Quote
I wonder if your pickup fell out of the oil pump.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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wakesupremo
Cochise

United Kingdom
653 Posts

Posted - 21 Mar 2017 :  08:45:21 AM  Show Profile  Reply with Quote
Ill have another run out at the weekend and see if I can work any sort of pattern out. Thanks for the replies.
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GtoGuy32
Cochise

USA
824 Posts

Posted - 21 Mar 2017 :  7:29:36 PM  Show Profile  Reply with Quote
1. Pull that oil filter, cut it open and check for bearing material.
2. Change the oil if its the same oil before putting it away for the winter (assuming you dont drive year round)
3. Put a regular sized Wix filter on there (or NAPA Gold)
4. Re-run,

If oil pressure is still low, then.....

Pull the pan and check things over.

Don't leave oiling issues up to coincidence or chance. Something is up.

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RayK
Cochise

USA
921 Posts

Posted - 21 Mar 2017 :  9:06:25 PM  Show Profile  Reply with Quote
I've tried smaller filters and have had similar results. I wouldn't ever use a smaller filter.

1969 Firebird 461, #62 iron heads, Comp roller, Performer RPM, Q-Jet Turbo 400 w/ Continental converter. GM 8.5" 10 bolt with 3:73 gears.11.60's@ 116+ MPH
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loosetappet
Buffalo

87 Posts

Posted - 21 Mar 2017 :  10:00:30 PM  Show Profile  Reply with Quote
I have tried both large and small in my 400 and haven't seen much difference.
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Steve C.
Crazy Horse

1568 Posts

Posted - 22 Mar 2017 :  10:30:52 AM  Show Profile  Visit Steve C.'s Homepage  Reply with Quote
A fwiw, I have seen Cliff Ruggles post he has used the NAPA 1042 filter. Same filter as the WIX 51042 in question here.
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RayK
Cochise

USA
921 Posts

Posted - 22 Mar 2017 :  9:09:51 PM  Show Profile  Reply with Quote
If thats the smaller filter, he took it off a long time ago for the same reason. Oil pressure dropped.

1969 Firebird 461, #62 iron heads, Comp roller, Performer RPM, Q-Jet Turbo 400 w/ Continental converter. GM 8.5" 10 bolt with 3:73 gears.11.60's@ 116+ MPH
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Steve C.
Crazy Horse

1568 Posts

Posted - 25 Mar 2017 :  09:48:15 AM  Show Profile  Visit Steve C.'s Homepage  Reply with Quote
Cliff experienced lower oil pressure with the smaller 1042 filter. His guess was that the small filter just doesn't have enough flow capacity for the oil pump. He is using the oil pump bypass and presumed it must go wide open anytime the oil is cold, and probably dumps more oil when it is hot.

But again, many others have used smaller filters with no apparent issues.

Edited by - Steve C. on 25 Mar 2017 09:48:47 AM
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