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Thread: Holden oil pump

  1. #1
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    Default Holden oil pump

    Can someone tell me what size welch plugs in need for the holden 304 oil pump
    The small one thats standard and what size to block off the relief valve
    Thanks benno

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    You need to measure the hole where the bypass comes out, there are differences. The other worthwhile mod is to leave the little welch plug out and tap down and set a short grub screw just below the pressure relief. Then the relief gets its signal from in the filter not the engine. It will save you destroying oil filters like I did.

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    Sure why not? 76lxhatch's Avatar
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    I wouldn't be blocking the relief valve completely, that will cause you problems

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    Not the relief, it's the bypass you delete.

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    Quote Originally Posted by RedTaxi View Post
    You need to measure the hole where the bypass comes out, there are differences. The other worthwhile mod is to leave the little welch plug out and tap down and set a short grub screw just below the pressure relief. Then the relief gets its signal from in the filter not the engine. It will save you destroying oil filters like I did.
    Ok what size tap and grub screw do u use?

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    Sure why not? 76lxhatch's Avatar
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    Quote Originally Posted by RedTaxi View Post
    Not the relief, it's the bypass you delete.
    Still what I was referring to, I guess both the pressure and bypass valves could be called relief. When the filter is blocked or can't handle the pressure (common when cold especially if using heavy oil), oil goes around so your engine doesn't starve. Block it and under any of these conditions you lose oil pressure.

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    Senior Member 46Crab's Avatar
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    The bypass valve (if filter gets blocked) requires a 19-21mm welsh plug, some old pumps apparently take a 3/4 plug. There are some variances in pumps, so measure and check your pump, they are not all the same. You can use a 1/2NPT hex plug for the bypass valve as well.

    The small welsh plug can be removed and plugged further down the hole by using a 1/4NPT plug to change where the relief valve references from.
    Im currently doing a pump at the moment based off TK suggested mods and a few others minor changes. Ill attach some photos Im using as a reference to give you an idea of what Im talking about. Note: there are not my photos, Ive found them in the inter web as a guide.

    Lastly, Im no Jedi on this shit but confident in what Im doing for my application. There are plenty of threads from well know Holden V8 Jedi, like TK and Zok on these pumps. [IMG]https://uploads.tapatalk-cdn.com/20200930/3f6163bf104f4c2a45c1702322535e8c.png[/IMG]
    [IMG]https://uploads.tapatalk-cdn.com/20200930/a249d050310bb937395b7e1a16cdfa70.plist[/IMG]
    [IMG]https://uploads.tapatalk-cdn.com/20200930/3ec3c3ec9b6a30ddbca60aee338bea0b.plist[/IMG]

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    Yep 1/4NPT and get a 1/4NPT plug and shorten it to about 1/4". Tap down till the plug goes tight just past the pressure relief piston. Not too far or you will start to block the main engine feed. Best on a factory alum pump. The JP iron pumps have some slight differences and one that I tapped the threads broke into the relief piston seat. Or you could drill down a fraction bigger and leave a little seat and tap in a plug and loctite in place.

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    Quote Originally Posted by 76lxhatch View Post
    Still what I was referring to, I guess both the pressure and bypass valves could be called relief. When the filter is blocked or can't handle the pressure (common when cold especially if using heavy oil), oil goes around so your engine doesn't starve. Block it and under any of these conditions you lose oil pressure.
    Yeh a blocked filter will cause trouble. I've never had a blocked filter though. Till I did the above 2nd mod I was collapsing filters which shows how much pressure it was getting when cold. Also that oil completely bypasses the filter when cold, which I dont really like. Now oil has to go through the filter at all times. If there is too much pressure the relief valve now takes care of it.

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    ...

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    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by 46Crab View Post
    The bypass valve (if filter gets blocked) requires a 19-21mm welsh plug, some old pumps apparently take a 3/4” plug. There are some variances in pumps, so measure and check your pump, they are not all the same. You can use a 1/2”NPT hex plug for the bypass valve as well.

    The small welsh plug can be removed and plugged further down the hole by using a 1/4NPT plug to change where the relief valve references from.
    I’m currently doing a pump at the moment based off TK suggested mods and a few others minor changes. I’ll attach some photos I’m using as a reference to give you an idea of what I’m talking about. Note: there are not my photos, I’ve found them in the inter web as a guide.

    Lastly, I’m no Jedi on this shit but confident in what I’m doing for my application. There are plenty of threads from well know Holden V8 Jedi, like TK and Zok on these pumps. [IMG]https://uploads.tapatalk-cdn.com/20200930/3f6163bf104f4c2a45c1702322535e8c.png[/IMG]
    [IMG]https://uploads.tapatalk-cdn.com/20200930/a249d050310bb937395b7e1a16cdfa70.plist[/IMG]
    [IMG]https://uploads.tapatalk-cdn.com/20200930/3ec3c3ec9b6a30ddbca60aee338bea0b.plist[/IMG]

    and don't forget TK's oil pump thread is a sticky here...

    https://www.aussiev8.com.au/showthre...erformance-use
    __________________________________
    ONE OF THE Aussie V8 MODERATOR/ADMIN TEAM

    Never late in an AussieV8!
    Club circuit racing...the best fun you can have with your pants on

  12. #12
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by 46Crab View Post
    The bypass valve (if filter gets blocked) requires a 19-21mm welsh plug, some old pumps apparently take a 3/4 plug. There are some variances in pumps, so measure and check your pump, they are not all the same. You can use a 1/2NPT hex plug for the bypass valve as well.

    The small welsh plug can be removed and plugged further down the hole by using a 1/4NPT plug to change where the relief valve references from.
    Im currently doing a pump at the moment based off TK suggested mods and a few others minor changes. Ill attach some photos Im using as a reference to give you an idea of what Im talking about. Note: there are not my photos, Ive found them in the inter web as a guide.

    Lastly, Im no Jedi on this shit but confident in what Im doing for my application. There are plenty of threads from well know Holden V8 Jedi, like TK and Zok on these pumps. [IMG]https://uploads.tapatalk-cdn.com/20200930/3f6163bf104f4c2a45c1702322535e8c.png[/IMG]
    [IMG]https://uploads.tapatalk-cdn.com/20200930/a249d050310bb937395b7e1a16cdfa70.plist[/IMG]
    [IMG]https://uploads.tapatalk-cdn.com/20200930/3ec3c3ec9b6a30ddbca60aee338bea0b.plist[/IMG]

    and don't forget TK's oil pump thread is a sticky here...

    https://www.aussiev8.com.au/showthre...erformance-use
    __________________________________
    ONE OF THE Aussie V8 MODERATOR/ADMIN TEAM

    Never late in an AussieV8!
    Club circuit racing...the best fun you can have with your pants on

  13. #13
    Do you ever leave? EH179's Avatar
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    Hey Smitty, I heard you the first time!

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    So by tapping this and using the grub screw does this move the relief valve out so it cant go in as much?
    Im trying to get my head around this lol
    And if u dod this do u still put the .100 shim to make spring tighter?

  15. #15
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    So by tapping this and using the grub screw does this move the relief valve out so it cant go in as much?
    Im trying to get my head around this lol
    And if u dod this do u still put the .100 shim to make spring tighter?

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