What size tap for OIL PIPE PLUG

[Miasma]

Hey everyone,

This block is a 4g64 from a 2003 outlander. I'm building this engine with a dohc evo 8 cylinder head, and need to block off five of the main oil galleries. I have already blocked off three of them but have two left to do.

The picture below is of the two holes I still need to plug...

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When I measure the inner diameter of these holes with my calipers they measure 0.71". When I went to the local parts store they did not have any pipe plugs that would fit that size. The bronze plug was a 1/4inch and the two silver ones were 1/2inch. The parts guy told me the next size of pipe plug is 0.81", to use this plug I would have to drill and tap these holes.

Do you guys know if this is right, or if there is a pipe plug size that will fit the 0.71" hole tapped.

 

[BogusSVO]

You may want to try a 3/4 X 10 bolt

Make the plug yourself from a bolt or a chunk of all thread.

Cut a slot in the top and use a large flat head screwdriver to install.

Make sure you have the block decked, you are distorting the HG surface with the tapping and plugs.

 

[Miasma]

Thanks Bogus, was wondering if I would get a response from you on this.

I was planning to have my block resurfaced after this, it has a bit of surface rust too but nothing major. The local store has 3/4 pipe plugs but when he measured them calipers they measured .81 so I guess I might just have to drill them out a bit with a 20mm bit.

 

[19Eclipse90]

A 3/4-10 bolt is not a 3/4 NPT pipe plug. A 3/4-10 bolt needs a 21/32 hole which is 0.65625" for the tap, i.e., no drilling necessary, only tapping. (Using this as a reference, BTW: http://www.boltdepot.com/fastener-information/us-tap-drill-size.aspx)

Dale -- any reason you didn't suggest a 3/4-16? Seems like a better option since it uses a 11/16 (0.6875") hole and its a finer thread which seems like it would give it more meat in the block to hold on.

 

[donniekak]

I believe those holes do not need blocked when using an evo 4-9 cylinder head.

 

[SlowSpyder]

I believe those holes do not need blocked when using an evo 4-9 cylinder head.

I agree! Those holes only need to be blocked off when using the older twin cam evo 1-3/dsm head on a 4g64. The evo 4-9 heads have the same oil drain holes. Reason I say that is I used a cosmetic head gasket for the evo 4-9 on my sohc 4g64 build.

 

[Miasma]

Thanks for the responses guys.

I didn't know I could leave these holes open, thanks for pointing that out to me. I will wait until I get my HG and align it to see for certain if they need to be blocked or not.

Thanks for the link Brian.

 

[BogusSVO]

A 3/4-10 bolt is not a 3/4 NPT pipe plug. A 3/4-10 bolt needs a 21/32 hole which is 0.65625" for the tap, i.e., no drilling necessary, only tapping. (Using this as a reference, BTW: Bolt Depot - US Tap and Drill Bit Size Table)

Dale -- any reason you didn't suggest a 3/4-16? Seems like a better option since it uses a 11/16 (0.6875") hole and its a finer thread which seems like it would give it more meat in the block to hold on.

I am not a big fan of fine threads in cast iron, the thicker corse threads , to me seem to cut better in the cast. Since it is a drain and not a stress point , either would work.