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09 ZD30 CRD Wagon
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Discussion Starter #1
I have a leaky rocker cover gasket, and on the CRD that unfortunately means a whole new rocker cover assembly.

before I install it, I was wondering about enlarging the crankcase breather hole so I could run a straight piece of 25mm hose from crankcase to the provent catch can, and do away with the reducers I have now.

has anyone done this? I assume it would mean drilling out the hole and tapping it to a certain size that would allow a 25mm barb to screw in. Question is, what type of tap must be used??
 

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Typically you want a BSP tap. Size will depend on the size on the end of your barb as they can come in a few sizes stepped down or up. Obviously if you want a 25mm hose tail you don't really want to step down much if at all. So a 1 inch BSP tread would suit. I/d will still be smaller but going to a bigger thread size will make it harder to find a tap and if the cover is not that thick you don't have many threads to engage. there are other threads and sealing options but they are not as common.

You could get someone to weld an ally tail on to the cover after you drill it out which maximises your internal bore.

I have no idea if this is important on a CRD but it can't hurt. Is it worth the effort though??
 

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Jack, there was a discussion about exactly this last week on a Facebook page Boosted ZD. Caleb from G Turbo has done this by drilling out and tapping a thread into the rocker cover.

523668
 

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nissan patrol
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If the material is too thin to support tapping the threads you could use a bung on the underside of the cover if there is clearance and just tighten them together.

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Jack, there was a discussion about exactly this last week on a Facebook page Boosted ZD. Caleb from G Turbo has done this by drilling out and tapping a thread into the rocker cover.

View attachment 523668
Thats neat in theory but I looked at AN fittings for the TD but problem is suitable hose size and the I/d ends up too small and barely an improvement if you are chasing a much bigger bore.
 

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Thats neat in theory but I looked at AN fittings for the TD but problem is suitable hose size and the I/d ends up too small and barely an improvement if you are chasing a much bigger bore.
Yes agreed, but I was more pointing out that the fitting can be drilled out and tapped into the plastic rocker cover.
 

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1989 GQ TD42 wagon
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Just what sort of pressures are we talking about? I know when I had the EndlessAir installed the bloke I had do the installation said, "No real pressure involved [intake side of the pump], so I can bore out most of the wall thickness and it will get better airflow." The fitting was rated to 20 bar (~300 psi).

Could be an option here, too.
 

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Just what sort of pressures are we talking about? I know when I had the EndlessAir installed the bloke I had do the installation said, "No real pressure involved [intake side of the pump], so I can bore out most of the wall thickness and it will get better airflow." The fitting was rated to 20 bar (~300 psi).

Could be an option here, too.
Rocker cover or crank case pressure should be pretty low like under 5 psi. That is the blow off pressure on the Provent catch can.
 
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