Breather and PCV valve setup

[Nobby]

I've fitted a PCV into one valve cover on my 383 linked into the Air Cleaner and an ordinary breather in the other valve cover. Whilst running the engine earlier today I noticed that oil was running out of the breather - not a lot but still enough to form a pool on the ground.

Would it be a better idea to run the PCV into the negative pressure port on the carb base plate to improve suction? Or run 2 PCVs both into that port?

Thanks

[MarkT]

If you are going down the PCV route, you need to run the PCV pipe into the negative breather port at the carb base plate.

You need another hose from the other valve cover to the air filter base plate.

This will allow air into the crankcase at low revs when there is negative pressure, maintained by the PCV and as crankcase pressure builds up with the revs and the PCV shuts, the pressure is released into the air filter body and passes through the combustion process.

Hope this helps.

Markt

[Nobby]

Cheers Mark, I'll set it up that way and see what happens.

Nick

[Purple AK]

Originally Posted by MarkT

If you are going down the PCV route, you need to run the PCV pipe into the negative breather port at the carb base plate.

You need another hose from the other valve cover to the air filter base plate.

This will allow air into the crankcase at low revs when there is negative pressure, maintained by the PCV and as crankcase pressure builds up with the revs and the PCV shuts, the pressure is released into the air filter body and passes through the combustion process.

Hope this helps.

Markt

I ran mine in that configuration in the beginning and it created too much vacuum/smoke/sucked the oil out of the rocker covers. Now changed to PCV plumbed into the carb full vac port.And the other Rocker Cover breather open to Air. Works for me :thumb:

[wilf]

Chris - I read both posts twice, and I am missing something. If you are both plumbing your PCVs into the full vac port on the carb base/inlet manifold, what is the difference in the set up between yours and MarkT's, that stops "too much" vacuum being available?

I can't see that your other breather being to free air, and his being in the air filter should make any difference (no additional vacuum inside the air cleaner?)

[Miket]

Originally Posted by wilf leek

Chris - I read both posts twice, and I am missing something. If you are both plumbing your PCVs into the full vac port on the carb base/inlet manifold, what is the difference in the set up between yours and MarkT's, that stops "too much" vacuum being available?

I can't see that your other breather being to free air, and his being in the air filter should make any difference (no additional vacuum inside the air cleaner?)

None, unless he made the same mistake as I did (which has since been rectified) and also used a PCV valve from the valve cover to the air filter, I still have a PCV fitted, but have taken out all the working bits so it is now free flowing.

[MarkT]

Exacty, thw wholw point being that the pcv causes a small vaccuum in the crankcase, the free flowing air from the pipe to the air filter allowing to replace that drawn by the PCV.
The only reason to have an open pipe to the air filter and not just a vent to atmosphere is to take away any smell and oil mist which could contaminate your engine bay.

The other option is to dispense with PCV and instead vent both valve covers to atmosphere via a catch can. This allows any oil mist to seperate and has to be emptied as it fills up.

Brgds

MarkT

[Purple AK]

Originally Posted by wilf leek

Chris - I read both posts twice, and I am missing something. If you are both plumbing your PCVs into the full vac port on the carb base/inlet manifold, what is the difference in the set up between yours and MarkT's, that stops "too much" vacuum being available?

I can't see that your other breather being to free air, and his being in the air filter should make any difference (no additional vacuum inside the air cleaner?)

Sorry Wilf/Guys. Maybe I didn't make it as clear as I should have
The PCV was/is plumbed to full vac (inlet manifold in my case) The other rocker cover breather was "open" plumbed (no PCV) to the base of the air filter. In this configuration it used to smoke when coming off of tickover. Changing to an open to air breather on that side stopped it smoking. I suspect this was because the rocker cover on that side is unbaffled, and oil mist was being sucked into the air cleaner.
Make more sense?

[wilf]

Umm. I think so - the lack of baffling in one of your rocker covers probably explains it. I assume the other one was baffled? Or at least, slightly confused?