Hi!

With original intake with PCV valve is easy conect the breather hoses of engine
Let me know how i will conect twin Mikunis and a Harada intake mainfold, i cant put the PCV valve on breather system
Where i will link the hose rocker cover and engine breather hose?

Anybody who has twin carbs on engine please give me your advices.

Luigi

Rocker Cover: fit a small air filter

Block breather: connect to PCV valve

PCV valve: connect to small canister, about 250cc. Connect four small vacuum hoses, one from each intake runner, to the canister. This way the intake pulses are smoothed by the canister.

Since the crankcase is no longer directly connected the the carburetor backfire is no concern

Alternatively, if you have an air cleaner, it is better to connect Rocker breather hose to the inside of the air filter. In this case use the stock anti-backfire hose.

You can drill & tap a port in each runner




Or just use a catch can as racers do. This is a racing manifold with no provision for the factory systems. The engine will run OK but you will smell the crankcase fumes.

Peeps should consider the round port head for EFI with that manifold by DD above as there is a member with 100kws atw with efi and boost yet has no special cam yet.

For what most are after on the street round port head with efi and boost is overlooked

I bought these http://www.ebay.com.au/itm/BRAKE-BLEE ... -PACK-OF-10-/200730472846 and ran a drill down them to get rid of the seat. I then tapped a hole for one in each runner. Then I connected each one to a vacuum tree and plumbed the PCV valve and plumbing into that. Works a treat and was pretty easy to do.

Hi!

If you please can send me some pics of your system breather, i thinhk you make perfect job and i would like to make it equal.
My intake mainfold has plug for booster. (i can install the vacum booster too?)

My intake mainfold is the picture enclosed

Many thanks

Luis

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Luckily I took a photo sometime before for someone else. It's a bit cluttered but hopefully you can see what's going on.

Edit: I didn't take a photo of the bleed screws I modified but hopefully you get the idea.

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  Engbay 2.jpg (150.12 KB)

Hi!

Many thanks for your reply.
My intake mainfold has one hole for a vacuum hose booster and one mark to make another hole.
If i drill the mark, can i introduce a brake bleeder on mainfold and insert a PCV valve and link to block breather. Or put a T on intake mainfold, one for vacum booster and another for PVC valve?
In rocker valve put a filter.
I dont like the ideia to connect both breathers to an oil-vapor separator.
What do you think?

Luis

I am thinking like you - I don't like oil vapor separators. Better to keep the crankcase clean.

The brake booster has a check valve and a Plenum of sorts (vacuum chamber) so it can build up vacuum from a pulsing source. So it is OK to connect to one runner.

I suspect simply connecting PCV to one runner will have a poor effect on idle. The factory Datsun sidedraft manifolds have a small chamber connecting runners 2 & 3 and the PCV is connected there. So you might try Tee-ing both of the bosses together and connecting the PCV to it. Let us know how well it works. Few have made effort to connect PCV to a racing manifold.

That's pretty much what I did.

I put a bleed screw in each runner to get an even distribution of idle air. It just makes tuning easier, give a more consistent "draw" and got the idle speed about right (bypass air). From memory I drilled it out with a 3.5mm drill after figuring out how much metal would be left and how straight I thought I could drill it.

So my idle air is more or less drawn through the crank case. It's better to have a good flow of air through there to keep the oil dry and your rocker cover clean. It also means less VOC emissions.