PVC Valve and triples

[warrenz]

Hi

 

When you guys fitted the triples what did you do about the crankcase ventilation? Currently a hose runs up to a PVC valve that connects into the intake manifold which is not possible with the triples.

 

Warren

[Toecutter]

I put a whelsh plug in it, can't remember if it was 25, 26 or 27mm but I bought all three sizes rather than going back and fourth. At the time I did get an explanation on why it is not required but can't remember atm.

 

Dimitri might be able to chime in here!

 

Sulio

[ZED660]

Get an oil catch can and run a pipe from the Rocker cover breather and another from the crankcase breather to the two inlet attachments on the side of the can.

 

[260Coupe]

Zed660 is correct.

The crank case must be vented to prevent the crankcase from pressurising (hence the term -Positive Crankcase Ventilation Valve), if you plug the crank case ventilator it will pressurise the block and blow oil.

 

Run your crank case vent and rocker cover vent hose into a catch can, catch cans with filters are commercially available or just cheat and use an old 5lt oil container with some vent holes in it.

 

cheers

 

Alan

 

[Scoota G]

Ironic Alanis Morrisette Ironic.

I just fitted a PVC valve to my JDM Manifold Running Triple Dellortos and it makes a hell of a racket as it only draws off one cylinder. 

I was going to ask the same question but now i don't have to.

 

Cheers  ;D

[Zedman240®]

Sorry Sulio, a bit late but yep. Oil catch can is the way to go. Once by accident I hooked up the crankase to the rocker cover.....Dont know what I was thinking...Had a oil leak from rear main seal then realised what I did and yanked it out!

[Toecutter]

oh might have to take that whelsh plug out, hmmm...can't remember who advised to just plug it up but will have a another look at it when I get back.

 

Sulio

[crowe]

I am just going through this process now and don't quite understand.

 

Why is it that both the rocker cover and crankcase must be vented to a catch tank? I noticed that Sulio has blocked his crankcase ventilation with the welch plug (is this still the case sulio?) and been advised against this but.... won't the blowby gas that normally comes from the crankcase now flow up the front of the timing cover and come out the rocker cover vent if the crankcase ventilation is blocked?

 

Any ideas? Is this logical? Just want to get it right first time and really dont want to plumb the crankvent if i dont have to.

 

 

 

[260Coupe]

Blocking off the crank case vent can cause blow back through the oil galleries and out through the rocker cover vent. The best and most elegant solution is to install an air box around the triples and vent the crank case and rocker cover into this airbox so any oil fumes are then burnt via the combustion process (This is the first thing that the EPA always check for if your car is ever inspected for emmsions). I have installed a cold air airbox (with 50mm ram tubes inside) from a Prince GTB Skyline which is fed via a 280Z (US version S30 with fual injected L28) air filter housing which is located in front of the radiator, the crank case and rocker cover vent are then plumbed into the airbox. This set up makes approx 10% more mid range power than straight ram tubes and has no loss of peak power (proven on the chassis dyno)....in all a very sanitary set up which looks "factory" and should appease any EPA inspector.    

 

cheers

 

Alan

[crowe]

Thanks for the info Alan.

 

What sort of clearance do you have from the end of your trumpets to the outside wall of the airbox? Do have a picture of the whole cold air intake system? Where does the 10% more power come from, the cold air intake or the ramming effect or both?

 

Cheers, Callum

[Toecutter]

That does look very factory Alan. How did the holes on the other side of the air box line up with the carby throats etc?

 

Sulio

[luvemfast]

Alan, I see that you have a return fuel line.

How is this set up?

I was looking into fitting a regulator before the carbies and not having a return line. Is this the wrong way?

[crowe]

The benefit of fuel return can be argued, i have seen triple setups with returns and without and both run no problems.

 

A return line is probably easier to manage, cheaper to setup fuel pressure and delivery correctly and has the added benefit of delivering cold fuel to your carby's. Heat soak is very much an issue on cars that run triples without a return line, the return line allows cold fuel to be constantly delivered to your fuel chambers.

 

If you have a return rail line standard back to the tank (i think all zed's do) then you are best off using it. You also dont need a flash pressure regulator using this setup, a simple restriction on the return line (brass olive or hose barb) drilled correctly will with a little mucking around get your the right operating pressure without compromising flow and full throttle conditons. You can also then use your standard pump rather than aftermarket.

 

Hope that helps

[260Coupe]

The 50mm ram tubes have approx 50mm clearance at the front carb and taper to around 20mm, the increase in mid range power comes from the plenum chamber effect (all three carbs drawing from the same enclosure and the shape of the airbox (Prince engineers designed aircraft in WWII so they knew abit about airflow)  HP was also assisted by the cold air drawn in from in front of the radiator through the 280Z airfilter housing, the air box provides better throttle response, with greater mid range torque and smoother power delivery without harming peak power.

The carby holes in the backing plate of the airbox had to be re-aligned as the Prince Mikunis are staggered at an angle so some welding and filing was done to ensure a correct fit with no overlap or air gaps. The return fuel line was run via the original lines thru a restrictor installed in the back carby T piece (brass plug with 3mm hole) , fuel flow was measured to ensure sufficient fuel was delivered at sustained full throttle (using the standard fuel pump) . The fuel lines is tempoary at the moment as I'm making up a proper fuel rail by modifying the original with larger 8mm diameter metal tubing, this will make it all very neat and tidy .

The car as at the panel shop getting an engine bay refresh, I'll post some pics of the end result in a few weeks when I get it all back together again for the road trip to QLD.

 

cheers

 

Alan