Oil Catch Can

[mikesr]

Has anyone fitted one?

I had the O/S airbox off last weekend and the amount of sludgy oil around the number 1 intake was quite impressive. It may explain why that intake sucks so much more air than the rest of the bank if its being gummed up with sludge and held open slightly.

I googled a report from a guy who had put a catch can on a datsun. He found that the intake vacuum was actually collapsing the pipes he had fitted. So he disconnected the hose to the airbox and fitted a filter on the catch can outlet. After whih very little oil was collected in the can.

But: -
1. It will fail the MOT - the vent has to be into the air intake I believe.
And
2. What about PCV valves and all that (Positive crankcase venting)
I read somewhere that its beneficial to actively extract the vapours from the crankcase.

So I was thinking of fitting a can to reduce the oil getting into the air box but still connect it up to the airbox.

Any experiences anyone has had fitting one or any comments from the experts on use of a catch can much appreciated.

Mike

[cossiemetro]

its not really enviromentally friendly but putting oily fumes in the inlet is not good for the car either best to have a proper breather tank and empty it if it builds up rather than venting into the inlet most performance cars especially 350-450 cossie's need a proper breather system

[350matt]

sounds like a good idea to me, As you can restrict the airflow back into the airbox,
might give it a go myself

MAtt

[mikesr]

After a quick look at the crankcase breather it doesn't appear to have a PCV valve. I thought they were needed to reduce the vapours drawn into the intake at idle and stop blow back into the crankcase. So not feeding it into the intake would be a good idea.

I found a nice s/steel can with two inlets and a filter here. This could take the hsoe from the 4 way and the crankcase one.

I think mounting it on a plate bolted to the top of the cam cover in front of the water pipe might work. Just gotta reduce the crankcase breather from 22ish mm down to 1/2 inch and the 4 way from 6mm up to 1/2 inch. The plumbing will cost as much as the can

Edited by mikesr on Sunday 12th November 15:50

[diycerb]

Hi,

I've been thinking of doing this for a while. Looked at the Mocal oil separator but couldn't see where it would go nicely. The one you found looks really good.

Was considering making extra crankcase breather vents in the rocker covers towards the rear of the engine, which might help reduce crankcase pressure further. When we fit breathers to cossie's they have three vents, two block and one rocker cover and thats only a four cylinder motor.

Rich.

[jon h]

There was a Cerb I saw at Cream last year with one on, he'd fabricated it at work in stainless steel. Can't remember his name, but was from Derby, dark blue car with newly re-built engine in red.

Jon H

[mikesr]

Just been trial fitting a cardboard tube of the correct dimensions.

It looks like it will fit in front of the water pipe just inboard of the airbox on the off side. A horizontal plate bolted onto the top of the cam cover would be just about the height of the bracket on the can with it sitting with the filter clearing the bonnet.

(Mines a 4.2 and there aint a lot of free space to play with so I couldn't say if it would fit a 4.5.)

Anyone know what exactly the hoses from the intakes into the 4 way actually vent?
I know the hose at the rear goes to the carbon cannister in the rear N/S wheel arch.
But if the 2 hoses don't connect via some internal passageways to the cam boxes then there isn't any vent for them at all.

[diycerb]

The two pipes connect to the two galleries that run along the top of the throttle bodies, one on each side. The 4 allen screws on each side screw into these galleries. If you take an allen screw out there is a small orifice underneath each. On side is the gallery leading to the tube and the other side goes into each inlet port.

Not totally sure what their for, my allen screws are not wound down hard. Did wonder if it was a idle air adjustment but would have come to light before now if it was.

Maybe someone knows, there is a similar arrangement on 4.5 throttles as well.

Think I might order one of those catch cans, might make a cardboard one up first to check fitment.

Rich.

[mikesr]

Looking at the engine rebuild manual it seems the cam boxes and the front of the engine are connected anyway as the cam chain runs up into the ends of the cam boxes of course.

And from the sounds of it the hose from the 4 way is venting fuel vapour. Which is sounding familiar. I vaguely rember a conversation with Trackcar about it.

One of his mods is to remove the hose from the 4 way to the air box and replace teh 4 way with a 3 way. I guess it will upset the fuelling on the even bank if its sucking fuel vapour in. Likely contributes to the lumpy running at low revs.

I wouldn't want fuel vapour venting into an oil ctach can that was open to the atmosphere via a filter.

So revised plan - connect a catch can up to the crankcase vent and remove the 4-way-to-airbox hose.

Thus don't need a duel inlet on the catch can so an alternative is here

The mini one looks suitable. And there is a s/steel P clip available for mounting it.

Edited by mikesr on Sunday 12th November 15:43