23 replies to this topic

[Minigman]

Any suggestions for a catch can set up?

Obvious ones are the under wing MED and Swiftune but I’d like a engine bay set up ideally. Any pictures of yours please? Loads on eBay and other websites like Merlin and Demon tweaks etc. but looking for what works well.

Edited by Minigman, 14 August 2020 - 05:31 PM.

[kit352]

You can almost do anything you want with these. I usually pick mine based on style for whatever im doing. More money doesnt neccessarily translate into a better product with these either.
The one on one of my cars is a used soda bottle with an inlet and outlet and some steel wool on the bottom. Works perfect and fits the car.

[nicklouse]

How do you want it to work?

 

the MED and ones similar are not really suited to road use.

[Minigman]

How do you want it to work?

the MED and ones similar are not really suited to road use.

I just need to catch the oil that comes from my rocker cover breather at higher revs. Usually after sitting at motorway speeds for prolonged time at 4500rpm +. The transfer case and timing cover ones don’t tend to leak anything.

An odd thing happened yesterday when oil came up through the rivet on my rocker cover. That’s a first for me.

Edited by Minigman, 14 August 2020 - 05:05 PM.

[nicklouse]

Like I said it depends on what your set up is. You don’t say.

 

you should not really have a rocker cover one and the others should be plumbed into the carb/inlet which then pulls air through the filler cap, an extra breather on the rocker defeats the whole set up.

[Curley]

Breather to atmosphere are frowned upon these days but from what you write I'm not sure you need the rocker breather. Delete it and save the bother. 

 

On the road cars they feed the breather(s) back into the carburettors to be burn off any hydrocarbons. This was primarily done for emissions reasons but it also has the benefit of creating positive negative crank case pressure - gases are being pulled out from under the piston. As the revs climb and pressure under the piston increases. The breathers give those gases somewhere to go. Try taking the filler cap off on an idling engine and you will hear the note change.

 

The race cars you see with the MED kit on are worried less about the environment and more about keeping oil off the track while maintaining the ability of control crank case pressure.

Edited by Curley, 14 August 2020 - 06:28 PM.

[nicklouse]

You mean negative crank case pressure. 

[Ethel]

Positive Crankcase Ventilation - you're pulling fresh air through it, not just   letting the fumes waft out if they like.

[Minigman]

All mine are currently open vented with K&N filters on. Running twin HS4s on Maniflow inlet. I’m not sure if the breather hose can be plumbed into it.

[nicklouse]

All mine are currently open vented with K&N filters on. Running twin HS4s on Maniflow inlet. I’m not sure if the breather hose can be plumbed into it.

Unfortunately the worst set up you can have I’d you are worried about oil splash and smell and leaks.

[Minigman]

All mine are currently open vented with K&N filters on. Running twin HS4s on Maniflow inlet. I’m not sure if the breather hose can be plumbed into it.

Unfortunately the worst set up you can have I’d you are worried about oil splash and smell and leaks.

Why is it the worst Nick?

What do you recommend?

Built as a track day car but gets used on the roads so bhp was always a target. Running 95bhp currently.

Edited by Minigman, 14 August 2020 - 07:37 PM.

[imack]

My 1380 has 3 open to atmosphere breathes.
A fairly rare early austin 1300 factory open breather on the transfer housing, a home made 5/8" steel gauze filled oil separator on the MED timing cover and a 1/2" gauze filled oil separator on the rocker cover. Vented filler cap is plugged and sealed. Can't say I've ever noticed any oil smell in the car and I don't get any misting around the breathers even after plenty of 8000 plus rpm.

Edited by imack, 14 August 2020 - 08:15 PM.

[imack]

My 1380 has 3 open to atmosphere breathes.
A fairly rare early austin 1300 factory open breather on the transfer housing, a home made 5/8" steel gauze filled oil separator on the MED timing cover and a 1/2" gauze filled oil separator on the rocker cover. Vented filler cap is plugged and sealed. Can't say I've ever noticed any oil smell in the car and I don't get any misting around the breathers even after plenty of 8000 plus rpm.

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[Minigman]

Thanks imack. I can’t say I ever smell anything but just the rocker cover vents a bit of oil at high revs. I have a hose connected to a hooked breather pipe on mk1 type rocker cover with a K&N on the end. It drips after a while and makes an annoying mess, hence why I thought about a catch tank.

[imack]

Problem I see with these type rocker covers is you've got no oil separator so you end up with an oil air mixture in the filter rather than just air and then oil dripping out as you've experienced. I don't really know how to get around it short of fitting a non breather rocker cover and just rely on the other two breathers.
I looked into the MED type catch can a while ago but they must just end up filling up with oil as there's no form of oil separator or baffle.
I ran a catch can years ago taken off the factory timing cover and transfer case breathers. It used to fill up with filthy condensation, personally I wouldn't use one again if I could avoid it.