When running a car in...

[RedMist]

FWIW, my 4age makes a ticking noise from the head when cold, until the oil pressure comes up. When I open the oil filler, it blows a little air out, a few specks of oil too, but I noticed that the oil breather hose is quite perished/blocked.

I'm going to get a catch can, I realise reducing the pressure in the crankcase may lessen ring seal and lead to a little more exhaust smoke, but from what I've read, having no oil vapour into the intake raises power very slightly, and will hopefully stop my motor from leaking oil from the cam covers and sump seal. Does that make sense?

I believe that on a good running engine you should acutally loose HP. Its a case of actually sucking air out rather than just letting it vent. If you can run the crankcase in a vacuum you gain HP, as there is less air interferance with the crank/pistons/rods. Hence the excavator systems on old racing V8's and the pumps on non dry sump cars. Race cars run a vented can either because the ECU doesnt self tune for reduced octane or in the case of the bigport 16 valve tight turns at high RPM forces oil out the breathers.

[RS13]

So I'd be better off with a baffled catch can and a sealed system? Basically have it running from the cam cover, to the can, through the baffling, back into the intake? But that wouldn't really solve my problem. I dunno.

[RedMist]

Personally I would stick with the stock system. Unless your engine is more than a little over the hill, you are going aftermarket ECU or you are intending to corner it very hard. (or its a bigport with the stock breathing/ oil return system, and you are intending to keep it very high in RPM)

[RS13]

Yeah. The current 10mm breather hose I've got has a 6mm restrictor hose inside it? I continually find it gunked up, so I've got a 10mm hose, hopefully that solves my pressurising problem?

[jondee86]

Kind of interested to hear what the final diagnosis is on this one

Since new rings have good tension and a small end gap, they will seal
effectively, and blowby will be negligible (assuming they are properly
bedded in ). As the rings wear, they will lose tension, the end gap will
increase. Sealing is less effective and blowby will increase. Some of
your exhaust will be leaving the engine via the crankcase and out the
breathers !!

On well worn engines, the pulses caused as each cylinder fires and leaks
gas into the crankcase, can be felt if you put your hand over the open
oil filler hole.

On single cylinder engines crankcase compression occurs as the piston
moves up and down, forcing air in and out of the crankcase breather.
However, on four cylinder engines there are always two pistons going
up and two going down, so the air is just displaced from one part of the
crankcase to another.

Cheers... jondee86