K engine Vacuum setup

[cibvr4]

Just wondering how a stock K engine is set up? Is it PCV valve to both brake and inlet manifold / carby? Just the one hose with a T piece?

Im having some issues with my setup not dealing wth crankcase pressure adequetly so need a starting point to work from.

Thanks

cibvr4

[oldcorollas]

umm, PCV usually goes from the rocker cover, to the plate under the carby.

brake booster should always be a dedicated line (with one way valve) going fromthe manifold itself i think (i don't have a booster )

no T needed.

if you are still getting pressure, PCV could be blocked.. take out and clean...

what about th ebig pipe fromt he rocker cover to the air filter? that should easily be able to vent any gases in the block.....
has that been removed/blocked?

[cibvr4]

Yeah stock setup has been replaced with redline manifold and twin 40DCOE's, and a custom vacuum rail has been made up. I'll take a photo and post up. I think i have found the problem though. PCV valve was in the rocker cover back to front.... Wierd thing is it's been that way since i've had the car, and today the oil pressure gauge climbed to 80psi before blowing the rocker cover gasket out! I'm soaking some new hose in hot water and about to refit and check. Will post result.

Thanks

[oldcorollas]

the PCV will not prevent pressure build up in the crank case... not really...

what about the other hose?

on early motors this goes to a pipe that just vents down toward the road. on later models, it vents back to the air cleaner. since it has no valve and is bigger than the PCV, it is more effective for venting.

this MUST be connected up or you will pressurise.

where do you have this hose going to now?

[cibvr4]

Pics attached...

Changing the PCV valve around has changed oil pressure. It now idles with approx 40psi pressure but under acceleration lifts to around 70 - 80 psi. With the PCV valve around the other way it sat on 60psi all the time, and varied very little. The gauge is a cheapie so those values could be out by 10 psi either way.

From the pics you can see that the PCV is vented to a brass rail, which takes vaccum from 4 ports on the inlet manifold. The end of the brass rail is connected to the valve (on the firewall) before the brake booster.

That second tube is connected to the filter assembly on the rear carby. I've checked both the rocker cover and the filter. Rocker cover is clear and flows freely, filter end however the filter end isn't flowing that clearly. I can blow through it but it requires a modest effort.

Looking at all this now i can't see how so much pressure built up to blow out the rocker cover gasket?!?!?! As you say, that second hose should vent more than enough pressure to avoid blowing out a gasket!

The motor is new and strong, revs beautifully to 7500 rpm. Built with quality components for rallying. Not smokey and no blow-by. Do the pressures i've quoted sound normal?

Thanks

[oldcorollas]

idle sounds a bit high, but probably ok for new well clearanced bearings (and farken cam rockers/shaft )

why should the crankcase pressure have ANY effect on the oil pressure? surely it couldn't pressurise that much? oil should piss out of main seals and around spark plug seals etc...

there should be no obstruction on the big pipe you have running to the air filter base.... air should freely flow out of that.

if this is for rally only iwould suggest to piss off the PCV,and run the brake booster only.... use the PCV hole as a second vent...
then again, if it doesn't affect your braking, then i spose leave it (although... be leaking air into the brake booster line via the PCV under vaccuum, you are decreasing the amount of vacuum/pressure that can be stored in the booster.... as the PCV will act like a bleed valve on a wastegate line... perhaps..)

purpose of the PCV is to draw air into the motor via the vent tube, and then into the manifold and get burnt... ????

[cibvr4]

why should the crankcase pressure have ANY effect on the oil pressure? surely it couldn't pressurise that much? oil should piss out of main seals and around spark plug seals etc...

Yeah, try the main seal behind the balancer. Not pissing out but i just checked and there's 4 or 5 drops on the garage floor.

purpose of the PCV is to draw air into the motor via the vent tube, and then into the manifold and get burnt... ????

Pressure is building under the rocker cover, and vaccum is present at the manifold at idle and under acceleration. The PCV is allowing the vacuum from the manifold to suck through the air under pressure from the rocker cover back through the brass rail into the manifold. Only problem is it doesn't seem to be able to do it fast enough to stop keep the pressure neutral in the crankcase. Am i missing something here? What have i got wrong?!?!?!?!!

I'm going to check that hose connection at the rear carby....... Hey appreciate u charing your knowledge in this area. Much Appreciated

[oldcorollas]

most pressure will build up under throttle from blow by, when there is no manifold vacuum.
when there is manifold vacuum, you will have little blowby.

they are different processes that occur at different times

the purpose of the PCV is to suck new air THROUGH the motor to help burn off volatiles in the crankcase... it's basically an emissions thing.

the PCV will not suck the pressure out of the rocker cover... as there is no vacuum to pull it

the VENT (the big hose) is what releases pressure from the rocker cover/crankcase... it is large diameter and ALWAYS open to atmosphere... sure it's not kinked or anything?

perhaps run that hose to a bottle for a short time and see if air is coming out of it....

if you have a lot of blowby from rings not sealing (or mixture too rich ... my blowby virtually stopped when the EFI went on and tuned to be notstinkingrich), then perhaps that pipe will not flow the air IF it is kinked or blocked or similar...

if, even when there is no hose, just the rocker cover outlet, there is still pressure building up, i would start by taking off rocker cover and seeing if the baffle has been damaged in any way... also, if oil is blocking the baffle opening at the back of the rocker cover under accel, then it may need to be modified (holes etc)...

but first and foremost... why so much blowby... and why is it not being vented by a large pipe that should be open to atmosphere....

either the hole/pipe is blocked... or you have far too much blowlby...