Is there a known threshold beyond which venting the crank case via the valve cover becomes inadequate?

Context and background

I have a newly built BPZ3 (vvt) which has dyno time only on it at this stage. After returning from dyno tuning, it developed a profuse leak from the rear main seal which has since been removed, inspected and replaced, resolving the leak (for now).

The seal itself was removed carefully and there was no obvious damage, fault, or reason for it to be leaking.

The engine is producing 460whp, and the engine builder has suggested that the my attempts to vent the valve cover may be futile due to insufficient capacity in the oil/air passageway between sump and cam cover, leading to pressurization of the sump and seal failure.

More on the engine:
Supertech 9:1 pistons with Wiesco rings
Valve cover has two 10mm holes in the baffling and two 10AN vents to a catch can

Of course, the seal could have failed for any number of reasons, but is it likely or possible that crank case pressure was involved?

 

Hook a pressure sensor up to the dipstick tube and take a log during a pull. 460whp is a big number and on the fringes of common knowledge.

Running the ex side port through an air oil separator and then to the turbo inlet after the air filter can help increase flow. The ID of all of the fittings and hoses needs to be maximized.

Oh, and if you are swamping the drain holes between the head and the crankcase, no amount of venting will help. There are 4 of them, and they are large.

 

You've done the 'tiny hole' mod to the VC?

If the dipstick is not popping out/loose, I'd be surprised if the CC pressure was sufficient to push the seal out, but ...

I'm in a rush atm, so haven't checked, what are the chances high oil pressure (shimmed pump?) is leaking past the bearing and can only escape past the seal? IOW the seal is fine, but it just can't handle the pressure/volume?

 

Thanks Ted, the information about the large drains from the head back to sump helps. The fittings from the valve cover are weld on 10AN x2 with same size hoses to a catch can that also has the same size fittings and a 2.5in filter vent.

The dipstick hasn't moved which weighs against crankcase pressure being the problem.

I don't know about the 'oil past bearing' idea - but the pump is VVT + two shims, so has higher pressure built in.

Tiny hole mod: yes drilled out to 10mm and a second hole at 10mm added next to it.

 

Ha! I did have an analogue boost gauge hanging about but sold it. I will see if I can rig something up.

 

I know this doesn't translate directly to the 1.8 but mazda's turbo'd B6t in the 323 had a crankcase vent / breather / vapour seperator drain setup that was dropped for 1.8 engines.




the 'pot' has a small hose that iirc feeds to the turbo's inlet to vent pressure.


crancase vented by oilfilter & oil drain back to sump.

this engine was from an old rallycar and had been removed 20+ years ago.

can you get creative & install a port in the cylinderblock to vent (drill & tap etc.)

also, theres a blanking-plug in the oilpump case where a dipstick tube would be fitted in transverse / fwd installations, it's ~ 3/8" / 10mm but maybe helpfull as a test to relieve crankcase pressures?



Rich.

 

it probably would not have worked anyway, as you are looking for measurements in about the 0-2psi range. One psi is enough to cause every seal to leak.

As far as the fittings, it is the ID you have to watch. For example, the ex side port on the VC needs to be drilled out to support the ID of even an AN8. There are NPT to AN adapters out there that will take a 1/4" npt to 10AN. I frequently see such fittings used on catch cans. You can lose a ton of flow through a fitting with a small ID.

 

This is how it is set up. The cover is drilled to accept the male 10AN weld bung. The original exhaust side vent is welded up.

 

Looks sorted and well done.

 

Came for pictures of rods ventilating blocks, stayed for the nice catch can setups.

 

Another way to test for internal pressure is drill and tap a hole in a spare oil filler cap . Attach a small hose barb fitting there. For a gauge I stumbled across using a gauge for a blood pressure cuff. Cheap, very accurate, and can easily read less than 1 psi.

 

The Australian - A lot of nice install touches on that. Keep up the great work.