Big Dave

Are your intake gaskets stock or made custom from store-bought gasket material? I haven't seen them in that shape before.

AO

Those are custom gaskets from DR. Not sure what the material is, but they seem to work.

Bill Ball

Andrew:

Here's Andy's plate. Doesn't leak, but see what I mean about the filler? The filler and breather hose attach to that little spout.

AO

I'll take pics of mine when I get it off along with the new one for comparisson. Too bad we have to pull all this crap off becasue of one silly issue like this. Oh well. I'm having fun!

Bill Ball

The gasket material is non-compressable and looks like linoleum. Somebody will provide the technical info on it.

AO

Linoleum is a good description.

Bill Ball

Or in my case for smog testing. But I was planning on installing an intercooler and revising this filler plate anyway.

I'm probably just going to cut out that tiny spout and braze in some 3/4 or 1 inch copper plumbing elbow and pipe and fasten a smaller plate about 1 inch under the current plate to act as a baffle.

AO

smog testing = silly issue in my book too!

Flott Leben

Andrew,
Thanks for the updates. We all benefit when you bring issues like this to the board's attention. There are a lot of smart people on this board and the more input, the better the final product will be. This is a minor, minor issue in the grand scheme of Dave's SC kit and installation. It is also great to see Dave, as usual, step up and take care of things right away with a solid solution.

It does seem like a good amount of oil was being pushed up (and out) to that plate.

Bill,
A larger diameter breather pipe will certainly take some pressure away from that plate's gasket, will it not? But it wouldn't reduce the volume of oil making its way up and out of the crankcase, would it?
I'd be very interested to see your final baffle design. Thanks.

Bill Ball

A larger opening and pipe would reduce the breather outflow velocity and pressure while increasing the amount of oil it would take to occlude the opening and pipe. This would increase the likelihood that oil could drip back rather than be blown out the breather. When cruising above 160 MPH and averaging 145MPH, I lose more than a quart of oil in 80 miles out of that breather while none out of the cam cover breather. At this point I have a long breather hose that exits under the car and creates a horrific mess. I could put in a catch can, but quart-size are hard to fit in the engine compartment.

I am concerned that even with a bigger pipe and a bit of baffling, that under the conditions of open road racing, there are no periods of negative pressure to allow any dripback at all anyway, so I won't accomplish much.

Where else does the lower crankcase ventilate? Nowhere, right? That seems to present a problem under extreme driving conditions. Maybe I'll just have to get off the throttle once in a while.

Flott Leben

Exactly the point I was driving at. A larger pipe and baffle may help to reduce some pressure but will still not return the "caught" oil. As you said, at full throttle it would be difficult to get negative pressure that would allow oil to backflow at all.

Probably not a new idea, but . . . what about a second small oil pump (but electric) to periodically pump a smaller catch can/seperator's oil back into the crankcase? Maybe a self-priming peristaltic pump?

I think that is correct. Preventing all blowby is probably next to impossible (even if done at the engine design stage - which is too late for us anyway). What we need to do is vent the crankcase efficiently and adequately to prevent any pressure buildup. But where else could we tap into the crankcase to run a vent line to a seperator without causing more harm than good? I need to look at the engine diagrams again . . .

Jim bailey - 928 International

the lower crank "vents" into the camshaft housing as well ...up the oil return passages cast into the block. So again oil drain back is swimming upstream against the flow of vapor gasses...

Namvet

I think that is correct. Preventing all blowby is probably next to impossible (even if done at the engine design stage - which is too late for us anyway).

The 928 was not a supercharger engine design. Blowby of rings and piston lands is not the engines fault. Maybe blower pistons are available somewhere. Check them out. Normally aspirated such as it was designed for..This is a sweetheart engine.

JMO, but who needs a supercharger on a Diamond.!

blown 87

Most types of hard driven artificially aspirated motors that are designed as normally aspirated motors will have this problem.

I have been thinking about this problem for about a year now, and to me the main problem is getting the oil out of the catch can back into the motor.

I have found a valve off of a turbo Volvo that should work on the crankcase vapor line and I can get a small pump to pump the solid (coalesced) oil back into the motor.

Not real sure if I would need some kind of switch to turn the pump off and on, but I think it can be done.

I am sure you guy can tell me why something like this wont work, in fact I hope you do and save me the trouble of making something that wont work.

blown 87

Sorry, I guess I should have read your post before I made mine.

That is what I have been thinking.