[Walt Fricke]

"I know nothing for fact, but I have done it before and it worked great. " Diogenes would have shouted "Eureka" if he had met you.

I have an intake valve cover with a hole in it, and have idly thought of machining it some and fitting a piece of clear plastic into it just for peeking in while the car is in the garage. I suppose one could rig up a camera (so small and cheap these days) to video while on the road or track if you trusted the plastic (use glass?) and the seal. Cheaper than a Spintron.

From posts here and there I have learned from others that you can pull the cam chain box covers and idle the motor and watch the chain jump up and down without causing too much of a mess.

But that if you try that with a valve cover off you will create one hell of a mess.

The crank case and the oil tank both need a way to access atmospheric pressure, either to avoid a vacuum or to vent excess air (mostly) pressure. How to do this?

The crank case uses the hose to the top of the oil tank. Didn't the MFI and Carbed cars just plug into the filtered air side of the stock air filter system?

Similarly, the CIS and later systems did not have a separate filter for this purpose. Rather, the early CIS connected to the air box in the area above (clean side) of the filter. So only filtered air could get into the engine and oil, and any vapors (or excess oil) from the crank case and oil tank would go into the intake system.

At some point (by the '80s SCs anyway) this point was moved to the rubber boot between the metering side of the CIS intake and the throttle body. This is why taking the oil tank cap off of an idling motor of this era produced an increase in RPMs - air was bypassing the measuring plate.

But I'd not want any of that stuff into the intake of a race motor.

Nonetheless, there is enough positive crank case pressure to force a lot of oil vapor out of a hole in the chain cover, as my experience demonstrated, so I haven't been eager to pull a cover there and run the motor just to see.