Should my Crankcase be Vented??

dmfconsult · #1 (**permalink**) 06-04-2003, 11:21 AM

I have about a 1985 302W that has aftermarket valve covers. One cover has a non-vented oil cap on it and the other valvecover has a cap with a hose connection tree that is all sealed off. I am finding after driving, oil is blowing out of the cap seals (not a lot but it is an irritation). I have seen many sbf's with a gas-line size hose going to the carb. plate. Should I get a hose to the carb plate? If so should it be on one or both valve covers.

Thanks,
Dave

jayhawk261 · #2 (**permalink**) 06-04-2003, 11:24 AM

You need to buy a couple of breathers. One will be a standard breather and the other will be for a PCV valve. The hose you see going from a breather to the carb base plate is the from the PCV valve. There does need to be an outlet for built up crankcase pressure. I've even seen some breathers blown out of their holes.

Ron61 · #3 (**permalink**) 06-04-2003, 11:32 AM

What Jayhawk said above. Plus the breather cap on the drivers side usually has a hose going to the air cleaner which pulls the fumes and oil mist out of that side and keeps them off the motor.

Ron

trularin · #4 (**permalink**) 06-04-2003, 11:35 AM

You need to have the crankcase vented. At the base of the carb ( or somewhere else ) there will be manifold vacuum. Connect the manifold vacuum to the PCV valve. This wil draw the air from the crankcase.

Since air is leaving, fresh and clean ( we hope ) air wil be arriving. Put an air cleaner or breather to the vavle cover.

The reason I say air cleaner is that some people use the stock air cleaner which has a tube from it about the 1/2 " .

Hope this helps.

Trularin

what part of Detroit?

jayhawk261 · #5 (**permalink**) 06-04-2003, 11:40 AM

dmfconsult: I got yor e-mail but can't reply directly right now. that's my home address and I'm at work. You know, firewalls and all.

If it were me, I would buy two new breathers. They are relatively inexpensive, $7 - $15, and I treat them like a wear part. They do fill with oil eventually and they don't work as well after that. Mr. Gasket, Moroso, and any number of other manufacturers will have what you need. As far as a PCV valve goes one from a 79 mustang V8 has just one hose oulet (if I remember correctly) and will probably look the cleanest.

jayhawk261 · #6 (**permalink**) 06-04-2003, 11:45 AM

Sorry, posted it twice!

dmfconsult · #7 (**permalink**) 06-04-2003, 11:56 AM

Thanks for all the feedback! I posted this thread about 30 minutes ago. I usually don't get this many replies in 2 weeks. Did I miss a holiday today or something?? Trularin, I'm in Northville area,

Cheers!!

Jack21 · #8 (**permalink**) 06-04-2003, 04:42 PM

You need a vented crankcase, actually a forced ventilation crankcase to purge oil vapors from the crankcase, and keep the crankcase under vacuum. The oil fill needs to be vented to let air in. Some vent these to the air cleaner through a hose for filtered air. The opposite valve cover has (or should have) a PCV (Positive Crankcase Ventilation) grommet or fitting. The PCV valve typically has a 3/8" hose connection that uses 3/8" fuel line hose to connect to a 3/8" fitting at the rear of the Carburetor. This distributes crankcase vapors evenly to all 8 cylinders. DON'T connect this to the #4 cylinder fitting on the intake manifold. This fitting needs to be connected to the power brake diaphram. If no power brakes, the fitting needs to be plugged with a pipe plug.