dharris45

The C2 327 engines, at least 66 and 67, vent the engine in two places. From the oil filler tube through the PCV valve to the base of the carburetor and from the rear top of the block to the air cleaner base.

My question is are both of these necessary?

The reason I ask is non-corvette question but related. I just purchased a 1965 El Camino. It has a 83/84 350 engine that is dressed like a 65 Chevelle/El Camino L79. So It has the vent from the oil filler to carb base but not from the back of the engine to the air cleaner. The air clear base has an opening for the vent tube but it has been taped over.

I'm not all that familiar with the 350 engines, but I believe they all had some sort of venting from the valve covers.

Am I OK with just the PCV venting on this engine?

Thanks,
Don

Duck916

Generally, no. You need a path for air to get into the engine as well as the path pulling air out (which is what you have from the oil filler to the carb).

If you want to keep this looking like a '65 motor, you will need to come up with a hidden breather. Lots of folks have put one at the rear of one of the valve covers.

LB66383

Duck916 is correct. The carburetor is sucking the air out of the crankcase through the oil filler/PCV valve. That air has to be replenished. The '66-67 system is supplying filtered air through the air cleaner and into the block. You need to duplicate that somehow -- easiest is a breather with a filter on one of the valve covers.

GearheadJoe

I agree that a filtered, fresh air intake port needs to be added. Assuming that you want to keep the existing block that lacks the rear crankcase vent, there are several different solutions that can be considered. Following are some solutions I have seen (and may have photos of on a different computer)

1) Add a vent in the side or end of a valve cover and attach it to the filtered fresh air intake port on the air cleaner base.

2) Purchase an aftermarket valve cover that has this added vent but otherwise looks like the factory midyear valve cover (can't recall the vendor's name).

3) Use the 1968 Z28/LT1 valve cover that has the vent but looks a bit different from the C2 cover. However, it's still a handsome valve cover.

4) Drill an intake hole through the intake manifold just behind the carburetor, where the hole will go straight into the lifter valley.

Note that all of these options provide a fresh air intake port that connects to the air cleaner base. The exhaust port will remain as you have it now, from the oil fill tube, through a PVC valve, to an intake manifold vacuum port on the carb.

Most people recommend putting some sort of baffle on the fresh air intake port to prevent oil droplets from being pushed out the intake port under certain conditions such as high rpm operation. I'm not sure how important this is for the intake side, but it's probably a good idea to include the baffle.

ukcraig

GearheadJoe

Yup, PML is the vendor whose name I could not recall.