1965 Corvette & Others with Small Block Chevy

ZZ4 with Corvette Script Valve Covers

Replacing your 327 with a newer Small Block Chevy is fairly easy, mainly swapping parts and installing. It can get a little more difficult base upon heads, headers, intake, pulley system. But in all cases you need to have a Positive Crankcase Ventilation (PCV) system. The 327 had a Crankcase Ventilation Hole at the back of the block that was eliminate somewhere around 1968. There have been MANY solutions for the same problem. At the low or easy end is use NEWER valve covers with PCV valve and breathers. BUT if you want to keep your Corvette Scripted Valve Covers you need to be a little more creative. Here there have been a variety of solutions, some of the most common (1) Drill and add PCV valve and breather to valve covers (2) Drill/tap back of block for PCV valve and breather on oil fill tube. (3) Drill and add PCV valve in back of intake manifold and use breather on oil fill tube. There are other but I think those are the most common.

1955-1968 Block with provision for Vent Tube

Below is a '65 327/365 with a not stock carburetor but the PCV system is what we are looking at. At the back of the engine is the INTAKE to the system. Air enter here through the Air Cleaner and is pull through the block exiting via the Oil Fill Tube and into the base of the carburetor. NOTE: On this setup there is NO PCV valve but a small .090 metering block in the rubber hose. On '66-'67 there is a PCV valve at the Oil Filler Tube.

Below is one of the common solutions with stock intake manifold --- PCV & Baffle


Here is another with hole drilled in valve cover

Normally you could, as explained above, drill manifold and insert PCV valve and add breather to oil fill tube BUT My challenge was (1) small and limited space on the dual quad manifold (2) Carburetor port is on front of front carburetor. Below is my solution, starting with getting the correct fitting, I selected one a 90 degree with 5/8 Hose and 3/8 NPT pipe fitting. Input should be big and have plenty of room to breath. I then measured, measured, measured making sure I could screw the fitting in and it would not interfere with distributor. Then carefully center punch, drill & tap (did a practice runs on wood then some 1/4" aluminum plate). Screw fitting in and build a baffle.  Baffle is just a small piece of aluminum cut to fit couture of manifold and attached with self tapping screws coated with thread-lock. Then using 3/8 aluminum brake line and some 3/8 ID rubber hose just bend to fit limit space and route to back.

Now you can use your scripted valve covers J

Click on image for larger view

Fitting & Tools Measure, Measure, Measure Center Punch & Go For It Drilled & Tapped
Drilled & Tapped Underneath Baffle Baffle
Baffle Baffle 3/8 Tube Tube Routing
  Tube Routing Final Solution  


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