plugging hole on 327???

[dannies68]

I am cleaning up my father in laws '68 C10 with a mild 327. I recently installed an edelbrock intake, carb and valve covers. I recently visited a parts shop because I was having issues with my valve cover breathers and the employee mentioned since I installed valve covers with breathers I will now have to plug a hole in the block behind the distributor.

Is this true? If so can anyone give me some more info as to how and why?

[19673ontree]

No you dont have to plug the breatber , it will be fine with the rear breather and also the valve cover breather , what year 327 is it ? Because after 68 they made the big journal 327 for a while and it dont have the block breather , pre 67 does

[Russ.W.]

He's referring to the PCV system (positive crankcase ventilation?). I had to do the same thing on the 327 in my '67 Impala.

Google PCV for the specifics on function, purpose, setup, pro's, con's etc.. That'll help more than I ever could.


For my 327, I had the stock valve covers (no breather holes), with the oil cap/breather being a tube at the front of the engine, and the PCV system was a valve in the rear of the engine (near the dizzy), with a hose running from there into the front of the carby.

The new valve covers have a hole in each for the breathers. Here's what you need to do:

Remove the oil filler tube at the front of the intake, and plug it with a freeze plug. The valve cover with the hole for the oil cap (you'll need a new oil cap if not supplied with the valve covers) now acts as the oil filler/breather.

For the breather on the other valve cover, you need to insert the grommet and valve (should be supplied), and run the hose from there to the vac port on the front of your carby.

Then you need to remove the old valve from the rear of the engine, and plug that hole with a freeze plug.

Hope that wasn't too confusing.


I think this is how they did it from 68/69 onwards, which is why pretty much all aftermarket SBC valve covers have breather holes.



Here's a pic of mine before the switch. Note the oil filler tube at the front. And the thick hose running along the intake from the rear to the front of the carby? That's the PCV hose.




Here's after. Note the plug in the front where the old oil filler tube was (the same was done to the rear where the pcv valve was), and the breather valve and hose coming from the valve cover to the vac port on the carby. The other valve cover has the oil cap/breather.




Hope that helps.

Good luck!

[dannies68]

I am referring to the hold behind the distributor as this motor came out of a 64' impala.

[TBONE1964]

Here is what I would do. Kill two birds and use the hole with the original down draft tube and a modern PCV valve and call it good.

Photo courtesy of Google images.

[dannies68]

So the way it is currently set up is the draft tube hose goes into the pcv inlet on the front of my edelbrock carb and I have new valve covers that each have a breather. Will this work?

[viking427]

Yes it will work. As such it will pull fresh air in from both valve covers, down and across the forward portion of the lifter valley - thereby capturing and evacuating blowby gasses from all three regions.

Anyone wanting to run old school "Chevrolet" or "Corvette" ..or aftermarket for that matter, aluminum valve covers without holes will need to rig it like TBone says - just make sure you have a vented cap on your oil fill tube at the front and use a PCV valve on the rear hose (watch the arrows). Your 63/64 PCV design has the engine burning "blowby (uncombusted fuel/oil vapors) that build up in the lifter valley by pulling fresh air in from the vented front oil fill cap, via vacuum, rearward across the lifter valley, and up through the rear vent/PCV valve into the carb base/intake, where it mixes with fresh fuel/air mixture entering cylinders for combustion. Chevy's next PCV design (65/66/67'ish) reversed this by pulling the fresh air in from the rear & forward toward the front, up and out the fill tube via a hose/PCV to the carb base. The 68+ design improved one step further by now pulling fresh air "sideways" across the engine to also evacuate (capture blowby gasses) both valve covers AND the valley - which is when we begin seeing vent caps and PCV's/carb hoses on the valve covers.