Re: How to add a PCV Valve to a 1949 Packard

Posted by Tobs On 2017/9/15 14:05:44

On the mewagner website they have a few articles on the history and background of PCVs. Most or all have 2 connections from the crankcase. 1 connection with the pcv goes to the intake manifold. This hose should always be pulling the vapors out of the crankcase to be burned in the combustion process. The second hose that goes to the airfilter feeds clean air into the crankcase after the air is filtered.
From what I learned, the PCV regulates in 2 modes. Idle mode with high manifold vacuum, closes the valve partially so that you dont suck in too much air or oil to upset the idle mixture. The second mode is cruise or low vacuum mode, where the valve opens more to suck out more blowby. Obviously both modes have to be controlled and balanced so that idle doesnt get too lean.
Re-tuning the carb at idle could be pretty easily done, but I am more concerned about the mixture and effects while driving. Obviously you dont want to reduce vacuum in the intake manifold too much.
If vac is reduced, it could cause the metering rods in the carb to change their behavior and richen the mixture. Or, the extra air from the crankcase could lean the mixture. I dont know! IF I try this, I already have a vacuum gauge on the dash that I can use to make sure nothing is getting thrown off. The best way would be to use a wide band O2 sensor so that I can monitor air fuel ratio before and after istalling the PCV. I will ponder and dream about this for a while.