AFR misleading? Plugs tell a better story?
Why do you want to pull the PCV off the primary side? I'm not familiar with that particular carb, but most any Holley from the beginning used the rear port for PCV and a port in an intake runner to power the booster. Just curious as to your line of thought here. Not saying you are wrong, just want to work through your thinking.
The short answer is;
Reason #1; my experience;
Every time I have run the PCV to the secondary side,on a dual plane street engine, that requires idle bypass air,and does not have a 4-corner idle; ( about 99% of my tunes,lol, I get idle-tuning grief, which is right away much reduced or gone when I reroute that hose to the primary side.
The longer answer;
My conclusion was that the 6 and 7 cylinders were idling lean. I don't idle-tune with an AFR, and for me reading the idle tune on the plugs is hard. But I can darn sure tune by the hesitation or stumble on Tip-in. In my personal combo,I like to run as little pump-shot as possible, cuz you know, I'm always trying to drive further on less fuel, but my right foot doesn't co-operate so much. And because it's a 750DP, so every lil bit helps. So then I am forced to work the tip-in differently.
When the combo is an automatic with a hi-stall, this is less of a deal.
But with the OPs 3.23x2.66 manual trans starter gear, the sub 2000rpm zone has to be tuned pretty tight, cuz 2000 is still only about 18mph. I can't be lazy. With 10/11 to 1 starter gear, I could be, but everyone comes with small street gears.
I only tune SBMs, and all the cams I have tuned run between about 220 and 240, (Except two were bigger), because that is all I know, and they are in my comfort zone, and I get paid, (OOPs used to get paid; now semi-retired) to get it right. And this leads to;
reason #2, the reward
When I get it right, the smiles and hugs are worth so much more than just cash.
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As to the plumbing the booster;
I have tried several times to run the booster off that rear runner, and obviously it will work...... to a degree.
But I have found that there come times and situations when the booster (not all boosters) is being manipulated during braking, and the one runner cannot keep up. Since the OPs carb has all the ports he needs to save aggravation, I jumped on it.
Yeah, I know, that was my thinking too; pressure in the intake should be equal in all directions; and in the plenum maybe it is. But in an individual runner with a performance cam, the moving piston is wreaking havoc in the runner. So I reasoned that the vacuum in the plenum, might be just an average,but that when the piston connected to that runner is driving fuel-charge back up into the intake with the late-closing valve still open, well I had to put a vacuum gauge on there. After that, I have never again used that runner. It might work for some guys with some boosters, with some combos; But not for my combo with my aggressive driving style. It seems to work just dandy fine when you rev it up, and the vacuum rises. So if you have big-number rear gears, I suppose it would be just fine.
Those are my thoughts; I too could be wrong...
But no one has yet complained, so I got no feedback data ,lol.
