Im now thinking that i hooked up the pcv on the brake vacuum port! And not on the front port. Im using a holley 750 double pumper with a proform chokeless mainbody.
I tried running both my booster and the PCV, Tee'd together, to the back port, and like I said, when I did that, the back cylinders idled lean. I supposed that was cuz on my standard 750DP without 4-corner idle, they were dry.
I put the PCV back on the front, and that solved it.
But, that cam, at just 12* timing, in my 367, idled at about 8/9 inches, so getting the idle to be consistent, I had to try several different used PCVs out of my life-long collection-box. I finally divorced the air supply from the factory air box to the breather, so that at WOT/RPM the breather dumped straight to atmosphere. I didn't do this on purpose, It just happened when I brought cold fresh air down thru the hood, and sealed the carb to the underside; there was just no place for the fresh air hose to go.
These two changes, stabilized the idle. By this time, I was already running the AirGap on my Edelbrock alloy heads. Yeah, that cam was my tuning teacher. Spent a lot of hours on it. IIRC I measured it at 249/250@050. Before summer was over, I had pulled that cam. It was just too big for what I wanted it to do.
I'm guessing that your cam is the STL4650, which is a lil bigger advertised, than the 292/292/108 Mopar hydro I ran; so we're in the ballpark.
If you have an automatic, you can get away with 21/34, but IMO at 21*, the transfer slots are gonna be too far closed, and if the two Primary blades are not synchronized to each other in such a manner that they are not passing identical amounts of air, then you will have idle problems. Well that's not true with a single-plane intake, but I'm leaving that comment in for other readers.
Furthermore,
I'm guessing your heads are closed-chamber alloys.
and for you to run that combo efficiently, the Scr needs to be at least 11.5 which means the pistons need to have a Q-pad and the quench is gonna be under 040, and if all that is true; then, detonation should be impossible.
But if you are running iron closed chamber heads, those will top out at about 10.2Scr; any higher may lead to detonation on best pumpgas.
I ran 11.0Scr/closed-chamber alloys/028 Q/ on that 292 cam, and I could not get detonation on 87E10, the only gas that 367 has ever run.
the point is that, if you are getting detonation with the Vcan working, then something is wrong. and I'm pointing straight to the @21* of Idle-Timing, which at your elevation of like 3ft above sealevel, is just too much for your air density, but more than anything; that 21* points to Not enough Transfer slot exposure..
My guess is that when you get your idle fixed, that will also cure your detonation with a working VA.
To give you an idea about timing;
my timing was 12/14 at idle going to 28* by 2800, going to 34@ 3400. and the Vcan was modified for 22*, to come on as fast as the thing could go . Thus, by about 1800 the Total cruize-timing was say; 14 Idle plus 7 centrifugal, plus 22 from the can, equals 43. By 2800 This was increased to 14 +14 +22= 50. As the throttle rolled in, the Vcan rolled out. Smooth as can be, and no detonation.
But
the thing is I have a 4-speed, so idle speed very significantly affects the slowest speed I can drive before I gotta slip the clutch; and that means my T-slots gotta be bang-on, which means the idle-timing has got to take the hit. In contrast, the automatic guys got it easy.
Btw, this combo almost always ran 3.55s cuz that is all I wanted to run; I had other gears. at that time I was running 25.6" tires, and if I retarded the timing to 5*, she would idle nicely down to 550rpm, pulling herself at 4.4 mph; not slow enough to parade with, without riding my 800 dollar clutch.
So I got me a 3.09 overdrive, and that allowed 3.8 mph, still not quite low enough. and the 292 cam hated that super wide ratiobox, and
65= 2160 was not fuel-efficient. I figured out that 4.30s would be 65=2620 and hiway economy was no lower, but now she would idle along at 550rpm=3.1 mph, so that was good. But the splits were just too much; that cam had to go.
BTW,
Without a 4-corner idle
when you reset your Idle-timing to say 14*, to enable the T-slots to function properly. Your gonna find that the exhaust begins to burn your eyes. Your gonna find, as I did, that this begins to go away, if you introduce some Idle-Air bypass.
Your Holley is not set up with an adjustable bypass, so you are gonna have to experiment .
What I did was to Tee into the PCV line and and install a short closed standpipe on the Tee, then drill the pipe with two holes beginning at 1/16 inch, and progressively increasing the holes to a max of 7/32, at which point , the stink went away. Then, I drilled my primary throttle plates, one 7/32 hole in each, up between the T-slots and the Idle-ports, and finally, put the PCV line back to stock.
Now, my engine liked 7/32. I have no idea what yours will like.
If you choose this method, and if you drill too big, the engine will run rougher. and you will need to increase fueling from the mixture screws, this will then increase the idle speed, same as if you had adjusted the Curb-idle screw. So then the logical response is to close the throttle, which of course upsets the T-slot exposure, and leads straight back to the tip-in sag, so don't touch the speed screw! Instead, you retard the Idle-Timing. But when you get down to 12 or 10, the throttle response gets mushy, and the engine is losing idle-power, fast. and
There you stand, tearing your hair out, so what's the answer?
Well, the holes are too big so take the carb off, solder the holes shut, move over, and start again with smaller holes. Then reset the carb and timing, back to basic.
My engine has had three cams, and even the smallest; 270/276/110, liked a bit of bypass.
There are at least three other ways to get bypass air from your Holley
1) you can crack the Secondaries
2) you can install adjustable air-bleeds on the tops of the wells
3) you can run a dedicated suction line to the PCV circuit, or
4) a second PCV, if your engine is big enough
I tried all but the Air-bleeds, and nothing worked as good as bypass holes in the throttles. But, I went too big the first time! that's learning. and each smaller cam, required less bypass, so my throttle plates are looking a lil funky nowadays, cuz you cannot redrill the solder slugs cuz then they fall out. Well you can if you drill a half size smaller exactly in the center of the original hole; good luck with that. But even then, I lost one.
Remember, you only need enough bypass air to kill the stinky exhaust.
btw, IDK how or why that works, to me it's magic.
Ok breakfast time!
