Crankcase breather question
Never mind, i just remembered my edelbrock carb has a separate manifold vacuum port. Day has been too long lol
The PCV does not get connected to any old port. It must connect to the port designed for it which dumps into the carb base, between the idle discharge ports; do NOT use the powerbrake port , if you do, you will have distribution issues. Also; do not tee the power brake hose together with the PCV. Don't Tee anything into the PCV unless it is a fixed-orifice idle-bypass air.
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Here's some rambling thoughts;
on both the 292 and the 276 cams in my combo,
Once I got the transfer slots working right, the idle speed is controlled with timing. The more timing you give it, the higher the idle will go. Until you hit some pretty big numbers, which you can't run with every engine because of detonation. Nor is there a reason to, but that's a different story.
So now the transfers are working and I got the idle speed set. But depending on the combo, the engine may want more idle air, to smooth it out and to cure the stink in the exhaust. IDK what that stink is, that burns my eyes; I just know it goes away when Iget the idle air bypass working right.
So now with the bypass air worked out, the idle speed may have increased to an unpleasant high, so the only option is to retard the timing, back to a decent idle speed. But occasionally it happens that I gave it too much bypass air, and she won't idle down enough yet still have snappy timing. I mean it happens. So then I have to go back and take some of that bypass air out, and put timing back in. And so, back and forth it goes, until I hit the sweetspot.
But this sweetspot is different for automatics, than for stick cars...... cuz stick cars have their engines married to the tires, unlike the fluid coupling that autos enjoy.
Stick cars with high compression and anything bigger than about a 268* cam, will get real jumpy at low rpm, in first gear, with what I deem too much timing. This severely limits the lowest speed that you can drive it. And the reason for this, I have surmised , is that the power pulses are just too early and too powerful. And this behavior is instantly cured by retarding the idle-timing. I just keep retarding, and the idlespeed keeps dropping, and eventually the engine will stall; well that's too much retard,lol.
But if you get your carb's low-speed circuit working right, and the bypass air sized right, then even my 292/292/108 cam would idle down to 550 in gear with a starter gear of 2.66x3.55=9.44 (stick-car), with the idle-timing retarded to 5*. She would happily pull herself around the parking lot at 4 mph. I just can't turn, cuz she couldn't overpower the SureGrip.
Imagine what the idle vacuum was at 550, IDK what it was, that was year 2000.
Now imagine what the PCV was doing. IDK/ don't care, cuz she was not affecting the engine.
Now, come time to accelerate a lil, the hi-compression engine takes throttle quite willingly even at 5* idle timing. It ain't snappy, but at 4mph, we're just parading. I had a 750DP on that engine, and it had no hesitations or bogs. I don't recall ever nailing the gas at 550rpm/4mph/5* timing, so can't say how unhappy it mightabin about that, but that combo did spend a lotta time happily parading.
The point is this; most guys will tell you to run waaaay more idle-timing than necessary. Some will even tell you to set it with a vacuum gauge.
And if you have an automatic trans, you can get away with murder as to timing.
But you absolutely cannot get your transfer slots synced up, AND, get the bypass air set right,AND have a satisfactory idle-speed..... if you follow that advice. You can make it work, with the TC sucking up the herky-jerky, and the higher the stall the more you can get away with.... But I just gotta ask why? Below the stall, your engine will never be asked to work hard, so why does anyone care what the timing is down there? Why does everyone recommend numbers like; 18,20,25 degrees even?
I got an idea; why not let the engine decide what it wants.Whenever I do this, the idle timing comes in at 10 to 16.
So when I begin my tune, I just start in the middle.
But here's my back-up plan; I always start the tune with the transfer slot exposure a lil taller than wide. So if I can't get a low-enough idle, with a decent timing..... then I back off the speed screw, just a lil, and start over. Of course this also reduces the fuel delivery, but at this point, I can usually get what she needs from the Idle Mixture screws.
How do you know if your street combo needs bypass air?
Ok first, the biggest cam I have tuned is the 292/292/108, So I cannot speak to anything bigger. Then;
Easy; retard the idle timing to 14*, Making sure the Vcan is NOT working. Then adjust the rpm to 700N. If your exhaust is now stinky, you need bypass air.
If an automatic; lock the brakes and put it in gear. Reset the the idlespeed to 550rpm. Put it back in Park and check the rpm rise; If more than 150 rpm, you need bypass air.
If the rpm rises more than 250 rpm, you need a new or higher stall TC, or your engine is torque-handicapped,aka gutless.
Between 50 and 100rpm rise, is normal; occasionally 150 could be normal.
What's all this got to do with the PCV?
With a V8 and a performance cam, IMO, just stick anything on there, it will all come out in the setting of the bypass air.
This is also why I prefer drilling holes in the plates for bypass air, As the throttle opens, they do less and less and the PCV does more and more, until it hits its max.
Some guys have a poor opinion of drilling holes. But I have seen very powerful 2-stroke outboard marine engines from about every manufacturer you can name, and every one had holes in the throttles. You know how those engines idle? with fully closed throttles, and variable timing, sucking thru those little (sometimes not so little) holes in the blades.
But; So what? you say.
Hey, it's HotRodding; we do what needs to be done, usually in the simplest and easiest way possible.