I had tunned this carb (390) without the PCV hooked up and it ran fine. I have now drill and tapped the manifold and hooked it up. The engine is running alot leaner at idle and is tring to stall for time to time. I have pinched the hose off for now untill I get some more time to really tune the idle correctly.
Is there any real benifit to having it hooked up? Fuel mileage, power, enviroment, keeping the oil from blowing out the seals?
I have a crank case breather which should keep the pressure down.
http://tinyurl.com/3xj66k

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

The breather does two things.

When the crankcase is pressurized it allows crankcase gasses to be vented. (WOT)

When the crank case is in a vaccume the breather allows fresh air in.

The PCV valve allows a metered amount of crankcase gasses to be pulled from the crankcase at most vacume levels (not WOT)

Not running a PCV causes sludge and nasty buildup.

Before PCV was the Road Draft system where the gasess were pulled out by hanging a tube under the car. ....the breather supplied fresh air...

The crsankcase fumes were so nasty for the environment that the first thing they did to control pollution was to burn them in the motor.

Our mudbogger has no vaccume.....so we use a header valve thingy that pulls the fumes into the header by exhaust pulses....it wont work with a muffler. It still uses a breather. It would work with a cutout.


What you actually need to do is just richen your idle mix .......

The PCV lowers your vaccume signal at an idle.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

PCV is all benefit, zero drawback. See this thread. You just need to make sure you're using a suitable PCV valve in good condition, make sure you haven't created any new vacuum leaks, and re-adjust the engine idle mixture and speed.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

In my experience, you have to richen things a little bit if you're using a good PCV system. Car runs better and overall drivability improves a lot. Also I would love to get input on the A/F ratios... I would tend to guess they would even up a little better than with no crankcase vent at all.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

I haven't messed with it yet, but the AFR was 12.0 at idle and now with the PCV hooked up it idles around 14.0 14.7.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir