1991sleeper

iTrader: (-3)

OK ... I know sometimes ppl go through alot of trouble to pull vacuum on the crankcase such as : header evacuators , vacuum pumps , pcv systems etc ... but I really don't have a lot of knowledge about this and would like to educate myself on the subject ..

But first I have a specific question ... I'm still running the factory pcv system and was thinking ... if I plug the passenger side valve cover and leave the pcv system in the drivers side would this not work quite well similar to a vacuum pump ? And help seal the rings a little better possibly ? Thanks !

Also Feel free to discuss the topic to full extent !

AlkyIROC

The PCV system does help with keeping the crankcase at a lower pressure however it's not the same as a proper evac system.

It's not just pressure or ring sealing. There's condensation (water) plus containments in the crankcase vapors. The PVC system sucks that junk and feeds it back into the cylinders to be burnt and set out the tailpipe. Water doesn't burn. Excessive oil vapor isn't good in the combustion chamber either.

With a header evac system, it's about as efficient as a PVC system except it's dumped directly into the exhaust. At the most, they'll only pull 2-3" of vaccum. Electric vaccum pumps work at low rpm and idle speeds but can't pull enough vaccum at WOT.

Belt driven pumps are the best for pulling a crankcase into a vaccum. If too efficient, a relief valve needs to be used to limit how much of a vaccum the pump will pull. Pulling lower than 12 inches can pull oil from the bearings and wrist pins.

If you have too much crankcase pressure then you have too much blowby past the rings. A proper fix is a rebuild. A good cylinder leakdown test should be in the 2-5% range.

sofakingdom

iTrader: (1)

The reason people use mechanical pumps of whatever sort on race cars, is because, at WOT, THERE IS NO VACUUM. PCV does nothing whatsoever.

For a street car,,, ... ,,, .. whole different matter.

That's one of those things that just because "all the fast cars do it", doesn't always make sense for the rest of us.

If you run your 305 TBI car on the street, the factory PCV setup works JUST FINE as it is. Use it to your advantage. There's nothing to be gained by blocking the system's make-up air intake.

FRMULA88

Everything you wanted to know about the PCV system:


http://en.wikipedia.org/wiki/Crankcase_ventilation_system

FRMULA88

Everything you wanted to learn about crankcase evac systems.

An overview of Passive systems & Vacuum pumps systems

http://www.enginelabs.com/engine-tec...up-horsepower/


Welcome to Hot Rodding ! Hope you enjoy reading !

FRMULA88

Vacuum Pump Advantages




Pulling vacuum with a dedicated pump has been the preferred method for well over two decades now and the technology has steadily advanced with important performance benefits that include:
•Improved ring seal by relieving crankcase pressure below the rings
•Reduced friction by allowing lighter tension rings
•Reduced windage around the rotating assembly
•Improved oil scavenging
•Reduced parasitic pumping losses
• Minimized cavitation (in wet sump applications)
•Reduced lubricant contamination
•Improved bay to bay breathing in Y-block configurations
•Improved power via reduced mixture contamination
•Reduced gas port contamination

1991sleeper

iTrader: (-3)

Cool man ! Good read