Ben Diss

Got of picture of all that?

Ben Diss

I guess what I'm missing in all this, is why it's important to provide vacuum to the valley cover and valve cover tubes? Why is vacuum needed in the crank case?

AintQik

Its supposed to help the rings seat but I have seen no blow by or oil usage with valley pan capped off. I know its is supposed to have vacuum but I don't like ingesting oil.

Mike, on the 4 or so cars I've seen the cans were catching oil. Just an ounce or so. My car is driven hard but the others were daily drivers. Bone stock they eat oil.

haljensen

You don't need vacuum in the crankcase, you need neutral pressure. Thats why there are 2 air feeds to the crankcase. The line from the valley cover to after the TB is vacuum to remove blow by and to satisfy Emission regulations by routing the blowby to the combustion chamber, the line from the valve cover to before the TB is for "make up" air in case the intake vacuum creates negative pressure in the crankcase.

In an ideal situation you wouldn't need to vent the crankcase but ALL motors leak combustion gases past the rings into the crankcase. Before Emmision Laws motors just used breathers to relieve blowby. Now we have Positve Crankcase Ventilation (PCV) using intake vacuum to route the blowby into the cylinders to burn it instead of just dumping it into the atmosphere.

With the crankcase pressurized either positive from blowby or negative from intake vacuum there's resistance to the piston movement. Resistance of piston movement is not good, it causes loss of usable power.

Ben Diss

Thanks!

PeterM

This is fact, as I'd noticed oil in the throttlebody while installing the Vararam (300 miles on the car).

TTRotary

I can take pics when I'm back in town friday, if someone will host them.

TTRotary

Just to clarify the whole vacuum issue...our cars normally do not run crank vacuum at all, as Haljensen has pointed out. Air is pulled through the motor by intake vacuum, but it always flows.

Racers and engine builders, however, like to run case vacuum, because it pulls the rings tight against the cylinder walls, producing better sealing and therefore more power. It also reduces blow-by, an especialy serious issue on FI cars, and especially for the LS engines, which use low-tnesion rings for reduced friction and fuel economy.

Cool, just cap off or restrict your crank intake to produce some crank vacuum, right? Not quite. While this setup works fine while the engine is in part-throttle, your case vacuum will disappear by the time you want it most, at WOT, because the intake is not longer generating vacuum. So, while running some vacuum on a Corvette may provide fuel economy benefits at part throttle, it will not do anything to improve power at WOT. Also, the vacuum neeeds to be mild, as the various engine seals were not designed for excessive pressure or vacuum.

Race engines solve the problem by simply running a vacuum pump, so they have crank vacuum all the time. Lack of crank ventilation and oil contamination is not a concern since oil is changed frequently, after every race.

I'd be curious to know what setup the C5Rs run.

Bruno0825

Cartek can works and looks great!

Ben Diss

I can host them for you. PM me when ready.

TTRotary

Will do. You'll hear from me tomorrow eve. Thanks.