Technical You guys have an answer?

I picked up a small block chevy the other day. It has a performer aluminum manifold on it, when I pulled the carb off and looked over the manifold it had two 3/8th inch holes drilled into it under the carb into the oil valley area. Would this be done to reduce the vacuum pressure in the engine?
John

 

Possible homemade pcv system. Vacuum pressure "lives" in the intake passages, not in the crankcase.

 

You sure those holes go all the way to the crankcase? I've seen something similar but it went into the exhaust crossover as part of the EGR.

 

Is vacuum pressure equivalent to suck blow?

As stated this might be an attempt at a pcv system, but a rather piss poor one in that it has no regulation (other than the hole size) and no oil separation from the fumes.

Plug the holes and install a proper system.

 

Edelbrock 3706 Performer EGR:

http://www.ebay.com/itm/Chevy-GMC-3...Parts_Accessories&hash=item2338fea083&vxp=mtr

 

That's weird. EGR with no EGR valve? How can this be?

 

They apear to be cast into the manifold rather than drilled and they don't go all the way to the oil valley. I guess they are factory holes.

 

The passage from the head is blocked at the pad where the EGR valve mounts. EGR valve sits beside the carb and meters the exhaust to those two holes.

 

I have never seen that before!! Maybe edelbrock could give you a answer, or shed some light on these holes?

 

This sounds like a good answer...Thanks

 

Learn something new every day. Unless you need EGR to pass emissions I'd still block 'em.

 

"50 state street legal means more sales"

 

had to have them on post 76 cars here in Illinois if they pulled a visual exam ( which was rare but it has happened in the past) . we ussually plated the egr over after testing and reset the timing back .

 

Maybe hidden nitrous injection

 

I was thinking a hidden nitrous system as well.

 

Just what is "vacuum pressure"? Vacuum is the absence of pressure.

 

vacuum pressure would be suction.

 

Vacuum is negative pressure, but pressure nonetheless.



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'Blow' is only an expression...(!)

...And AMEN to a non-regulated re-circulatory moving of C/O. Positive Crankcase Ventilation was always regulated through a valve!

 

Got the same holes in my SBO intake…I welded up the EGR deal.

 

Vacuum is negative from 0 PSI, but it is not pressure.

 

Vacuum is any LESS pressure than the pressure being introduced to to area.

 

It depends on your reference point you use 14.7 ( atmospheric ) or absolute .

 

Vacuum has many different definitions and so does pressure.

Vacuum (used in the automotive sense) is pressure. When we say Vacuum we mean suction as in negative pressure pulling atmospheric pressure in. Saying there's no such thing as negative pressure is like saying there's no such thing as negative gravity. An astrophysicist may say there's no such thing as negative gravity, but don't tell that to an aeronautical engineer or the designer of a rollercoaster.

Absence of pressure is equilibrium. No suck, no blow. No pressure, no vacuum. You can't say that a strong vacuum is a big absence of pressure.

 

Ah no the higher pressure is pushing itself into the area of low pressure there is no suck.