[78transam]

Hello. I was wondering what the hole is in the back of the intake manifold on my 231 v6 firebird. Please see pictures attached.

Fumes pour out of this hole when the engine is running.

Currently I have a PCV valve in the passenger side rocker cover, and a breather in the other rocker cover. This PCV setup has very little effect on the fumes from the hole.

Thank you.

[sbchevfreak]

How does it run? That looks to go directly into an intake runner, and should be a huge vacuum leak. If fumes are coming out of it, I think something else is also wrong, but I'd try plugging it ( it looks like it's threaded ) and see what happens.

[78transam]

There is a rubber grommet in the hole, but the PCV valve doesn’t fit it. The fumes have an exhaust / burning oil smell.

I am not sure if there is a lifter valley cover plate, like there is on the V8 or if this manifold seals on the lifter valley instead of a cover plate. This is another thing that has puzzled me with this engine.

[olsixrod]

That hole is for the power brake booster vacuum line, its a 3/8 ths aluminum hard line. If you've got smoke coming out, check the EGR valve, it's probly stuck open or carbon clogged RED

[78transam]

I have the EGR blanked off, and I just checked the power brakes, they seem to be connect to another fitting on the manifold.

I have only had the car for a year, it has never run properly since I've had it (stalling, bad miss-fire, hesitation, lack of power). Perhaps this could be the reason why?

[DoubleVision]

From what I can tell it`s a direct manifold source vacuum, it`s there usually to run the modulator valve on a automatic transmission. the "smoke" you see coming out is the air fuel mixture that comes to a sudden stop when the valve closes on that runner. It`s no wonder it`s never run right, get it plugged off and it`ll likely run better, if it hasn`t done damage yet from the engine running too lean.

[1ownerT]

I have had a couple of early 80's 231's that used that hole for the PCV, yours may be different.? The two were untouched OE's. You state that the PCV does not fit, is it the correct one listed for that engine.? The valve is a tight fit and they have been known to push the grommet into the lifter valley, the intake gasket has a pan so the grommet does not fall all the way in.

[78transam]

I can not confirm that it is the correct PCV valve for the V6. I have another from a 400V8 which is identical to the one I have in my V6.

The car has after market chrome rocker covers, and all the emissions equipment has been removed, so I don't know how much of the car is stock.

Dose any one know what the correct stock setup for the PCV system on the V6 is. Perhaps this will help me understand what I have.

Thank you for your help.

[78transam]

Update:

Thanks for the help.

I have managed to connect the PCV valve to that hole in the manifold.
I found that it did go directly to the lifter valley (there was no cover plate?).

I have an air breather on the driver side rocker cover, and now no smoke comes out of it.