my 69 stock 350 engine has a av788 pcv. is this one right for my car?
or what do I need? didn't want to complicate things with low vac thread.
thanks.

I would go to rockauto.com , pick a similar engine and use that pcv valve.

Test your PCV at operating temp at idle. Duct tape the pass side hole and insert a vacuum gauge in the oil dipstick tube using a straight spark plug boot. Normal crankcase vacuum with a good operating PVC will give you 1-3". Mine was 6" with my stock 70 Z28 PCV. I ended up buying the hallowed out one with the small hole, thus reducing my oil consumption.
GM had many cars/trucks that consumed lots of oil so they sold GM 12572717 PCV valve, which is no longer available. I bought one at an auto store.

Use the years of R&D of the GM engineers then extrapolate. Measure your vacuum at idle then use that number to match a similar reading from stock engines from back in the day.

18hg,..use the PCV used on a 69 L-48 (300hp SS-350 Camaro for instance)
16hg,..that's about what a L-34 396 produced or a L-46 350 (Corvette)
14hg,..that's about what the 302/Z-28 produced at idle or a L-78 in 1969

Good luck!

Saw the Autozone 1009dl pcv yesterday on their wall . Did appear to be just an empty can with a small hole in the bottom as someone stated.

You missed the readings of modern cams some of us are running with. Mine is 10" at idle which is why I went with the fixed orifice.

Did the 302 Z and 396/375 hp have that much vacuum at idle ?

I always figured they were down closer to 10".

Well the 69 and 70 Z28 used the same PCV but with my roller LT1 build I don't have a stock motor so I have to use the hallowed PCV valve.

Take it off the wall and shake it. It should rattle.
As I recall a PCV valve is just a little can with a hole on the top and bottom containing a ball that plugs the upper hole when there's vacuum.
No rattle (on a used PCV valve) means goo has glued the ball down. Soak in carb cleaner til goo gone...
This doesn't address the which is correct, just BS about the operation

You could shake the $hit out of an "Autozone 1009dl" and it won't "rattle"
You have the "BS" part right though ...

I don't see what people don't get about "Fixed Orifice" (you know - a 'Hole'...) PCV 'Valves' ...

I guess I'm talking about OEM style.
When these engines were built, the PCV valves were as I describe.
I searched the thread for "Fixed Orifice" and the only A-hole I found was...
Why capitalize fixed and orifice BTW? Are they names? Proper nouns? Nope; just random words then shouldn't be capitalized.

Just to refresh ... you're original quote;
NO OEM PCV valve contains "a ball" 'that plugs a hole ( "a" ... "hole" - two [2] words ... not a description of someone you distain ... unless, of course, the shoe fits ) - period.
The internals are;
*Pintle
*Seat
*Spring - calibrated to engine requirements ...
NO "ball" ...

As stated before, you sure have the "BS" (and why is that in CAPS ) part of the design down-pat
Folks talking out their Azz ('thing' - so it's Cap'ed ) is what we see a lot of on here sometimes, and try to correct it before it becomes Internet History (Microsoft Caps it - so I will to ...) and others begin to think it's true.

Carry on ...

Today I picked up a PVC1009dl valve from auto zone with the small hole for $ 2.98.
It is a " Duralast " pt # . This is for info only.

If the idle vaccuum is way too high, maybe the idle advance is also... and if the idle vaccuum is too low, then maybe the idle advance is too low..

and/or the secondary butterflies have nor been set correct
one needs to dial in the idle carb and dizzy circuits correctly to establish the tuning specs....then go from there as described in posts above.

Not doing so, and then trying to sort PVC is like sticking ones finer in a hole in the dyke rather than fixing the issue.
The base factory PVCs as descibed above will suit any street engine.. if dialled in right.

Also it is very rare an old PVC is broken or faulty, unless someone has bashed it with a hammer or never bothered to clean it (also as described above) so the suggestion to take a visit to the local wrecking yard is also an excellent suggestion.

You need to read this.