Too much vacuum

[hiflyr]

I am stumped my dads new crate motor 351 is producing over 200” of vacuum and you can actually hear a whistling after you shut it off. I removed the pvc valve no change checked for restrictions in the carburetor and choke etc removed the cleaner also no change. It’s effecting they brake booster.
Any ideas?
Thanks

[dontlifttoshift]

Two Hundred (!) inches of vacuum? At that number you don't have a crate engine, you have a black hole.

If you actually meant 20", that is not too high and is not the cause of your whistle.

[hiflyr]

It pegs this gauge to the end of the red. Like I said very strange and you can hear the engine still sucking “ equalizing” pressure for about 2 seconds after you shut it off!

[dontlifttoshift]

I bet it does. There are 25.4 mm in 1 inch.

What is the brake booster doing?

[hiflyr]

Just noticed the gauge is mm of vacuum “head slap”

[dontlifttoshift]

Is the check valve in the booster any good? That would allow vacuum back into the intake after shutting off the engine.

[hiflyr]

Pedal goes down after pressing it a few times and then starting engine. Pedal feels good at first then goes hard. Going to replace the fuel line hose with brake booster hose and check the check valve. IfInhit my head on this 41 Ford hood anymore today I might loose it!!!

[sccacuda]

Two Hundred (!) inches of vacuum? At that number you don't have a crate engine, you have a black hole.

Definitely going to be my favorite quote this week.

[GoodysGotaCuda]

Just noticed the gauge is mm of vacuum “head slap”

d'oh

[David Pozzi]

My daughter had a 302 Bronco. Could hear vacuum bleed down after shutting off. It had that bent over EFI intake. I think it has a lot of plenum capacity to store vacuum.