Pcv routing and pressure

[chappys4life]

Struggling with pcv routing on my 1978 k5 blazer with a 350. I swapped the stock quadrajet to a quick fuel brawler which is Holley 4150/4160 style.

I routed the pcv valve from the driver side valve cover to the back of the carb. Got a fitting for the stock intake to brake booster. The passenger side valve cover is vented to the air now, new air cleaner (summit air cleaner) is on the way as the stock doesn’t fit. When I turn off the truck I get a high pressure hiss from the brake booster? Not sure how I should re-route it. Happy to get new valve covers or change the routing/vents on factory valve covers.

 

[Bent77]

The base of the carb and the port on the upper runner of the intake provide the same vacuum. Does the booster hiss when the PCV port in the carb is plugged? Will be safe to test with the the other valve cover already vented

 

[Joel Wilson]

Usually there is a hardline that goes to the base of the carb or the intake and then a rubber hose that goes to the check valve on the booster. Is the rubber hose in good shape? I've also had to replace that check valve before on my 76 cause it was leaking.

Joel
norcal

 

[Wes Harden]

Check valve at booster and or grommet

 

[chappys4life]

The base of the carb and the port on the upper runner of the intake provide the same vacuum. Does the booster hiss when the PCV port in the carb is plugged? Will be safe to test with the the other valve cover already vented

will try and see

Usually there is a hardline that goes to the base of the carb or the intake and then a rubber hose that goes to the check valve on the booster. Is the rubber hose in good shape? I've also had to replace that check valve before on my 76 cause it was leaking.
norcal

on my 78 the brake booster was connected by rubber hose to the quadrajet . The replacement Holley doesn’t have a 2nd port to use. The hose is brand new from intake fitting to brake booster.

 

[Bent77]

will try and see



on my 78 the brake booster was connected by rubber hose to the quadrajet . The replacement Holley doesn’t have a 2nd port to use. The hose is brand new from intake fitting to brake booster.

Is there a check valve between the engine and the booster as Joel and Wes mentioned? If so, maybe it’s been reinstalled backwards

 

[diesel4me]

The check valve only goes in one way..one end had a bigger barb fitting to plug into the booster's grommet,and the other end has a 3/8" hose barb fitting...if replacing the check valve fails to stop the hiss,then the booster itself probably has a ruptured diaphagrm.

GM also put a charcoal canister in-line on later vehicles ,looks like a fuel filter,so vapors from the gas wont ruin the rubber diaphragm in the booster...the grommet,and canister filter must be air tight so as to not lose vacuum..