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Hi I have a 78 corvette with a 350 mildly built engine. The pcv valve is in the passenger side valve cover I know originally it was in the drivers side valve cover. My question is will it work properly in the passenger side valve cover? I could change itbut i have a demon carb with no vacuum ports on the front side. Thanks for any input
It is my understanding it is supposed to be on the drivers side due to the direction of crankshaft rotation
You have no port on the back?
Do you have a breather on the opposite side valve cover?
I think if you move it from the driver's side to the passenger side, it only works when you drive around in reverse. Sorry but we're all a little punchy from being in for the past month. Stay safe and stay healthy.
Duane
But, but, but, running in reverse doesn't run the engine backwards does it? Now woudn't that be an interesting thing to work out during the madness...
Oh no, now I've become unstable.....
From: At my Bar drinking and wrenching in Lafayette Colorado
The "best" position is with the PCV on the driver's side and the vent air coming in on the passenger side. This takes advantage of theoretical natural airflow currents in the rotating engine. But it will work just fine the other way, too. The important thing is to have the PCV on one side of the engine, hooked up to manifold vacuum, and a fresh air inlet source (which doubles as the crankcase vent system under WOT when there is no vacuum and high blowby) located on the opposite side of the engine to create a "crossflow vent" through the crankcase. Many engines, such as Pontiac, put the PCV in the lifter valley cover, so it was centrally located. As long as you have all the working parts of the system installed and hooked up, it will work great (unlike the other guy posting here recently who had his PCV connected to the air cleaner, and no crankcase vent installed in the engine...).
Thanks lars I do have a breather on the drivers side and everything is hooked up properly. the pcv valve is connected to the back of my carb to manifold vacuum its just in the passenger side valve cover because of the vacuum ports are in the back of my carb and it fits better on the drivers side. thanks again for your input i trust your opinion
Thanks lars I do have a breather on the drivers side and everything is hooked up properly. the pcv valve is connected to the back of my carb to manifold vacuum its just in the passenger side valve cover because of the vacuum ports are in the back of my carb and it fits better on the drivers side. thanks again for your input i trust your opinion
My C3 78 has the hose from the 45* nipple on the carb
correctly going to the pcv valve driver's side BUT I noticed that that hose has no vacuum ... So is that really a manifold port?
If you remove that "hose with no vacuum" and open the throttle a bit, you will then have vacuum on the line....IF it is connected to a timed/ported vacuum fitting. That is the proper place for connecting the 'signal' line between the carb and the vapor canister. If that line/fitting never has vacuum on it, there is something wrong with the carb.
The 78-79 used the 3/8" port on the throttle plate below the carburetor fuel inlet for the PCV valve.
This line also tees or Y's near the PCV valve and goes to Vapor Canister.
Near the canister this hose Y's again and serves as both the PCV connection port and the manifold vacuum port on the canister.
Back to the throttle plate, just left of the 3/8" PCV port is a smaller port that goes to the bottom port of the EGR TVS Switch.
The top port of the EGR TVS Switch then tees to both the EGR valve and is the ported (or controlled) vacuum supply to the Vapor Canister.
The 45* port on the carburetor is simply a bowl vent going to vapor canister.
Here is how I believe the 78-79 should be plumbed.
Last edited by bmotojoe; May 23, 2021 at 09:25 AM.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by gjjcvette
My C3 78 has the hose from the 45* nipple on the carb
correctly going to the pcv valve driver's side BUT I noticed that that hose has no vacuum ... So is that really a manifold port?
That's not possible, and certainly not "correct"... The 45-degree nipple coming out of the base of the carb is only 3/16" in diameter, and will not fit to the PCV 3/8" hose connection. The 45-degree nipple is ported vacuum for your EGR system, and is connected to the thermal vacuum switch on the manifold. It pulls no vacuum at idle. It also "T's" off to your EVAP system to trigger the purge valve.
pcv valve
