PCV valve for road draft tube block SBC

GM did not use a road draft tube or later a PCV system for looks! It's there to prevent moisture from condensing inside the engine and creating sludge, fresh air must be pulled THROUGH the engine...fresh air in and moist air out through either system. Simple breathers won't do that. There is more than one way to do it but always think about where the fresh air enters the engine and where it exits the engine. The most important part to remember is that there must be air flow through the motor.

 

Why is it better to have the intake on the air cleaner vs. the tube breather?

 

I'm ditching the road draft on my 283 as well. I have vented valve covers without any other holes for a fill cap or breather. I have an oil fill tube on the intake (an old Edelbrock TM-1). Do I need a vented or sealed cap? What do I need to complete the pcv conversion? I do not want to drill the valve covers (they are vintage) but I can seal off the vents from the inside if I need to just retain them for looks. I also have a threaded port just below the carb on the back of the pedestal. Can one of you pcv experts lay a system out for me? Sorry for the hijack but I didn't want to start a whole new thread.

 

From the road draft port on the block, install a PCV in the vertical position. Run a hose from the PCV to the intake manifold plenum, or carb base (air flows from the road draft tube to the intake plenum which is under vacuum). Install a vented and filtered breather on your oil fill tube to replenish the air. As long as your engine has the baffled canister in the pushrod valley, you are g-2-g. If not, you'll need a different setup to prevent oil suckage into the intake manifold.

 

Roger! Is the oil tube breather enough that I can seal off the vent pedestals on the valve covers? They made a bit of a mess when the road draft tube was installed.

 

Great thread, I have a early sbc with that filler tube up front. This will be very helpful.

 

Yeah this is a really good thread. So was the RDT phased out after '67? I'm rebuilding a 1968 327 that has sealed valve covers and just a vented oil fill tube for crankcase venting. Where the RDT is located in those pictures, its just decked flat with no hole in the block.

 

I'm happy to report, the parts listed in post #12 are still available @ O'Reilly's.
I picked up part# 42323 (grommet), part # PCV181 (valve), part# S602 (hose barb) for the rear carb base port & a length of hose for $10 yesterday. Removed the road draft tube & installed this in a matter of minutes ('65 283). Fits perfectly.

I have a front fill tube w/ breather that's been spitting oil on the windshield...hopefully this will be a bandaid until it gets rebuilt this winter.

 

Hi guys I have a later 350 with no RDT hole & im running a edelbrock c26 manifold with filler in the front & corvette no hole valve covers . how do I run a pcv valve? i have issues at open road speeds 60mph with oil drops on the screen its a real pain

 

I couldn't keep oil off my windshield no mater what I did. Pcv in the back breathers in the valve covers. Nothing until I made a little shield for the front breather like the ones on an 8ba only backwards. The air running under the front breather creates a vacuum or just blows the droplets off it. Doubt the zips helps. I don't think the Pcv works at speed.


Posted using the Full Custom H.A.M.B. App!

 

I'm running the newer 350 with no RDT hole. I was gonna run the PVC in the oil fill tube in the front of the intake. With a sealed cap. Am I missing anything? (I got no hole valve covers so I can't vent from them.)
-Pat

 

you need a vent to get the fresh air in. The vacuum at the carb base would be pulling the air through the pcv from the fill tube...but where will that air be circulating from?

 

HI guys I just redid my 84 Firebird which has a Chevy 350 in it and i only went with one breather no pcv or road tube. I made a road tube off the valve cover but what angle to i make the end that faces the road. I heard they where suppose to be a specific angle to get the suction.
Thanks

 

Sorry I made that really unclear. My breather i had put on was blowing oil all over my valve covers so I was told I needed either a PVC or road draft tube. I ran a hose down off the valve covers but I just wanted to know if there's anything specific I have to do to it to get the suction affect from the road. I was told I should also put a breather on the opposite side of the road draft tube is that true?

 

The bottom of the tube should be at 45 degrees on the back( shielded on the front). This creates a low pressure behind as the road wind passes by drawing out the fumes/gasses etc. What most are missing here is that the carb will be metered for the flow from a PCV system and not just plugged. Its a very simple system and this has been covered many, many time on here( I know this is an old thread) . If you have a PCV valve you MUST have fresh air flow for it to work. JW

 

Ok thanks yah I have a breather oil cap now to allow the flow in and the road tube mounted to a breather with a baffle over cylinder 1 running under the car. I'm going to mount the end soon should I have it hanging just under the lowest point of the car? Or does it not matter?

 

It should be low enough to get direct road wind, level with the bottom of the pan will do. JW