The Stovebolt Site Forums The Shop Area The HiPo Shop SBC PCV Air Cleaner Connection

I have a SBC that had a plastic tube connecting the air cleaner to the rocker cover as part of the PCV system. Unfortunately when removing the air cleaner recently the tube broke and in the process of removing the remains from the rocker cover grommet the grommet was also damaged (both were old and brittle).

I'm curious what others may have used to provide this rocker cover to air cleaner connection, or if people are generally using an open filter type connection at the rocker cover and eliminating the air cleaner connection.

I understand that the connections only purpose is to provide a clean air supply to the crankcase so the PCV valve connection to the intake can pull air out of the crankcase so it doesn't need to be elaborate or calibrated.

I figure that while I am replacing parts I could possibly learn from the helpful community here.

I have always tried to stay with the factory systems, normally for drivability and overall dependability it works. Depending on your machine, age of engine, induction, etc, you could use an open filter type assembly and a filtered PCV breather at the valve cover. Many late 60's and newer air cleaners had a heat stove that was thermostatically controlled and used warm air from a shroud around an exhaust manifold. That system offered improved cold weather drivability and economy. For the issue at hand, a new grommet and a push-in PCV filter would be fine.

Sounds like your PCV hose into the air filter is a ‘70’s pollution device; it routes oily air from rocker box into the air filter to be re-burned by the engine. Should be able to find a replacement at most auto parts stores. It would help if you knew what vehicle the engine came from originally to narrow down the part.

I have used a rubber grommet which fits in the hole in the valve cover and inserted a piece of rubber hose which was a snug fit in the grommet and ran the other end to the air cleaner.

The "HELP" section at just about any FLAPS (Friendly Local Auto Parts Store) should have a direct replacement grommet and elbow for one valve cover, and a similar grommet for the opposite valve cover for a PCV valve. The concept is to introduce air from the "clean" side of the air filter into one valve cover, draw it through the crankcase, and vacuum up crankcase vapors through the PCV into the intake manifold and burn them. PCV systems have been around since at least the mid-1950s in some form or another to prevent blowby and other crankcase vapors from venting into the atmosphere. As usual, Commiefornia was the first place PCV was mandated for all vehicles. At the shop I owned there in the mid-1970s, we retro-fitted hundreds of older vehicles for "closed-loop" crankcase ventilation.
Jerry

Rusted Nut - sorry I was not more specific about the engine, it started as a 1991 350 and has the center bolt rocker covers but an aftermarket air cleaner. The previous plastic tube was (I belleive) from the original engine configuration using the original grommet in the rocker cover and a corresponding grommet in the air cleaner base. I looked at my local FLAPS and can get a rocker cover grommet but didn't obtain it pending a decision on what would mate with it, the tube is not a FLAPS type part. I think the flow is oppostive of what you described and more accurately as described by Hotrod Lincoln.

52Carl - I assume that the hose needs to be reinforced or molded so that it doesn't kink and large enough ID that it isn't a restriction. The previous plastic tube was pretty thin wall but I don't think it needs to be that large to avoid restriction given the relatively low volume of air moving through the system.

When the factory switched from rubber to plastic it didn't change the plumbing theory or design. If you can't find the plastic pipe, you might be able to fabricate the part out of soft copper tube or solder an elbow.

You might try getting a piece of braided stainless hose in an appropriate diameter, and using a hose clamp to connect to the various end pieces. A lot of that style hose can be bent without kinking.

Many things you can do here. Double sided hose nipple that fits in the grommet, vacuum hose to the air cleaner. Hose nipple to your favorite type of thread, NPT, JIC, Inverted flare, inserted in to the grommet then connect to the air cleaner, etc.

Mine have a right angle fitting that snug fits the grommet on the valve cover.

Thank you all for your input. I have determined the rocker cover grommet hole is 1.0" so the grommet and breather systems I have found that require a 1.25 hole in the rocker cover will not work. I will probably install a new rocker cover gromment similar to the original and determine what hose/tube I can find that will fit in place of the formed plastic tube.

Guitplayer - my PCV valve is similar to yours but I am working on the opposite side of the system where fresh air enters the crankcase on the opposite rocker cover.

I think the drivers side has more air flow at idle. Not sure. pretty sure.
If you have dual exhaust, you can put your hand in front of the dump and feel the air difference from L to R.