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I have a 72 Cutlass with a 350 4bbl quadrajet. I have been tossing around the idea of replacing the factory air cleaner assembly with an open air cleaner. Could anyone confirm to me all of the other minor details that are involved with doing this. Breather, vacuum lines, etc. Thanks, Mike
Plug the vacuum lines that would normally go to the Thermac, and put a filtered breather where the factory valve cover breather is now. You could leave the factory breather in place, but it will look stupid just sitting there.
Something similar to this. Not sure if this particular one would actually would work, but along these lines.
Example: Edelbrock 4403 Edelbrock Signature Series Valve Cover Breathers | Summit Racing
Don't bother running a tube to the bottom of the air cleaner because it will put the tube location on the low pressure side of the air filter and suck the air out of the breather instead of letting filtered air into the engine. PCV should go to the carb, so you should be fine over on that side.
Plug the vacuum lines that would normally go to the Thermac, and put a filtered breather where the factory valve cover breather is now. You could leave the factory breather in place, but it will look stupid just sitting there.
Something similar to this. Not sure if this particular one would actually would work, but along these lines.
Example: Edelbrock 4403 Edelbrock Signature Series Valve Cover Breathers | Summit Racing
Don't bother running a tube to the bottom of the air cleaner because it will put the tube location on the low pressure side of the air filter and suck the air out of the breather instead of letting filtered air into the engine. PCV should go to the carb, so you should be fine over on that side.
Thanks for the reply. This is exactly what I had thought but wanted to make sure that I didn't forget anything.
Just make sure the base on the new air cleaner clears all linkages and any hood clearance issues are checked. If everything else is stock, you probably won't see much in the clearance issue department. It's kinda mundane to have to check it all, but I've seen where the first time a throttle was opened with an aftermarket air cleaner and it got stuck wide open under the air cleaner base somehow. Not good. It was a 68 Camaro big block. Wasn't mine. Scary situation.
Just get a 4" tall filter element. This opens up about a 5/8" gap between the body and the lid of the air cleaner housing all along its circumference and you get free airflow without having to replumb or reroute anything, plus you retain factory appearance. Win-win.
Just get a 4" tall filter element. This opens up about a 5/8" gap between the body and the lid of the air cleaner housing all along its circumference and you get free airflow without having to replumb or reroute anything, plus you retain factory appearance. Win-win.
Or turn the lid over, like we used to do w/ Dad's car to hear the roar of the Quadrajet!
I recall seeing vintage footage of Oldsmobile employees running a car at the test track and they flip the air cleaner lid upside down. Of course, if you just want the aftermarket appearance make sure you keep all the OE parts so you or a future owner can go back to stock
Nearly every aftermarket open element air cleaner has a knockout on the underside for the vent hose fitting. Most people ignore it, but it's a good idea to reconnect it. You can also buy the fitting separately.
Thank you all for the replies. I have seen and can remember multiple lids turned upside down lol.
Joe, I actually just picked up an air cleaner from Summit today and I did in fact see the knockout for the vent hose when I opened it up. I will look into the fitting replacement.
The base will not seat, it is touching a "high spot" on the choke side. It's all good. I'm not one to chase multiple aftermarket parts until they fit. It's more upsetting when the description states it will fit and then it doesn't. I guess if there's anyone out there that has a link to one that they have used and is known to fit I'd give it a whirl. I don't mind the stock look at all, was just thinking of changing it up a bit.
Guess I could always just buy a spacer. It only needs about 1/4 inch.
Last edited by 72 Post; March 6th, 2023 at 06:16 PM.
Reason: additional comments
The base will not seat, it is touching a "high spot" on the choke side. It's all good. I'm not one to chase multiple aftermarket parts until they fit. It's more upsetting when the description states it will fit and then it doesn't. I guess if there's anyone out there that has a link to one that they have used and is known to fit I'd give it a whirl. I don't mind the stock look at all, was just thinking of changing it up a bit.
Guess I could always just buy a spacer. It only needs about 1/4 inch.
These aftermarket open element air cleaners are all designed to clear Holley carbs, and maybe E-brock carbs. A spacer is the easy solution.
Don't bother running a tube to the bottom of the air cleaner because it will put the tube location on the low pressure side of the air filter and suck the air out of the breather instead of letting filtered air into the engine.
This is a good thing if the engine has above normal blowby.
Don't bother running a tube to the bottom of the air cleaner because it will put the tube location on the low pressure side of the air filter and suck the air out of the breather instead of letting filtered air into the engine. PCV should go to the carb, so you should be fine over on that side.
This is not correct. The pressure above the throttle plates is still higher than pressure below the throttle plates - otherwise gasoline would flow OUT of the engine instead of into it. Since the PCV valve is connected below the throttle plates, that will be lower pressure that at the vent tube, even when connected under the air cleaner.
My car came w/ this air cleaner when purchased. 1971 350 w/ 4 bbl. It has a 1 1/4" spacer on the carburetor between the Air Cleaner & top of the carb. Works great. Tube from the left side valve cover runs to the bottom fitting of the air cleaner. I have the original air cleaner also, but this one seems to work well now that the choke is adjusted properly.
Last edited by Falkon; March 7th, 2023 at 11:47 AM.
This is not correct. The pressure above the throttle plates is still higher than pressure below the throttle plates - otherwise gasoline would flow OUT of the engine instead of into it. Since the PCV valve is connected below the throttle plates, that will be lower pressure that at the vent tube, even when connected under the air cleaner.
Thanks for the correction. After thinking about it, yes, it's beneficial to have it route to the air cleaner, although not required. But I wouldn't do it for emissions reasons becuase who really GAF on a 50 year old system where tailpipe emissions far outweigh any oil vapor escaping from the engine compartment. The bonus in doing it is that any oil vapors end up inside the engine vs. all over your valve cover using those mesh filled deals. Look at some of the Chevies that came with the open air cleaner from the factory with the tube jammed into the valve cover. They had a big *** metal tube pre-attached to the air cleaner base. They seemed to do ok.
March 5th, 2023, 05:44 PM
