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The factory had an RPO for commercial vehicles that added PCV for vehicles that wouldn't be on the highway for the most part (making the draft tube ineffective), and an optional kit (shown in the drawing for '55). Note in the image how tall the breather is that replaces the draft tube. It was designed to avoid pulling too much oil vapor into the intake system.
But sure, it can be done. Best bet is to keep the baffling of the draft tube in place, and modify for a 6 cylinder PCV valve (occasionally one of the NOS or used factory PCV set ups show up on eBay, but they are rare at this point). The valve cover should be sealed of course, if the engine has one with the breather slots (model year dependent), and a better inlet connection designed. Note the factory mod has a tube running from air cleaner to valve cover added for that.
Hi Tim, It is a 1959 235 and has a road draft tube. I was planning to clean it today but have not got around to do it. Hope to do it tomorrow I will report back. Thanks Steve
The factory had an RPO for commercial vehicles that added PCV for vehicles that wouldn't be on the highway for the most part (making the draft tube ineffective), and an optional kit (shown in the drawing for '55). Note in the image how tall the breather is that replaces the draft tube. It was designed to avoid pulling too much oil vapor into the intake system.
But sure, it can be done. Best bet is to keep the baffling of the draft tube in place, and modify for a 6 cylinder PCV valve (occasionally one of the NOS or used factory PCV set ups show up on eBay, but they are rare at this point). The valve cover should be sealed of course, if the engine has one with the breather slots (model year dependent), and a better inlet connection designed. Note the factory mod has a tube running from air cleaner to valve cover added for that.
Hope this helps!
Drdoug . Please explain the need for the tube running from the valve cover to the air cleaner . I have a 261 with a similar pcv but not a tube to the valve cover . I do have a vented breather cap .
John
Last edited by panel fan; Tue Jun 02 2020 11:34 PM.
John, either setup will work, as long as there's a way for air to get into the valve cover. After 1968, the "Clean Air Act" in the USA mandated "closed" ventilation systems that put air from the "clean" side of the air filter into the crankcase so there was no possibility of fumes from the crankcase getting into the atmosphere. GM's PCV setup in the 1950's did it to assure no "dirty" air could enter commercial engines and promote abrasive wear. If the vented oil filler cap has some type of filter built into it, the same thing will be accomplished. Jerry
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John, Jerry covered your question nicely. Either the "clean air" routed from the air cleaner to the valve cover, or a vented filler cap with internal filter will work just fine.
