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Post Info TOPIC: can you run a sb without a breather or vent to the valve cover?


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can you run a sb without a breather or vent to the valve cover?
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Is this necessary?  I would like to run 66 valve covers that aren't designed for a breather or to be vented to the air cleaner base.  Thanks



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Jim L

Lake City



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You may than need a draft tube.

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Bruce L. - Lakeville MN

1971 Malibu Convert

1951 Pontiac Chieftain Super Deluxe Catalina Hardtop 



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I was looking at 409 and 348 intakes and valve covers and they didn't appear to have access for a vent.  suppose it was maybe in the block.  What do you mean by drafting a tube?



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Jim L

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on a 283 it was on the back of the intake and wend down towards the ground under the engine and the breather was in the front where you put the oil in

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Bruce L. - Lakeville MN

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You can drill a hole through the intake manifold if you are careful not to hit intake, exhaust, or water. Tap it for pipe threads, and run a tube or hose down the back of the block, or rig a PCV valve to a vacuum source.

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Larry L.

Coon Rapids



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To run valve covers without any venting and PCV from the fill tub, you would need an early block that has a crankcase vent in the back near the distributor. I don't recall any 350s with a vent hole in the behind the dist, back of the block, they all used valve cover venting.



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Bob W.

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Yeh Bob. Guess there should have been a hole drilled and taped in the rebuild for a possible vent

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Jim L

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jim larson wrote:

Yeh Bob. Guess there should have been a hole drilled and taped in the rebuild for a possible vent


 I don't know if that's possible with the block you have.

With Holley there is an air cleaner base with a tube for CC vent, you would have to move the PCV to the left side valve cover than connect from the right side valve cover to the air cleaner base. Search the Covette catalogs. This would pull filtered air into the CC and look more original.



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Bob W.

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I think your engine had roller rockers, they will not fit under stock valve covers without using a valve cover spacer.



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Chris P
East Central, Mn

66 Chevelle 300 deluxe



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67ss wrote:

I think your engine had roller rockers, they will not fit under stock valve covers without using a valve cover spacer.


 Yes I was also thinking of that, hadn’t thought about the valve cover spacers, thanks.

With all things considered looks like the best option is to keep the valve covers I have and run the air cleaner base breather tube to the rear valve cover hole on the pass side.  Then stick something unique in the drivers hole and run the PCV valve from oil fill tube to the carb.

Any and all ideas welcome, maybe just  another breather all else fails.



-- Edited by jim larson on Wednesday 15th of September 2021 04:09:44 PM

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Jim L

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Jim,
I know nothing about nothing.
Didn't many of the the pre-smog vehicles vent through the oil fill with the added pipe on back of intake??
Vented valve covers were added later.
The small block 66 Valve covers had no vents.
The early corvette valve covers have no vents or oil fill.
There was a vent tube on back of intake that runs down the side of the bellhousing.
Some of the oil fills even had a provision for a pvc valve.

Your L-79 intake has the provision on the back for that pipe, correct?
Cannot remember if that pipe bolts directly to block or through manifold and into block, one long bolt holds it on.

Thinking out loud.
Remember, I know nothing about nothing as stated by Sergeant Shultz the great German philosopher.headscratch

Karl



-- Edited by more ambition than brains on Wednesday 15th of September 2021 06:30:08 PM

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More ambition than brains,

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Thanks Karl for the information and added humor.  Something else for me to check.  Ron should know for sure.  If so, I could run 66 valve covers as long I use valve cover spacers for my double roller rockers. or switch back to a set of single tip rockers I have.



-- Edited by jim larson on Thursday 16th of September 2021 08:12:23 AM



-- Edited by jim larson on Thursday 16th of September 2021 08:13:33 AM

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Jim L

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The issue with adding a vent tube to the intake will be the possibility of oil escaping with the blow by. The engine blocks that originally had this system were cast to accept a canister filter under the intake to remove the oil and let it flow back into the pan. Not having that will, eventually, let oil escape and possibly mess up the function of the pcv in the intake tube, by letting it draw air from the draft tube, rather than the crankcase.

My '67 Camaro had the pcv in the filler tube at the front with no visible means of drawing in outside air. It is a closed system and requires the correct pcv valve to balance the amount of air drawn thru the valve to prevent a vacuum in the crankcase.

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Mitch D.   River Falls, WI

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1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20



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I guess I will stay with the pcv  in the valve cover, maybe just add a hose to the oil fill tube kind of do a Y  PCVs hook up to the fitting on the carb.  Then used a closed vent system to the air cleaner base if all that works.



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Jim L

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more ambition than brains wrote:

Jim,
I know nothing about nothing.
Didn't many of the the pre-smog vehicles vent through the oil fill with the added pipe on back of intake??
Vented valve covers were added later.
The small block 66 Valve covers had no vents.
The early corvette valve covers have no vents or oil fill.
There was a vent tube on back of intake that runs down the side of the bellhousing.
Some of the oil fills even had a provision for a pvc valve.

Your L-79 intake has the provision on the back for that pipe, correct?
Cannot remember if that pipe bolts directly to block or through manifold and into block, one long bolt holds it on.

Thinking out loud.
Remember, I know nothing about nothing as stated by Sergeant Shultz the great German philosopher.headscratch

Karl



-- Edited by more ambition than brains on Wednesday 15th of September 2021 06:30:08 PM


 Say Karl, I don’t see anything on the intake that looks like a provision for a vent tube unless it’s just a boss drilled in the intake to hold some kind of bracket etc.



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Jim L

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The provision for the draft tube was cast into the block behind the intake.

64048617-700-0@2x.jpg?rev=1



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Mitch D.   River Falls, WI

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1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20



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See, I know nothing, however on occasion I am almost half right, just like at home.

beers



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More ambition than brains,

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more ambition than brains wrote:

See, I know nothing, however on occasion I am almost half right, just like at home.

beers


 I was thinking it came out of the intake too, but couldn't find any pics of that, so did a search for a 1962 283 and, waa-laa it is part of the block. I knew this about 50 years ago...clonk



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Mitch D.   River Falls, WI

Charter member of the "Cars apart Club"

Some Assembly Required

1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

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