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489 Lemans
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air cap

You should not replace the pcv with an air cap. The air cap replaces the white fuzzy in your breather for fresh air feed to crank case. The pcv still pulls off crank fumes and relieves a small amount of crank case pressure caused by piston ring blow by.

On open headers you can use the exhaust to create a vacuum to pull the crank fumes. This also increases hp by releiving pressure from the crank case. In this case K&N air cap is best.

On real high hp cars. You can install an air pump to pull fumes and relieve even more crank case pressure. This adds 15 to 25 hp.
 

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Before PCV valve, motors sucked air in the top (filler filter or valve cover filters) and had a pipe vent from the block out the bottem cut at an angle to pull air as you drove. So there was air flow thru the block. No PCV=no flow.

For fumes and fire safety do not remove the PCV valve

Your carb is designed operate with the CFM from the PCV valve, don't remove it and make sure you have the right size PCV valve.

Condensation forms in a motor and forms acids, the PCV sucks it out.

Street car, use the PCV, Race car was explained by brackteer
 

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red65mustang said:
Before PCV valve, motors sucked air in the top (filler filter or valve cover filters) and had a pipe vent from the block out the bottem cut at an angle to pull air as you drove. So there was air flow thru the block. No PCV=no flow.

For fumes and fire safety do not remove the PCV valve

Your carb is designed operate with the CFM from the PCV valve, don't remove it and make sure you have the right size PCV valve.

Condensation forms in a motor and forms acids, the PCV sucks it out.

Street car, use the PCV, Race car was explained by brackteer
On my 327 I just picked one that had 3/8 threaded male on the end, I did see lots to choose from but didn't know which was which. Seems to be working fine but would be intrested in the differances. Ed ke6bnl
 

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Ed,

not "critical" on most motors, just better overall performance and maybe some mpg..

main differences:
size of the inlet hole (max cfm,)
weight of the "rattle" (how much Hg to lift it)
strength of the spring (how fast/far it opens)

the PCV is opening and closing while the carb is transitioning richer/leaner.
wrong pcv= wrong air fuel mix accelerating/decelerating
 

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red65mustang said:
Before PCV valve, motors sucked air in the top (filler filter or valve cover filters) and had a pipe vent from the block out the bottem cut at an angle to pull air as you drove. So there was air flow thru the block. No PCV=no flow.

For fumes and fire safety do not remove the PCV valve

Your carb is designed operate with the CFM from the PCV valve, don't remove it and make sure you have the right size PCV valve.

Condensation forms in a motor and forms acids, the PCV sucks it out.

Street car, use the PCV, Race car was explained by brackteer
I agree. '60s cars used ahat they called a road draft tube to pull vapor out of the engine, as stated above. Take a look at what happens with no PCV or road draft tube. No negative pressure to the crankcase to get rid of the unburned gas/oil vapor.

The PCV was the ONE thing that the emission people did correctly for a street driven vehicle.

People that ask about doing away with the PCV, on a street engine, have not bothered to research how an internal combustion engine works. They should not be Hot Rodding anything, until they get the basics correct.

Just my opinion, but JFC, there are libraries that have books that explain this. But I keep seeing this same question asked on just about every SBC forum. Step away from the keyboard and try reading! (rant off)
 

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Discussion Starter · #10 ·
I ask this question because I was thinking remove pcv could make the carburator and the rest of the engine cleaner .So the best should be a PCV on one side and a air breather cap on the other. Thanks
 

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the pcv sucks air from below the carb, the dirty air doesn't go thru the carb.

Suggestion: go to the main bulletin board page, click on the "hotrodding basics" link, click on the first post by Jon, scroll down to the carb section, worth reading for sure!

Merry Xmas (from Jon) a little late, articles on "A" to "Z" for all parts of your car........
 
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