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Old 04-04-2008, 06:00 PM   #1
jtranger
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Default '65 365 Pcv Valve Connection

I bought my '65 with an aftermarket carb and there is a Pcv valve and grommet where the crankcase vent tube would go. The hose with the pcv then goes to the inlet of the carb pcv connection. It seems like the carb inlet pcv is sucking in some oil into the carb. Is this pcv connection to the vent tube area ok? Thanks Larry
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Old 04-04-2008, 07:24 PM   #2
62Jeff
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Here's what it looks like on my 65, carb sucks air from the oil filler tube.

http://forums.corvetteforum.com/show...74&postcount=7
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Old 04-04-2008, 08:37 PM   #3
LB66383
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Do you also have a vent tube from the air cleaner to a valve cover, or something similar in configuration? A complete crankcase ventilation system requires both a PCV valve and a vent.
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Old 04-04-2008, 10:04 PM   #4
jtranger
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It is vented right now off of the oil filler tube. I put some filter material in the pipe off of the fitting on the oil tube.
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Old 04-05-2008, 06:47 AM   #5
Mr D.
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Quote:
Originally Posted by LB66383 View Post
Do you also have a vent tube from the air cleaner to a valve cover, or something similar in configuration? A complete crankcase ventilation system requires both a PCV valve and a vent.
The 1965 327 PCV system did not use a PCV valve.
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Old 04-05-2008, 07:10 AM   #6
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The fitting on the carb has a very small hole where the hose connects to it. This small hole regulates the volume of air passing through to the motor (no PVC). The wrong fitting, one with a large hole could very well be sucking oil from the intake to the carb. Check Paragon or other Corvette parts supplier, they have the correct fitting for your car.
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Old 04-05-2008, 07:44 AM   #7
MikeM
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There is supposed to be an oil separator under the intake which would be just downstream from your PCV. Maybe it's missing and letting liquid go through the valve instead of vapor.

It may be possible that you have the wrongly calibrated valve for your engine tune. It may be that it's not feasible to have the valve that close to the liquid oil splash. Don't know.

The safe way out would be to duplicate a factory system. Some had the PCV, some had the restrictor as mentioned. Either should work if you have all the right components in the right places.

A picture of what you have would be benificial to help you figure out what to do.
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Old 04-05-2008, 10:01 AM   #8
65tripleblack
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Quote:
Originally Posted by jtranger View Post
I bought my '65 with an aftermarket carb and there is a Pcv valve and grommet where the crankcase vent tube would go. The hose with the pcv then goes to the inlet of the carb pcv connection. It seems like the carb inlet pcv is sucking in some oil into the carb. Is this pcv connection to the vent tube area ok? Thanks Larry

The current direction of flow is directly opposite of what it should be!

Are you using the correct, stock air cleaner? The filtered, intake air to the crankcase runs from the air cleaner housing (equipped with steel screen flame arrestor), to the rear of the block (where your PCV valve is now located). Inside the lifer valley, and upstream of the air inlet, is the vapor separator cannister (which sometimes is omitted by dimwitted engine builders). Crankcase vapors are sucked into the carburetor through a special 90 degree fitting on the left side of the carburetor (pictured by poster, above). This fitting has a .090" orifice, which served as the PCV valve for 1964-65. A hose runs from this fitting, to the oil fill tube.

Flow during most driving conditions (low to moderate manifold vacuum) travels from the air cleaner, into the crankcase, out the crankcase thru the oil fill tube, into the carb orifice,into the intake manifold, where its burned. During transient periods of high manifold vacuum (i.e closed throttle operation), this flow reverses.

Your engine can be upgraded to use a PCV valve in place of the .090" orifice for better operation, but if you do so, you must use a PCV closely matched to the correct orifice size. I plan on doing this to my 327/365, but have not researched the issue, yet, so cannot offer any advice on proper PCV to use. I would strongly suggest that you use the orifice fitting (widely available, as mentioned) before experimenting with PCV valves.

Joe

Last edited by 65tripleblack; 04-05-2008 at 10:04 AM.
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Old 04-05-2008, 01:58 PM   #9
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You need the rear crankcase vent tube that connects to the elbow on the bottom of the air cleaner for the "intake" side of the system. For the "exhaust" side, since you don't have the 2818 carb with the restrictor fitting the car had originally, you can do either of two things:

1) Run a 3/8" hose with an in-line PCV valve from the nipple on the oil fill tube to the PCV port on the carb base, or

2) Use a '66-'67 oil fill tube with the threaded bung, the screw-in PCV valve, and hose to the PCV port on the carb base; same arrangement as a stock '66-'67.
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Old 04-05-2008, 01:58 PM
 
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