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  #16 (permalink)  
Old 06-04-2013, 11:51 AM
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Here's some pics showing what was done to turn the valve into an adjustable orifice...



The screw is 1" long. I just drilled a hole slightly smaller than the thread diameter, and the screw made it's own threads in the plastic elbow.



Try to make the threads straight in the plastic, so that the tip of the screw comes out centered on the pcv valve's pintle.

I mounted my modified pcv valve in the top of my oil separator, away from the valvecover.

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Old 06-04-2013, 01:58 PM
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Quote:
Originally Posted by OLNOLAN View Post
It appears they are finding the correct size orifice for the engine vacuum and are no longer using a valve.
Good food for thought. The PCV valve also acts as a one way device, so if you are running forced induction, the valve keeps pressure from entering the crank case. It also serves to prevent backfire byproducts from entering the crank case as well (I would assume this would also be important to hot rodders who tend to use cams that cause a lot of reversion by more valve overlap and a late closing intake valve).
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Old 06-12-2013, 08:24 AM
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I'm adding my pcv oil results to the thread for reference:

My 383 stoker has less than 8000 miles. 9.7:1, aluminum valve covers with internal pcv baffles. Pcv is rear pass side, breather for pcv is drivers side front (at least this is how I have it connected).

I have a catch can that collects about a table spoon in 50 miles. Never measured it though, I just drain it.

If the pcv valve is correct you'll hear it almost whistle at idle (removed from the valve cover). It's sounds similar to a vacuum leak, a hiss.

My in gear idle is about 10hg vacuum or less.

I've used 3 different catch cans and had 2 that caused restricted pcv flow. They had barb connectors that were less than 1/4" openings inside and it affected my idle. I had to make my own with 3/8" ports and baffles inside and seemingly no restriction. Without some sort of baffle inside the catch can the engine will suck up some oil so the volume of oil in the catch can is lower than one with baffles.

My old stock 305 had only on foam filter in the air cleaner where the pcv connected up in to. Anyone with an oem carb intake from the 80s knows how oily that filter gets. Ideally you'd want the oil trapped and drained but oem allowed some to burn.
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Old 07-10-2013, 01:52 AM
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someone asked if a teaspoon in 50 miles was ok....

according to GM.. a quart every 500 miles is 'acceptable' oil consumption (for the older engines, not sure if this has changed with the LS-series)
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Old 07-10-2013, 04:53 PM
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Quote:
Originally Posted by kc8oye View Post
someone asked if a teaspoon in 50 miles was ok....

according to GM.. a quart every 500 miles is 'acceptable' oil consumption (for the older engines, not sure if this has changed with the LS-series)
WOW so that is 6qts of oil in a 3,000 mile drain interval? I am going to have to call BS on that (no offense).
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Old 07-11-2013, 10:45 AM
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Read the owners manual of your car. It's all there.

I'll take a look at my '98 and see if it's still there or if they changed it.
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Old 07-11-2013, 01:08 PM
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A SBC holds 5 qts, so if you go through 6 qts every 3,000 miles you'd never have to change the oil...just keep toppping it off (just like a Harley)
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Old 07-11-2013, 02:02 PM
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Quote:
Originally Posted by Silver Surfer View Post
A SBC holds 5 qts, so if you go through 6 qts every 3,000 miles you'd never have to change the oil...just keep toppping it off (just like a Harley)


I never said it made any sense!! I know of a few people that called GM to complain about what they considered 'excessive' oil consumption.. and the dealer told them the same thing.. unless it's worse than 500 miles to a quart, GM won't consider it 'a problem'

Edit: this info applies to the Gen 1/2 small blocks.. dunno at LT or LS engines... .before the LS-series engines were out.. They may have finally revised it by now..
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Old 07-31-2013, 07:39 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
That is using your noodle.
Which PCV valves have the lighter tension spring?
Is there any differences in the pindle shape? (flow)
This should be added to the Wiki.

aisr...Thanks for the great post.
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Originally Posted by Silver Surfer View Post
Wow! All this info should definitely be wiki'd!

So what is the goal of building your custom valve? Should it stay closed at idle and open up and some % of max vacuum?

I was unaware that there was a spring in the valve. My pintle opens if I turn the valve upside down.
I missed this thread when it was new. I've started a wiki, here's the first draft. Feel free to edit it.
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  #25 (permalink)  
Old 08-01-2013, 12:01 AM
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Nice work Cobalt! Thank you!
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Old 08-01-2013, 12:47 AM
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Quote:
Originally Posted by cobalt327 View Post
I missed this thread when it was new. I've started a wiki, here's the first draft. Feel free to edit it.
Beautiful!



Duke
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Old 08-02-2013, 09:58 AM
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Most auto makers use the one quart of oil per 500 miles as a benchmark, so they don't have to warranty an engine as often. It saves them money, but most of us wouldn't accept more than one quart in 3,000 miles if we had built an engine.
I've never really gotten into PCV valve technology, as it's never been an issue on any engine I built. I simply bought a stock rated PCV valve for a similar cubic inch, and HP factory engine. I've also never had a problem with an engine breathing too well, and causing the PCV to suck oil into the intake. My recent 464 BBC engine has a PCV valve, and twin monster sized Moon valve cover breathers, and after a couple weeks of running I had the carbs off, and no sign of any oil getting into the intake.
I think if a PCV valve is properly located, and good valve covers used, plus a good engine, it shouldn't suck oil out of the valve covers.
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  #28 (permalink)  
Old 08-02-2013, 06:53 PM
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pcv sucking oil

Hey guys, can I ever relate to this problem.
I just finished a trip from Fla to Mass. towing a small boat and had to put one quart of oil in my motor every hundred miles due to the pvc valve sucking oil. I have a new and well oiled L-31 crate motor. The only thing I changed was the rocker arms to comp cam stamped rollers 1.52 ratio. I tried different types of pcv valves and so far have not remedied that problem. Right now I've disconnected the pcv completely and use breathers in both valve covers. No more oil disappearing, no more hearing ballbearings ratteling around when towing under loads. Pulls cleanly up to the redline with no blow-by. Hate to think how dirty my valves may be from all those miles of extra oil in the combustion chamber and intake.
Finally someone else is having this same problem and has saught to do what I wanted to do, use a separator inline with the pcv valve.
I would use taller valve covers but the alternator output lug prevents my using them.
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Old 08-03-2013, 10:19 AM
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Originally Posted by 1971BB427 View Post
I think if a PCV valve is properly located, and good valve covers used, plus a good engine, it shouldn't suck oil out of the valve covers.
I agree. My boss (At the time) bought a car with a 700+ hp big block in it. it used belt-driven vacuum pump and catch can for a PCV system. It would suck oil like crazy. all they did in the end was baffle the valve cover and it stopped the coil consumption.. and that engine was running AN-10 hose for PCV.
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Old 08-04-2013, 04:44 PM
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Quote:
Originally Posted by Bowtie Believer View Post
Right now I've disconnected the pcv completely and use breathers in both valve covers.

Uuuuh you realize that now you are not venting any of the nasty acidic vapors and blow by in the crankcrase?
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