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Old 11-20-2012, 05:56 PM   #1 (permalink)
 
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PCV valve

I need high performance PCV valve. 1970 455 flat tops, #96 heads, Bullet (hydraulic roller) cam...230/238 530/530 on a 112. Suppose to have 4 degrees advance already in it, so its installed straight up. 0 lash and a quarter turn on 1.62 roller rockers.
Have about 9.5-10 inches of vacuum at 750-800 idle rpm. If I unplug ( and block off the carb and pcv tube) the PCV, I get 12.5 inches of vacuum.

I figure the current PCV is rated wrong for this application, therefore wondering if anyone has a P/N for a lower vacuum rated PCV.

Thanks!
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Old 11-21-2012, 02:10 PM   #2 (permalink)
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Well... strip my gears and call me shiftless... I think I have a similar issue and it didn't register with me until I read your post. I don't have an answer but I'm sure interested in hearing if someone does.

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Old 11-22-2012, 10:09 AM   #3 (permalink)
 
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I found one for a 1970 Chevelle 454 LS6.

Here's an interesting article.

Positive Crankcase Ventilation (PCV)
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Old 11-22-2012, 11:36 AM   #4 (permalink)
 
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I think I might do some "shade tree" testing by inserting an adjustable valve (plumbing dept at L or HD) in line with the PCV hose. Adjustment somewhere between fully open/closed and note the results. ?? Assume that the needed results will be less of a vacuum draw from the engine but enough for PCV action ??
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Old 11-22-2012, 08:00 PM   #5 (permalink)
 
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I feel like I should have between 12-14 inches of vacuum at 800 rpm, but I only have 9.5-10. My valve lash is 1/4 past 0, but its a consideration to go to 1/8 or even 0 lash to gain some more vacuum. Normally this wouldn't be necessary on this camshaft specs.

Trying to think outside of the box, I am going to try a different PCV and see if I gain some vacuum. Its possible the one I have now is rated for a closer to stock cam with 15-17 inches of vacuum.

I am always trying to learn more and pass information on, if it will help someone else.
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