Why does my motor run poorly with the PCV? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-11-2007, 05:59 AM
nat nat is offline
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Why does my motor run poorly with the PCV?

I determined that with the PCV valve hooked up, my SBC 350 will not idle right, it just fluctautes up and down. With the line removed and capped off it sounds great, no RPM fluctuations.

My setup is the PCV in the passenger valve cover and a K&N oil breather/filter in the driver's side valve cover.

Could I be drawing fresh air in from the oil breather? Is there that much vacuum pumping going on? Could I just get another breather/filter and get rid of the PCV? Thanks for the advice. This all came up when I started my TBI conversion project.

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Old 03-11-2007, 08:00 AM
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Have you replaced the PCV? They can leak and cause erratic idle. And just becasue it rattles when you shake it doesn't mean it's good.
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Old 03-11-2007, 08:12 AM
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Sounds like it was tuned without the PCV, and now with it hooked up it is drawing too much air under the throttle blades.
PCV valves are engine specific, the wrong one can flow too little or too much air.
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Old 03-11-2007, 03:27 PM
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Quote:
Originally Posted by nat
Thanks for the advice. This all came up when I started my TBI conversion project.

Welcome to the site NAT.
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Old 03-11-2007, 07:07 PM
nat nat is offline
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Quote:
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Welcome to the site NAT.
Thanks!!!
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Old 03-11-2007, 07:10 PM
nat nat is offline
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Problem Solved!!

I got some good info:

I was using an older style PCV instead of one for a fuel injection system. I bought a PCV for a 1990 Corvette with a FI 350 and now it runs just like it did with no PCV in the system. I guess the newer ones meter the flow of air better.

Any suggestions on fuel pumps? I am only getting 11psi and want 13-15psi. Is an intank model better? Mine is also really noisy, so I would like it back away from the engine compartment.
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Old 03-12-2007, 09:27 PM
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HiJack::

Does anyone have or is there a chart available that enables you to match you PCV to your vacuum? I don't believe a stock PCV that was designed for +/- 18" at idle will work correctly on modified engines with 10-13" at idle.

Thanks,
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