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PCV valve? |
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pedricd 
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Joined: September-01-2016 Location: Northwest ohio Status: Offline Points: 75 |
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 Topic: PCV valve?Posted: May-24-2019 at 9:45pm |
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Was trying to tune up my carb after rebuild, I hooked up a vacuum gauge using a tee to the PCV line. Was only reading 5...thought that seemed pretty low.... pulled hose off of PCV valve, put my finger over the open end and boom 15 and the idle shot up.
So is this cut and dry that I have a gunked up/bad PCV valve (or am I whiffing on something)? |
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11093 |
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Posted: May-24-2019 at 10:05pm |
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Was the PCV valve plugged into the valve cover when you were getting the 5 inch reading with the T in the line? It should have been plugged in if it wasn't.
For the price of a PCV valve, I'd get another one to compare results. |
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pedricd
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Joined: September-01-2016 Location: Northwest ohio Status: Offline Points: 75 |
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Posted: May-24-2019 at 10:14pm |
Yes, I was tee’d into the line with the PCV valve in the valve cover. Removing the hose from the PCV valve and putting my finger over the end is what I am comparing to |
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KENO
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Posted: May-24-2019 at 10:27pm |
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It sound to me like the PCV valve is stuck open maybe
Getting another valve would be a good start. From your old posts it looks like you have a Sport Nautique with a 351 Tell the parts guy it's for an 84 F-250 with a 351. Bring the old one with you to compare Was it running kinda lousy at 5 inches of vacuum? You could have a vacuum leak at the carburetor base gasket or spacer gasket also and plugging the PCV line compensates for that leak. From lotsa miles away over the computer I'd lean toward a vacuum leak being the problem and not your PCV but like I said a PCV valve is cheap and will give you some good troubleshooting info 
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pedricd
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Joined: September-01-2016 Location: Northwest ohio Status: Offline Points: 75 |
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Posted: May-24-2019 at 11:45pm |
It wasn’t running too terribly no...but I want to dial it in,I rebuilt only due to hard start after sitting for a minute (assuming float not closing properly, forcing WOT start). I wanted to tune the carb the “right” way using vacuum vs rpm/feel. I replaced the gasket between the spacer and the carb (cleaned up the surfaces), but not between the spacer and manifold. What concerned me is it was a stark difference between PCV in the mix and blocked off which is sounding like I am right to consider it not closing properly (ie causing a vacuum leak / leaning the mixture?). Add to that much more sensitivity to carb adjustments once blocked and higher RPMs I think it’s not right...? Yes, it is a 92 SPN, 351w pro boss HO with GT40 heads (carb + orig pro tech) I am going to get a new PCV and see what that does... Also what RPM do you all shoot for in gear? 600? |
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11093 |
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Posted: May-25-2019 at 9:00am |
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600 sounds reasonable.
If you happen to need gaskets, get a couple of these in the link link One above the spacer and one below Nothing really "marine" about them, they just fit right And don't forget to update the thread with whatever you find. |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3749 |
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Posted: May-25-2019 at 2:23pm |
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I have a GT40, I believe my idle RPM is approx 700-750.
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KENO wrote: