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PVC valve
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59 in Calif
Posted 2017-10-13 6:07 PM (#550252)
Subject: PVC valve


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Location: Hayward, Calif
Hey Guys, Is a PVC valve specific for a particular eng, carb, and air cleaner ?? In other words, is the spring inside the valve set to operate at different preset inchs of vacuum depending on different eng and carb applications ?? The reason I ask is I finally got the PVC system hooked up. 59 Dodge with a 76 Chry 360 with stock Chry electronic ign. We took it out for a short drive, upon returning when parking it in the garage, at eng idle speed, it started losing Rpm. in gear. Shifted to neutral, gave it some gas and it came out of it. Back in gear, it did it again. Neutral and gas again ok. Before we left I reset the IA timing from 10 BTDC to 8 BTDC as I didn't like the way it was running at 10 BTDC. It acts and sounds better set at 8. And holding 21 inchs of vacuum at idle. The carb is an Edlebrock 600 CFM with a Weiend alum manifold. I didn't have the time to check it out further then, but plan to do so this weekend. Thanks, Jerry
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mikes2nd
Posted 2017-10-13 11:20 PM (#550267 - in reply to #550252)
Subject: Re: PVC valve


Expert 5K+

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some pvc's have springs, mostly are just a flapper easily moved by small vacuum. You have a standard rattler? You can shake it easily?

There are "tunable" pvcs.

this is the real deal and 129$

https://www.youtube.com/watch?v=nd92jPRH3YY


http://mewagner.com/?p=444

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BigBlockMopar
Posted 2017-10-14 4:06 AM (#550273 - in reply to #550252)
Subject: Re: PVC valve



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Location: Netherlands
Stock style pcv's come with various air flows.
You'll need to pick the one with the least amount of idle air flow, so the engine idle isn't affected too much it.

By your post it sounds like the pcv is venting too much (crankcase)air into the carb, thereby leaning out the mixture, which in turn leads to a rough idle.
Pinch down the hose to the pcv as a test and I'm sure you'll find idle quality will be improved considerably.

On one hand you need enough airflow to have a suitable crankcase ventilation, mainly to prevent moisture buildup in the engine, causing white sludge.
You living in a warmer climate I doubth you have much sludge forming anyway, so I think you could do with a pcv with less idle by-pass air flow.

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Powerflite
Posted 2017-10-14 10:49 AM (#550287 - in reply to #550252)
Subject: Re: PVC valve



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To me, it sounds like you are coming off of a fast (cold) idle setting on the carb to the hot setting. Did you adjust that? You have to get the car hot enough to fully disengage the choke to be able to adjust it.

When I installed a PCV (not PVC polyvinyl chloride) setup, I didn't notice anything different in the way the motor ran and certainly not anything that was variable.
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59 in Calif
Posted 2017-10-14 10:51 AM (#550288 - in reply to #550273)
Subject: Re: PVC valve


Elite Veteran

Posts: 1102
1000100
Location: Hayward, Calif
I think you are on the right track ! We took it out again yesterday and it was ok until returning home again. My first thought was to set the idle up a bit as it only does it in gear. Water temp and oil press in the normal range. My second thought was to insert a smaller rubber hose inside the hose from the base of the carb to the PCV valve to reduce some of the vacuum air flow. I'm planning to change the oil today , so will have a chance to play with it a bit. There is only 700 miles on this completely rebuilt eng so we should be coming out of the 'break in' phase. Thanks, Jerry
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Mopar1
Posted 2017-10-14 3:27 PM (#550293 - in reply to #550252)
Subject: RE: PVC valve



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59 in Calif - 2017-10-13 5:07 PM

. 59 Dodge with a 76 Chry 360
i'd think all you need to do is look up the correct PCV valve for a '76 360........
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59 in Calif
Posted 2017-10-14 3:50 PM (#550294 - in reply to #550252)
Subject: Re: PVC valve


Elite Veteran

Posts: 1102
1000100
Location: Hayward, Calif
I went out and played with it awhile this AM. The eng was at operating temp. It seems to only do it after eng warm up. doesn't do it when it's cold. I put a smaller rubber hose inside the hose to the pcv valve and started eng. standing next to the fender I could hear the PCV valve chattering rapidly and lost 100 RPM in gear. Obviously that was the wrong thing to do, so took it back out and set the idle RPM up a touch. So will run it like that until I can come up with a better way to deal with this. I got that valve at Pep Boys because it was a nice shiny chrome unit that goes well with the chrome valve covers. Maybe that is where the problem is. I rarely shop at Pep Boys, but seemed like the thing to do at the time. Jerry
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ttotired
Posted 2017-10-14 5:47 PM (#550300 - in reply to #550252)
Subject: Re: PVC valve



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Diagnose the problem, don't guess

Your blaming the pcv, Why?

I am not sure if you were running the pcv system before or not (I didn't quite get that from your initial post)

To test a pcv, most I have come across, you just rattle them, if they rattle, theyre good, but easy to see if its causing the problem, plug it up.

Did connect the hose from the pcv and stick something in the hose, then go for a drive and see if its the same

I would also do a cylinder cut out test and a compression test (when hot)

You havnt said what idle rpm your chasing and if the engine has been cammed, high stall, ect ect

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59 in Calif
Posted 2017-10-14 7:04 PM (#550302 - in reply to #550252)
Subject: Re: PVC valve


Elite Veteran

Posts: 1102
1000100
Location: Hayward, Calif
OK Guys, think I got it. I got a PCV valve for 76 Chry and a new hose and installed it. That seems to have settled things down, no more near dying at idle in gear. The reason I was blaming the PCV valve , because the problem didn't exist before hooking it up. I was just running a blow by hose down the backside of the eng and was getting a little tired of the mess. We are planning an outing with it tomorrow so will see how it acts. Thanks for all your help. Jerry
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59 in Calif
Posted 2017-10-15 6:38 PM (#550343 - in reply to #550252)
Subject: Re: PVC valve


Elite Veteran

Posts: 1102
1000100
Location: Hayward, Calif
Hey guys, We took it out for a cruise today and all seems well. It didn't stumble at idle in gear. The 76 Chry PCV valve seems to have done the trick. I think the Pep boys valve was too big and allowing too much crankcase ventilation thru and leaning out the idle air/fuel mixture. Jerry
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