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Author Topic: PCV Valve Questions  (Read 778 times)

Offline D. Mailan

  • Posts: 37
  • Name: D. Mailan
PCV Valve Questions
« on: December 21, 2021, 11:03:54 PM »
Hello All,

I hope everyone is enjoying the holidays. I am working on a 1958 Coupe de Ville and the previous owner added a PCV system to the car many years ago. The sytem looks very similar to the mid 60's PCV systems. The car has an eldelbrock 1406 carburetor and runs very well with it. Ive noticed that recently the car idles smothly but has small hiccups. It also has a lot of oil residue comming from around the carburetor-intake gasket and phenolic spacer.

I was wondering if anyone has dealt with a pcv system before and what kinds of issues have come up with them.

I heard that the pcv valve can go faulty can cause the idle to be thrown off a little. Has anyone encounterd that before?

Has anyone installed a pcv system on a Cadillac from the 50s or early 60s? Did it affect your carburation?

Any thoughts, considerations, or ideas will be greatly appriciated.   
Derick
 

Offline James Landi

  • Posts: 2377
  • 2007 XLR
  • Name: James Landi
Re: PCV Valve Questions
« Reply #1 on: December 22, 2021, 07:48:20 AM »
I'll get the discussion started with some observations... As you know, cars without pcv were designed to pump noxious crankcase blowby out from under the car with a metal tube that extends under the engine.  As the engine ages, it develops more blowby, and even a serviceable, well running engine can become both embarrassingly smokey and unpleasant to be in.  All that said, it does not require much vacuum to clear the blowby.  Judging from your set up, there may be far too much vacuum present, so it's sucking up oil--- another issue: the set up is likely missing an internal baffel inside the valve cover that would ensure engine oil is not being sucked into the pcv system.  Hope this helps,  James

Offline fishnjim

  • Posts: 2422
  • Name: J. Bozin
Re: PCV Valve Questions
« Reply #2 on: December 22, 2021, 09:06:17 PM »
Only one picture but from the fuel pump location it looks like they tapped into the valley pan or ran the hose from the back where the tube was under the manifold.  Probably needs a little service.   That hose looks very suspect and cracked.   I'd change it and the PCV valve first.  They can get a little gummed up.   You can pull the carb and clean the insulator.   Is the carb heater passage blocked off?   There's exhaust that flows from the center of the intake manifold and under the carb.   Also a source of issues with carb performance.   Especially if it's running rich, it soots up under there.
There were several iterations of PCV until they kinda got it right, and some go into the air cleaner with a filter to coalesce the oil droplets.   Yours appears to be going straight into the carb base at the vacuum port, so they might have re-routed something else for the brakes?   I suspect your having some vacuum control issues now.   One of the trade offs.
The "58 Owners Club may have more info on this.   I know we debated it a few times over there.   

Offline D. Mailan

  • Posts: 37
  • Name: D. Mailan
Re: PCV Valve Questions
« Reply #3 on: December 22, 2021, 10:59:44 PM »
As it so happened, I spent several hours this morning taking the carburetor off. I cleaned the spacer and replaced the gaskets in between the intake, spacer, and carburetor. That was very dirty but fun. :D I did notice that after I cleaned the spacer, it was marked with a GM stamp. The car started right up and it idles much better but I still feel a small hiccup once in a while. Maybe it’s me not realizing it’s a 60 year old car. But I’d like to try and make it a little smother. I did adjust the carburetor again and the hiccup still happens. I suspect the pcv valve and hose that goes to the blow by tube.

The exhaust crossover passage is blocked so the carburetor and spacers don’t get overheated or warped. The vacuum for the brakes comes from the rear of the carburetor so it is not affected by it.

Some time ago, I removed the tube that went from the driver side valve cover to the air cleaner after I realized that the location of where it went in the air cleaner, coated the filter in oil and suffocated the engine. I attached a picture of where the tube came from on the valve cover. I have some extra 59 valve covers and will replace it later.

I plan on replacing the hose that goes from the blow by tube on top on the valley pan to the pcv valve soon. As well as getting a new pcv valve. I heard that certain makes and models have special pcv valves calibrated to work with the carburation and engine vacuum. Since mine was added on and wasn’t on it originally, should I get the exact one that is on the car now or would any pcv valve work? Possibly ones from the 60s era Cadillacs?

Thanks again,
Derick

 

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