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PCV Valve and TCS

Started by Houston747, March 09, 2023, 08:25:18 PM

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Houston747

I have a 70 Deville with the factory 472, I was wondering if anyone on here had any experience bypassing/disabling the PCV valve and TCS systems on these cars? Speaking of them, what is the exact location of them? And would disconnecting both affect the car negatively in any way?
A.AlRub

TJ Hopland

What do you hope to gain by removing the PCV? If you do remove it how do you plan to vent the crank case?  Fabricate some sort of draft tube but where would you plumb it in?  Seems like a heck of a lot of work to make things worse. 

Have you ever worked on an engine without a PCV?  They are a mess inside and those are the ones that get worked hard and often.  Something that doesn't get fully warmed up and worked a bit would be even worse.  Yes it started out as an emissions thing but it turned out to help the internals stay cleaner by forcing air to circulate through the engine. It pretty much has zero effect on performance or economy.  The vacuum flow it uses and gasses it collects are just a planned part of the tune and the overall system of the engine and car. Its when you start altering anything in that system that things can start to change especially if you don't understand the systems are and how the interact and how you would need to compensate for one system being removed or altered. 

The TCS probably isn't making much difference either. Some engines may respond differently with it bypassed and others it won't be noticeable.  Same thing if the distributor is using ported or manifold vac.  Some it makes a difference and others not so much.  It just seems to depend on the rest of the tune and condition of the system.           
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364

The question of eliminating the PCV can be answered simply by telling you that I have a PCV on my race car.  The only accomplishment by eliminating it and going to a road draft vent would be the sensory enhancement of an atmosphere of crankcase gas in the car at stoplights.
As far as the thermal switch, I am assuming you are talking about the switch in the vacuum line to the vacuum advance. Eliminating this circuit and hooking up your vacuum advance to the timed vacuum port on the carb would guarantee summertime overheating in any type of city traffic.
If you are talking about the Transmission Controlled Spark (TCS), you would, to gain any improvement, have to re calibrate the advance curve of the distributor and re jet the carb.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Chopper1942

If you like the smell of crankcase fumes, a sludged up engine, oil contaminated with water and combustion byproducts, get rid of the PCV valve, install an unfiltered breather on a valve cover and rig up draft tube on the other valve cover or the oil pan. Or better yet, just pull your 472 out and install a stock 331.  You won't have to worry about the "emission devices" that are on the 472 that don't hurt performance or economy and help the longevity of your engine. (Sarcasm intended)

My suggestion is to install the correct PCV valve and new vacuum hoses.  New vacuum hoses for the TCS. Put a vacuum pump on the vacuum advance and see if it moves and holds vacuum. If not, replace the vacuum advance.  This would be better time and money spent on your vehicle.

TJ Hopland

The vacuum pump Larry is talking about is the hand type with a built in gauge used for diagnostics.  Basically he is saying just make sure the system is working, it may not be and just fixing it will maybe gain you the performance you are looking for.  If the vacuum advance isn't working (which is common with age) the performance will be kinda flat.

I'm not specifically recommending harbor freight just giving an example of the type of tool we are talking about that is useful for many automotive testing and repairs. Parts stores will have them.  The big online places will have them. I would say this is a must have tool for anyone that tinkers with cars.

https://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-63391.html



StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Chopper1942

Great reply TJ.  I've been doing this for so long that I sometimes forget that everyone doesn't have the basic diagnostic tools.  The one you have pictured will work great for 1 man brake bleeding too.