56 312 what pvc valve to use ?

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T

thessler

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Joined
Sep 20, 2019
Thunderbird Year
1956
Hi
I hooked up a pvc system on my 56.
After a long drive I'm getting oil spray out of my breather cap and spraying right back to the firewall.
This tells me I do not have negative pressure in the crank case.
The valve is plumbed from the rear of the carb to a grommet where the draft tube was.
So I'm thinking I have the wrong value installed, as they need to be sized for the application.
Just wondering if anyone has a successful conversion what part number vaulve you used.
Thank you, Tom
 
thessler said:
Hi
I hooked up a pvc system on my 56.
After a long drive I'm getting oil spray out of my breather cap and spraying right back to the firewall.
This tells me I do not have negative pressure in the crank case.
The valve is plumbed from the rear of the carb to a grommet where the draft tube was.
So I'm thinking I have the wrong value installed, as they need to be sized for the application.
Just wondering if anyone has a successful conversion what part number vaulve you used.
Thank you, Tom
Click to expand...


From what I gather the engines that have PVC valves are closed systems and do not have a breather on the valve cover or on the oil filler cap. The PVC valve closes when idling while it has high vacuum and opens when there is low vacuum while under load and the engine has high back pressure. PVC engines actually has a tube going from the valve cover to the breather that takes care of excesss back pressure. Hope this helps. You may have to do a search on PVC systems to be able to correct yours.
 
The small bird Tbird venders offer a PCV valve system is this where you purchased yours?
 
Actually I didn't buy a system. I just pulled out the draft tube and put a pvc grommet in its place.
I just think I have the wrong pcv # for my engine.
 
You definitely have an over pressure in your crank case. The original design was to be free breathing and you are interfering with that. If you insist on having a PCV valve I'd go with the kits the suppliers provide. It's an intricate system many don't understand. Do you do your own plumbing at home?
 
Piston rings worn out, excessive blowby. Did you put the pcv on because of oil thrown out oil cap?
 
No I put it in because it's just a better system than the draft tube.
Just need to tweak it a little and it will be fine.
 
curious if anyone is recommending/happy with the aftermarket PCV kits for engines never overhauled. i get a lot of blow-by on my 57.
 
southpaw said:
curious if anyone is recommending/happy with the aftermarket PCV kits for engines never overhauled. i get a lot of blow-by on my 57.
Click to expand...
Do a compression test. Do you drive it a lot? Could be as simple as stuck piston rings or worn out. No crank case ventilation system will help that.
 
thessler said:
Hi
I hooked up a pvc system on my 56.
After a long drive I'm getting oil spray out of my breather cap and spraying right back to the firewall.
This tells me I do not have negative pressure in the crank case.
The valve is plumbed from the rear of the carb to a grommet where the draft tube was.
So I'm thinking I have the wrong value installed, as they need to be sized for the application.
Just wondering if anyone has a successful conversion what part number vaulve you used.
Thank you, Tom
Click to expand...
Here is a kit made for a PVC

 
southpaw said:
curious if anyone is recommending/happy with the aftermarket PCV kits for engines never overhauled. i get a lot of blow-by on my 57.
Click to expand...
My 57 has a kit someone before me installed and it seems to work fine. They are very simple systems, all the PCV valve does is limit flow at high vacuum, such as idle, and allow maximum flow at lower vacuum. The rest is just plumbing. I think my engine was worked on at some point since it has very little blow by. If you get a lot of blowby a PCV isn't going to fix that since at idle it closes off to avoid a lean condition and at higher speeds when it has more flow it will never have enough flow to pull thru all the excess blowby. A PCV that isn't working right and isn't allowing flow means all the blowby must come out the oil filler tube. There are different PCV valves for different models and my presumption is that's because different engines needed different calibration of the amount of flow at different vacuum settings. So if someone just put on a PCV that "looked right and fit" it may be the wrong one. If I had nothing else to go on I'd look for a PCV valve for a mid to late 60s mustang 289 as a starting point.
 
I know I'm going to get some push-back, But just leave the original engineering alone. You are causing more problems than you can solve. Would you try to put emission controls on a Brass era engine? If you want to go so far on emission controls on old school technology, then sell the thing so you can go away from it and by a purpose built no emission vehicle and save the trials and tribulations not to mention the cost. The advances are amazing but very costly at this time. Don't discount and appreciate that what came before us. You can't change history. Live and learn.
 
Ward 57 said:
I know I'm going to get some push-back, But just leave the original engineering alone. You are causing more problems than you can solve. Would you try to put emission controls on a Brass era engine? If you want to go so far on emission controls on old school technology, then sell the thing so you can go away from it and by a purpose built no emission vehicle and save the trials and tribulations not to mention the cost. The advances are amazing but very costly at this time. Don't discount and appreciate that what came before us. You can't change history. Live and learn.
Click to expand...
yes excellent point. why mess around?... but pcv valves, a fairly simple technology (from my understanding), were added to basic carbureted engines in the 60's to decrease emission/pollution. however if the problem is in the cylinders, the valve wont help much, .appreciate the responses!
 
Ward 57 said:
I know I'm going to get some push-back, But just leave the original engineering alone. You are causing more problems than you can solve. Would you try to put emission controls on a Brass era engine? If you want to go so far on emission controls on old school technology, then sell the thing so you can go away from it and by a purpose built no emission vehicle and save the trials and tribulations not to mention the cost. The advances are amazing but very costly at this time. Don't discount and appreciate that what came before us. You can't change history. Live and learn.
Click to expand...
I don't think of a PCV as an emissions control, even though it is, but as a significant improvement in keeping contaminants out of the oil/engine. When the engine is idling/at slow speeds the road draft tube does nothing whereas the PCV pulls the blowby's combustion byproducts out, that includes acids, water, soot, carbon, etc. If an engine has excessive blowby a PCV isn't going to fix that. I think that's the initial issue the OP needs to determine and decide if it's something to try and fix. Since many of these cars only get driven a few hundred to few thousand miles a year having a fairly worn engine isn't the big deal it would be on the family buggy. If it starts well and doesn't have visible smoke that may be all that's needed to enjoy the drive. And it may also be that, as you say, leave well enough alone as far as the draft tube setup.
 
Get a valve for an engine that is close in size to yours. For example, a valve for a 302or 351 V8';s or a 300 CI six cylinder Ford should be about the correct size.
 
jimntempe said:
I don't think of a PCV as an emissions control, even though it is, but as a significant improvement in keeping contaminants out of the oil/engine. When the engine is idling/at slow speeds the road draft tube does nothing whereas the PCV pulls the blowby's combustion byproducts out, that includes acids, water, soot, carbon, etc. If an engine has excessive blowby a PCV isn't going to fix that. I think that's the initial issue the OP needs to determine and decide if it's something to try and fix. Since many of these cars only get driven a few hundred to few thousand miles a year having a fairly worn engine isn't the big deal it would be on the family buggy. If it starts well and doesn't have visible smoke that may be all that's needed to enjoy the drive. And it may also be that, as you say, leave well enough alone as far as the draft tube setup.
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If it's not pollution control, then what's the point? How long are you at idle for the road draft tube to not pull that stuff out of the crank case
 
Ward 57 said:
If it's not pollution control, then what's the point? How long are you at idle for the road draft tube to not pull that stuff out of the crank case
Click to expand...
The point is that it does a better job than the road draft tube. I'd prefer to get the blow by out all the time, including when I'm idling or going too slow for the draft tube to work. Any blowby that comes out the top breather will be oily and will slowly coat the underside of the hood and everything in the engine compartment with an oily film.
 
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