Evaluate my PCV system

Abchoppers

Abchoppers

Member
1956 Mercury with 312, car came with a PCV system that was routed from valley pan to intake, after many suggested this could foul up the rear cylinders I moved things around.

I have a valley pan that has what was perfectly described to me as a tea pot looking port at the rear with a tube. I’ve attached a vacuum hose to that tube and connected the other end to my new Holley 4 bbl rear PCV port. I’ve placed the pcv, a v100, in between. The suction side is facing the carb, so the carb would be pulling through the PCV valve. Before assembly I shook the valve and was able to blow through it, so I think it’s good. My oil filler has a breather cap on it, although I have bought a new cap with a hose port I plan to run back into the air cleaner.

Here’s my question - when running the car, at idle or higher rpm’s, there is no suction from the oil fill. It actually feels like it’s blowing out slightly. After running the car if I remove the oil fill cap there is smoke inside that slowly rises out. If I start the engine again the smoke does get sucked back down. With cap in place I never get any blow by smoke escaping. Should I see more suction at the fill tube? Any suggestions on the overall system to improve it? Maybe there is suction since the smoke does show some when running, but it definitely doesn’t pull a thin tissue to the fill tube when I test it

Thank you in advance for your time
Ryan
 
Answers to these questions may help give you the information you need...

1. Do you happen to have the beehive canister on the side of the block? If so, this is another area where air is being sucked into the crankcase under vacuum through your carb's PCV line.

2. What is your vacuum gauge reading at idle?

3. What is the condition of your piston rings? worn engines with low compression numbers will have a lot of blow-by of course and this will "blow smoke" out of any place where the block is vented.

4. "After running the car..." the smoke you see when removing the cap on the fill tube could be steam depending on how much moisture is in the crankcase and how little time you have run the engine at a temperature that will evaporate all of the moisture in the block.

I would suggest running the car down the road for at least 30 minutes on your next test and see how things are going when you pull back into the garage.
 
Hot Rod Reverend said:
Answers to these questions may help give you the information you need...

1. Do you happen to have the beehive canister on the side of the block? If so, this is another area where air is being sucked into the crankcase under vacuum through your carb's PCV line.

2. What is your vacuum gauge reading at idle?

3. What is the condition of your piston rings? worn engines with low compression numbers will have a lot of blow-by of course and this will "blow smoke" out of any place where the block is vented.

4. "After running the car..." the smoke you see when removing the cap on the fill tube could be steam depending on how much moisture is in the crankcase and how little time you have run the engine at a temperature that will evaporate all of the moisture in the block.

I would suggest running the car down the road for at least 30 minutes on your next test and see how things are going when you pull back into the garage.
Click to expand...

Thank you for the reply
1. The canister on the side of the block is removed and there is a block off plate there now. I should have mentioned this in original post but I forgot

2. Vacuum is a steady 20 inches at idle

3. I don’t know the condition of the rings or the engine, it doesn’t blow any smoke out of the exhaust and has good power if that means anything

4. I never thought about moisture, it’s definitely pure white. I’ll try what you said about giving it a good run and checking again, great tip thank you

Thanks again for your time
Ryan

I just realized I watched your video on the hidden vacuum leak last night on YouTube! Great stuff!
 
Ryan,

there is quite a bit more on my website... I used to post a lot of the build here on the forum but my posts got rather lengthy, had a lot of photos, and I started adding videos as well. You can see my original forum post here: https://www.fordbarn.com/forum/showthread.php?t=145936 It has quite a few views - the guys here on the forum were very helpful as you can read through the thread and see their answers.

My website blog is here: https://www.hotrodreverend.com/blog

hope it helps
 
When you’re checking for vacuum at the fill tube, try pulling the dipstick and putting some tape over it. Modern engines have those sealed. Otherwise it’s an air intake, and you’re looking for very low vacuum levels at idle at that fill tube.

I think DryLakesRacer has some post about that at yblocksforever. Might try a search.
 
Hot Rod Reverend said:
Ryan,

there is quite a bit more on my website... I used to post a lot of the build here on the forum but my posts got rather lengthy, had a lot of photos, and I started adding videos as well. You can see my original forum post here: https://www.fordbarn.com/forum/showthread.php?t=145936 It has quite a few views - the guys here on the forum were very helpful as you can read through the thread and see their answers.

My website blog is here: https://www.hotrodreverend.com/blog

hope it helps
Click to expand...

I’ll check it out, thank you
 
miker98038 said:
When you’re checking for vacuum at the fill tube, try pulling the dipstick and putting some tape over it. Modern engines have those sealed. Otherwise it’s an air intake, and you’re looking for very low vacuum levels at idle at that fill tube.

I think DryLakesRacer has some post about that at yblocksforever. Might try a search.
Click to expand...

I’ll try that, thank you. Drylakesracer has helped me out over on the HAMB, I’ll search that on yblocksforever
Thanks again
 
I was a licensed smog check/fleet mechanic here in CA for 30 wasted years of my life. If the engine is worn you "do not" want to install a pcv valve just leave the road draft tube alone and drive it. On an engine with excess blowby the pcv will with suck in the blowby along with oil and coats the intake valves. It will continue to get build up on the valves creating hard carbon until there is so much of it the air can barely flow into the cylinders.

If the engine is sealed the PCV valve should suck a piece of paper down against the fill tube at idle unless the engine has too much blowby, too many air leaks in the crankcase, the valve is defective, or the hose has collapsed. You must use a hose rated for gas or it will quickly become spongy from the oil and gas fumes and collapse under the vacuum. You could have an intake leak but it would idle poorly. You can run propane around the intake and carb base to check for leaks, The idle will change when the propane passes over the vacuum leak. Pull the hose out the valley pan and make sure it is sucking. PCV valves are calibrated for the size of the engine, you could have a valve that is a little too small. I've never installed one on an engine that never had one, but I imagine you would choose one from a similar size engine like a 1968-1970 Ford 302, that should be close enough. They generally last 30,000-50,000 miles before the spring loses its calibration. They should be replaced at that interval, but nobody ever does it until they fail and the engine won't idle.

You want the incoming air to the breather to be filtered otherwise your pcv valve is sucking dirt into the engine and doing more harm than good. Normally a factory pcv would be located on one valve cover and the breather on the opposite side so fresh air is pulled down into the crankcase back out the opposite valve cover flushing out all of the blowby gases to prevent the oil from getting contaminated which creates an acid. The breather would have a hose going to the inside of the air filter housing where the air has already passed through the filter. There are times when the pcv cannot handle all of the blowby., then it goes out the breather and into the air cleaner housing where the engine burns it. This prevents it from escaping into the atmosphere and creating smog.

If you suspect air leaks in the crankcase, I've never tried it but You could put a hair dryer on the fill tube and check around the engine for air coming out. We had a smoke machine at work that used heated mineral oil for testing evap systems on vehicles with charcoal canisters. If you have ever had a car fail the evap test and it wasn't the usual bad gas gap that is how you find the leak. You fill the entire gas tank and evap system with smoke and see where it comes out, it stinks the hole shop up. There is a good chance on an old engine it is tired and then I wouldn't worry about it and just drive it. PCV valve on a worn engine is going to suck up the excess blowby along with oil and it will coat the valves which will turn to a hard carbon until there is so much of it on the valves the air can barely flow past it.

You can do a compression check on the engine and then repeat it with a couple squirts of oil in each cylinder. If the compression comes up the rings are worn.

I have early cars with no pcv valves, and I don't drive them that much. I just change the oil when it gets slightly dirty. If you are building a new engine and want to install a pcv valve you can otherwise I wouldn't worry about it on an old engine.
 
Flathead Fever said:
I was a licensed smog check/fleet mechanic here in CA for 30 wasted years of my life. If the engine is worn you "do not" want to install a pcv valve just leave the road draft tube alone and drive it. On an engine with excess blowby the pcv will with suck in the blowby along with oil and coats the intake valves. It will continue to get build up on the valves creating hard carbon until there is so much of it the air can barely flow into the cylinders.

If the engine is sealed the PCV valve should suck a piece of paper down against the fill tube at idle unless the engine has too much blowby, too many air leaks in the crankcase, the valve is defective, or the hose has collapsed. You must use a hose rated for gas or it will quickly become spongy from the oil and gas fumes and collapse under the vacuum. You could have an intake leak but it would idle poorly. You can run propane around the intake and carb base to check for leaks, The idle will change when the propane passes over the vacuum leak. Pull the hose out the valley pan and make sure it is sucking. PCV valves are calibrated for the size of the engine, you could have a valve that is a little too small. I've never installed one on an engine that never had one, but I imagine you would choose one from a similar size engine like a 1968-1970 Ford 302, that should be close enough. They generally last 30,000-50,000 miles before the spring loses its calibration. They should be replaced at that interval, but nobody ever does it until they fail and the engine won't idle.

You want the incoming air to the breather to be filtered otherwise your pcv valve is sucking dirt into the engine and doing more harm than good. Normally a factory pcv would be located on one valve cover and the breather on the opposite side so fresh air is pulled down into the crankcase back out the opposite valve cover flushing out all of the blowby gases to prevent the oil from getting contaminated which creates an acid. The breather would have a hose going to the inside of the air filter housing where the air has already passed through the filter. There are times when the pcv cannot handle all of the blowby., then it goes out the breather and into the air cleaner housing where the engine burns it. This prevents it from escaping into the atmosphere and creating smog.

If you suspect air leaks in the crankcase, I've never tried it but You could put a hair dryer on the fill tube and check around the engine for air coming out. We had a smoke machine at work that used heated mineral oil for testing evap systems on vehicles with charcoal canisters. If you have ever had a car fail the evap test and it wasn't the usual bad gas gap that is how you find the leak. You fill the entire gas tank and evap system with smoke and see where it comes out, it stinks the hole shop up. There is a good chance on an old engine it is tired and then I wouldn't worry about it and just drive it. PCV valve on a worn engine is going to suck up the excess blowby along with oil and it will coat the valves which will turn to a hard carbon until there is so much of it on the valves the air can barely flow past it.

You can do a compression check on the engine and then repeat it with a couple squirts of oil in each cylinder. If the compression comes up the rings are worn.

I have early cars with no pcv valves, and I don't drive them that much. I just change the oil when it gets slightly dirty. If you are building a new engine and want to install a pcv valve you can otherwise I wouldn't worry about it on an old engine.
Click to expand...
That’s a ton of good info flathead fever, much appreciated. My next move is to run a compression test and see how healthy the engine is. Today I put the new oil filler cap on with a hose routing into the top of the air cleaner. I also ordered a new PCV valve just to give it a shot
Thanks again
Ryan
 
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