Leave the pcv valve on or take it out pros and cons

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Basin_Runner355
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Leave the pcv valve on or take it out pros and cons

Post by Basin_Runner355 » Fri Feb 02, 2018 5:18 am

I just put a new Holley 750 DP on my boat and had it set. I was thinking about taking out the pcv valve because i bought me a bigger flame arrestor and it dose not have a spot to hook one up at so got me thinking if i really need one. My concern is 1 will i need to get my carb reset because i just had to pay somebody to set it. Concern #2 i wound be worried about It comming out and going through the prop. So is there anyting to gain from takingnkt out. I read that airboats don’t need them causes of the high rpms and constant load they are under. Just want some other ppla opinions and i don’t feel like having to pay somebody to reset the carb unless i will gain from it.
14ft diamond back mild zz4 355sbc pushin 450 hp 450 TQ 2:1 belt drive reduction with a 3 blade sensenich 78Jw series

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Smuggler
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Re: Leave the pcv valve on or take it out pros and cons

Post by Smuggler » Fri Feb 02, 2018 6:53 am

I ditch them myself.. Here is a old thread on the subject.. viewtopic.php?f=48&t=12253&p=129181&hil ... ve#p129181

SWAMPHUNTER45
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Re: Leave the pcv valve on or take it out pros and cons

Post by SWAMPHUNTER45 » Sat Feb 03, 2018 6:22 am

We run a PCV system and all the Branch engines are built with them when they leave his shop. In short the objective is to pull clean air through the engine while it is running. This in turn will lower the presence of dirty acidic blow by and make for a cleaner and longer lasting engine.

Race cars don't use them because they get rebuilt every few races or at the end of a season. If you have an engine built to last my advice is run a PCV system pulling from one valve cover and vented on the other. If oil spray is a concern a baffled draw point is utilized.

Basin_Runner355
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Re: Leave the pcv valve on or take it out pros and cons

Post by Basin_Runner355 » Sat Feb 03, 2018 8:16 pm

I was looking today and i only have a pcv valve on one valve cover going to the carb the other valve cover just has a open hose running to the air filter. Is that ok that’s how i bought it. Or do i need to put one on both sides
14ft diamond back mild zz4 355sbc pushin 450 hp 450 TQ 2:1 belt drive reduction with a 3 blade sensenich 78Jw series

SWAMPHUNTER45
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Re: Leave the pcv valve on or take it out pros and cons

Post by SWAMPHUNTER45 » Sun Feb 04, 2018 8:01 am

That's perfectly fine

You draw air through the engine that way.

It enters on the side with the hose to the covered breather which should filter it and keep out contaminates. The engines vacuum pulls the clean air into the engine and draws it through the internal workings then into the intake to be burned.

The valve covers are usually made with a baffle to prevent oil ingestion or the builder using an aftermarket valve cover will place the draw point away from a rocker. The valve itself regulates the amount of vacuum so replace it with an identical part should you ever need to change it. My set us uses a valve that was for a 400 cid small block Chevy it is what the builder found to offer the ideal amount of draw for my build.

That's the objective and it sounds as if it is set up properly.

One caveat to this would probably be that if your running a WaterThunder or other engine that is living up in the very high rpm range and built without a PCV by design that would really be better served to be vented. If your running a traditional power application posative crankcase venting will help longevity and reduction of gasses and contaminates from the combustion process.

When in doubt check with your builder.

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Re: Leave the pcv valve on or take it out pros and cons

Post by loudmouse » Sun Feb 04, 2018 12:17 pm

To use a pcv properly the engine needs to be sealed so the pcv system can pull a vacuum on the entire crankcase. If the engine is a stockish type this will work well. If you are using a pcv with one valve cover vented then all ur doing is allowing unmetered air to enter the engine and creating a leaner running engine. Not good. If you want to use a vented system then remove the vacuum hose to the engine and vent both valve covers.
If you have an oil fill cap that is sealed then use the large port on the back of the carb baseplate. Come out and split it with a Tee and go to both valve covers. This pulls a vacuum on the crank case and evacuates all gases that escape the combustion chambers.
The way urs is now the carb would have to be richened up to compensate for the unmetered air. Also causes idle tuning issues.
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
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Re: Leave the pcv valve on or take it out pros and cons

Post by loudmouse » Sun Feb 04, 2018 1:49 pm

There is no reason for clean, as u call it, air to enter the crank case. The sole reason for pcv is to evacuate gases which can accumulate into pressure inside the crank case which causes oil seals to leak. Thats it and nothing more. A negative pressure situation inside the crank case is desirable for ring seal, oil control and it removes air mass from the crank case which lessons air weight under the pistons which results in a small increase in power output in a performance engine. For modern engines in automobiles another reason is to control emissions.

For a mild stockish engine in good condition, a sealed pcv will work very good. A performance engine which has a significant amount more crank case gasses (blow-by) a vented system to a catch can is better. A sealed engine with a vacuum pump is best.
Not much more to it. Pick ur method, set it up properly, and you won't have to worry about it.
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:

SWAMPHUNTER45
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Re: Leave the pcv valve on or take it out pros and cons

Post by SWAMPHUNTER45 » Sun Feb 04, 2018 1:57 pm

Positive
Crankcase
Ventilation

Not much more needs to be said.

Detroit designed the systems to pull from one valve cover and draw through to the other. If your 350 is set this way and you have no issues leave it alone your good.

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Re: Leave the pcv valve on or take it out pros and cons

Post by SWAMPHUNTER45 » Sun Feb 04, 2018 2:11 pm


loudmouse
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Re: Leave the pcv valve on or take it out pros and cons

Post by loudmouse » Sun Feb 04, 2018 2:34 pm

My last post on this so maybe you will understand how the pcv works. When the SEALED engine has a pcv hose connected from the crankcase to the intake or carb, the engine vacuum is applied to the entire crankcase. Once the crankcase vacuum level matches the vacuum of the intake, no more air moves through the system until gasses escape the combustion chamber into the crankcase. This adds pressure to the CC and the pcv removes it back to the vacuum level of the intake. This is a constantly operating system removing only the escaped gasses(blow-by). If the engine crankcase is open anywhere (vented) u create a constant vacuum leak that causes the engine to operate in a leaner condition as none of this consumed air is metered for fuel. Only the air through the carb is metered with fuel. Any air entering the engine below the booster IS NOT METERED FOR FUEL= A lean operating engine...
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:

loudmouse
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Re: Leave the pcv valve on or take it out pros and cons

Post by loudmouse » Sun Feb 04, 2018 4:14 pm

Quote: For a mild stockish engine in good condition, a sealed pcv will work very good. A performance engine which has a significant amount more crank case gasses (blow-by) a vented system to a catch can is better. A sealed engine with a vacuum pump is best.
Not much more to it. Pick ur method, set it up properly, and you won't have to worry about it.

Did you miss this part of my post? :dontknow:

BTW the condensation that mixed with oil in ur catch can mostly came from the travel of vapors from the engine to the can and the can itself not from the engine. Only the oil and heat was from the engine. IF you had a good crank case designed vent system there would be very little oil in the can unless the rings are gone. Just Sayn.
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:

loudmouse
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Re: Leave the pcv valve on or take it out pros and cons

Post by loudmouse » Sun Feb 04, 2018 4:42 pm

:salute: oNo problem I have done it also when skipping through a thread.

Yes condensation is in the engine when it's first started cold and after its shut off and allowed to cool. After the engine is running, the oil will wash the moisture off the inside surfaces and it mixes(milky) with the oil. That's why a thermostat is important to get the engine up to temp to burn off (evaporate) the moisture from the engine and oil. The catch can catches vapors that are hot. As this vapor travels to the can it starts to cool causing condensation but inside the engine the temperature is constant and therefore no condensation. Now an alcohol or E fueled engine is a whole nother story. It's always best, when u start ur engine, let it warm completely to operation temp b4 shutting it off. Otherwise, you create jus enough heat to cause more condensation and not enough heat to evaporate the moisture from the oil. If you don't do that on alcohol engines when u drain the oil there will be about a quart of water or more in the pan.
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:

Basin_Runner355
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Re: Leave the pcv valve on or take it out pros and cons

Post by Basin_Runner355 » Sun Feb 04, 2018 9:05 pm

Well i been wanting to put some long tube headers seems like now i have a good excuse to all you do is run a line from the valve cover piped into the header? And my boat has been having trouble with tuning the idle it’s been to 3 different ppl and nobody can get it to stop loading up
14ft diamond back mild zz4 355sbc pushin 450 hp 450 TQ 2:1 belt drive reduction with a 3 blade sensenich 78Jw series

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Re: Leave the pcv valve on or take it out pros and cons

Post by loudmouse » Sun Feb 04, 2018 9:52 pm

Basin, that problem can be easily fixed but it might not be entirely a problem with the carb.

For the money, I don't think long tube headers are worth the change for $$ spent unless u have to buy headers anyway.
No need to weld in a header evac tubes, just run a catch can vented system. Super easy to do.
Last edited by loudmouse on Sun Feb 04, 2018 11:05 pm, edited 1 time in total.
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:

SWAMPHUNTER45
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Re: Leave the pcv valve on or take it out pros and cons

Post by SWAMPHUNTER45 » Mon Feb 05, 2018 9:21 am

Regardless of where you go from here the best advice anyone could offer is to fix your current problem before you move forward making alterations to the system. Once you have it fixed where it is running properly and jetted safe then if you want to change draw points or add in the catch can or exhaust type bung system you will be in a better place to note any effects.

Keep in mind Blackwater has told you that you need to check or drain the catch before each trip. These were designed to catch oil in race engines and in this application it becomes more of a condensation or water collection point. If you have a larger catch and get lazy your gonna give the engine a straw to suck collected water.

We only see evidence of condensation in our engines in the winter months and it is trace or minimal. As a discussion point it shows more with a natural oil and when using the Lucas additive and less with the synthetic products like Amsoil or Mobil1. The standard cross flow PCV works well for us my oil stays clean and the engines last for ever. No reason for me to alter the system but for others in extreme applications it may be a advisable modification, I can see in the tour boat arena it may be a good choice as the heat and cool cycles are so excessive.

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Re: Leave the pcv valve on or take it out pros and cons

Post by loudmouse » Mon Feb 05, 2018 10:07 am

:thumbleft: Swamp knows what I be sayn.

I can help with the carb issues if you can do the work.. or make a trip to Fl stop by my shop we'll FIX it and you could ride a few days b4 heading back home
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:

Basin_Runner355
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Re: Leave the pcv valve on or take it out pros and cons

Post by Basin_Runner355 » Tue Feb 06, 2018 5:47 am

Well two weeks ago i got in touch with a guy that suposed to know his shit has his own shop and does 90% airboat Work. He went through my carb and retuned it. While we were sitting there letting it run when i went get it it was still doing the same thing after idling for a few mins it starts to load up and puff smoke out the exhaust not bad but it’s smoke comming out he said it looked white to him. But it smelt more like gas he is the third person i brung it to. I haven’t got to go run it yet to see how it does but if it’s still not right idk who to go to next cause every mechanic does things a diffrent way and days the one before him don’t know anyting. Four ppl i know of bring theirs to the guy i brung it to this last final time hopefully. The problem i am having is i think it’s loasing up and when you go to start it sometimes it takes a while to start up again gota let it sit there and turn over
14ft diamond back mild zz4 355sbc pushin 450 hp 450 TQ 2:1 belt drive reduction with a 3 blade sensenich 78Jw series

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Re: Leave the pcv valve on or take it out pros and cons

Post by swamper2 » Tue Feb 06, 2018 8:46 am

make sure your rubber cap on the pvc tube at the base of the carb isn't cracked or rotten. If it leaks your carb will be difficult to tune. I put a 2 in piece 3/8 of rubber airhose with a bolt siliconed in it to replace the rubber cap.
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Re: Leave the pcv valve on or take it out pros and cons

Post by swamper2 » Tue Feb 06, 2018 8:47 am

make sure your rubber cap on the pvc tube at the base of the carb isn't cracked or rotten. If it leaks your carb will be difficult to tune. I put a 2 in piece 3/8 of rubber airhose with a bolt siliconed in it to replace the rubber cap.
16ft alumitech/406sbc/2.38w/3-80in.R's

SWAMPHUNTER45
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Re: Leave the pcv valve on or take it out pros and cons

Post by SWAMPHUNTER45 » Tue Feb 06, 2018 8:59 am

There have been several people who have been on Southern Airboat who suffered fatal lean conditions due to defective vacuum caps on their carburetor base.

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Re: Leave the pcv valve on or take it out pros and cons

Post by loudmouse » Tue Feb 06, 2018 9:01 am

If there was a vacuum leak the engine would be lean at idle not rich unless it was flooding
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:

Basin_Runner355
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Re: Leave the pcv valve on or take it out pros and cons

Post by Basin_Runner355 » Tue Feb 06, 2018 9:29 am

All my vacuum caps are good and brand new the carb was just rebuilt
14ft diamond back mild zz4 355sbc pushin 450 hp 450 TQ 2:1 belt drive reduction with a 3 blade sensenich 78Jw series

Basin_Runner355
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Re: Leave the pcv valve on or take it out pros and cons

Post by Basin_Runner355 » Tue Feb 06, 2018 9:33 am

I’ll take some pics today

Also the guy that put the Holley on put primary on the back side of the engine toward the distributor idk if that makes a difference or not.
14ft diamond back mild zz4 355sbc pushin 450 hp 450 TQ 2:1 belt drive reduction with a 3 blade sensenich 78Jw series

Basin_Runner355
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Re: Leave the pcv valve on or take it out pros and cons

Post by Basin_Runner355 » Tue Feb 06, 2018 9:34 am

Like i said it may be good now i haven’t ran it ima change my plugs also. So everything good and new
14ft diamond back mild zz4 355sbc pushin 450 hp 450 TQ 2:1 belt drive reduction with a 3 blade sensenich 78Jw series

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Re: Leave the pcv valve on or take it out pros and cons

Post by SWAMPHUNTER45 » Tue Feb 06, 2018 10:26 am

I was not implying HIS situation was a lean condition....anyways

Good luck with it

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