p c v valve

rep p c v valve

sorry for not enought enfo.these are std carb. new long blocks with edelbrock manifold and eldelbrock weber type 4bbl carbs.all new in 2005 the soot im talking about was on the top side of the choke plate.it was on the side close too where the hose goes too the flame aresta.and seemed to be oily.and that part of the aresta was kind of oily thats i was thinking pcv .also this soot took about 7 years to get there.i just went through the carbs set floats and new carb kits. so i am now thinking run it this season and see how much gets built up at the end of the year.some times i carry things too far boat ran for 7 years like that. thanksfor the help i learned a lot of the tech. points on p c v systems all the mercruser 5.7 never had p c v either i think ill put this too sleep for now.

 

It looks like you are right. Overflowing gas leave varnish and not an oily residue.

 

"also this soot took about 7 years to get there"

not anything to be concerned about then

How about blowby when running, does the engine produce a lot , moderate, little or none?
Blowby tells you a lot about the piston ring sealing.

I have twin IH 392 in my boat.
Years ago I got rid of the rotten broken 1970 contraption they called a PCV valve, and put automotive PCV valve, one for each valve cover. So it actually has 2 PCV valves. Been working fine for years. I never noticed any issues of blown seals or leaks which someone told me would happen. I just don't run the engines hard, I rarely run above 2000 rpm!

Another way which is the standard way, has

one PCV valve runs from valve cover to intake manifold vacuum.

one open 5/8 ID line runs from valve cover to exterior of flame arrestor.

Theory is I suppose, crankcase blowby air at low engine speeds when vacuum is higher goes into manifold from PCV.
Air at high engine speeds with little vacuum, crankcase blowby air goes into carb top by way of flame arrestor.

Some racers have put negative crankcase vacuum systems into engines, theory being less air means less windage on the crank, so more power at very high rpm.

 

There's a couple of ways to go about this. Racers evacuate crank case pressures, typically with a valve cover vent or a hose that dumps into the exhaust, which depressurizes the crank case. They're not really pulling a vacuum, which wouldn't be good, unless you owned an oil company, but admittedly some oil does get sucked into the exhaust. The other way is to use a PCV on one side of the engine, while the other uses a breather and/or hose to the flame arrestor. This works, but at high RPM you can get bank pressure differences, so an equalizer hose is rigged, between the two valve covers, with a "T" fitting and terminated again at the flame arrestor (or the exhaust).

Your duel PCV setup is essentially the same deal and an effective way, of handling crank case pressures and gasses. In all honesty, bank pressurization isn't a big problem on the usual V8 powered boat, producing less than 300 HP. Changes to this system, will make no performance improvements, though you might notice less oil from a valve cover breather, with a balanced or evacuated system, we're only talking about teaspoons of oil here and pressure imbalances are insignificant at these RPM and HP ranges.

An automotive approach will eventually solve these concerns, with an expansion tank and return line, permitting depressurization, leveling bank pressure imbalance and getting crank case gases reabsorbed by the lubricant or burned in the combustion chamber. Of course this in on an average engine. High performance engines need a different solution, but only to tweak the very last half a HP out of an engine.

 

I'll think you will find people do run lower than atmospheric pressure in the crankcase.
Each engine will have a sweet spot where the extra ring sealing helps horsepower
Plenty of dyno tests out there that say about 16" is best for power
http://www.429-460.com/t13910-moros...il-pressure-ect-very-interesting-check-it-out

 

I'm not arguing this fact, but the sample you've linked is a nearly 600 CID, 1,000 HP engine and though typical for a racer, not what you see in 99% of the V8 powered boats on the water. Even with the negative pressure provided by a pump, the 3% HP gain seen on this 1,000 HP motor, wouldn't be realized on the common 225 HP Vortec 350 often seen in production craft. Even it it was, we're only talking about 6 HP or so, which isn't enough to justify a $200 pump and $100 separator (I just opened the new JEG's catalog), not to mention the hoses (AN fittings?), etc. related to this type of upgrade. Of course you could Mickey Mouse the job with hardware store hoses and clamps, but it'll leak and rust.

Don't get me wrong, I'm all for free HP. I've just spec'd up a 750 HP big block and it has a vacuum pump a dry sump, separator, expansion tank and all, but again, someone with a Mercruiser, Volvo, Crusader or whatever, doesn't need to think along these lines, just a clean return and blow by bleed off, that doesn't leave oil all over the valve covers.

 

yes all true Par, its not a solution for a production boat.