I was thinking exactly what you said about the intakes .I just changed the intakes and the old aluminum ones were rotted on the water ports by the head.. I haven't taken the boat out for a good run yet...Hopefully that was the main problem..

Same thing. Both are essentially pulling a vacuum on the breather line. Only difference with the pcv, is you will be building pressure in the crankcase to whatever the pressure is on the pcv before it pops and let's the pressure by. If you just had hollow plastic elbows in the valve cover before, i don't see how a pcv valve would make any benefit to reducing condensation. Bottom line, the engine has to breathe.

I used to have pcv's on these engines with the old carbs.. Then i had Nickerson performance build me some new holleys 960 cfm Dp carbs.. These did not have a port on the baseplate of the carb for pcv's like the old ones did
I agree with what you saying about ( same thing)..except I think its more efficient for the pcv to be connected directly to the intake or carb. The other side of the engine has a plastic elbow in the valve cover and a 5/8 " hose connects to a tab mounted on the flame arrester..How much suction is actually pulling from that hose which sits 1/4" to a 1/2" away from the arrester and has the rest of the arrester open to the engine conpartments free air.. In my opinion (not much) At least with the pcv directly connected its definately pulling from the valve cover, crankcase, etc

It should be the sandwich style that is between the filter and the pad.

There is no positive flow with the elbows only. PCV is a Positive flow, as in the name. The turns of air within the engine is much higher with a pcv valve, hence the moisture is removed.

BT :cool:

I found this information

The Pcv valve is metered to allow a certain flow in accordance to the blowby (usually calculated by displacement and compression) generated by the engine over most of the rpm range.
It allways sucks. The only time it doesn't is if there is a backfire and then it acts like a check valve preventing gases from the intake from going into the crankcase.
Because it always sucks, it is also designed to meter the flow according to the engine demands at different rpm, at the same time hopefully removing the blowby vapors, but yet not sucking so much as to pull oil into the intake.

At idle (high vacuum) the tapered metering valve is pulled to the right into the seat restricting the amount of vapor pulled.
At WOT (low vacuum) the tapered metering valve is at the left allowing a full flow.
At cruise or light load the valve is to the right being restrictive, but to a lesser degree than idle.
It also varies under different load conditions just as the intake vacuum does and meters the vapors according to that vacuum and also the amount of blowby produced.
There is also a saftey net built into the system. Under extreme rpm or loads. the fresh air intake tube acts as a crude but temporary breather when the blowby pressures overcome the pcv negative pressure (for various reasons) and allow the blowby gases to go up the tube thru a small filter and be reintrudiced thru the carb for reburning. Some of the oil condenses before the small filter and some ends up puddling in the bottom of the air filter housing in a more sever case. When the excessive blowby returns to normal the pcv valve takes over again. I'm sure you've seen it in worn out engines.

As you can see, it is not just a PCV valve, but a precise metering valve that is matched closely to your specific engine.

Since the conversion from the draft tube system to the closed pcv system, there has been a remarkable decrease in the creamy foam found in engines and more importantly, failures from sludge (results of acidic vapors and moisture) buildup.

rssteiny, what was your problem with milky oil and how did you fix it.


35fountain, i just had new valve springs put on my 500HP's and now I have milky oil on dipstick and under valve covers and didnt have that problem prior to that work. Comp test shows good, pressure test manifolds shows good...I have no idea what to do.. sounds like i may have the same problem you have, but dont' understand why it didnt do it before and now it does.. Dont know which way to turn...

Have not fixed it yet, same for me prior to redoing the heads port work and all new valve train, and cams, lifters , chain gears, last winter,never had the problem this past summer it was there just in oil cap holes and breather hoses to flame arrester, nothing on dip stick or in oil. I think my problem is my motors never get above 190 oil temp and is not hot enough to cook out the condensation.

Where is the oil t stats on the 500 hp carb motors and can they be changed.

The oil thermostats are inside the square mounting where your oil filter is..your oil hoses are also there, Should be 4 hoses....My engines are not 500's they are 509 gen IV..I do not have oil thermostats.. My oil temp is above 200 cruising and higher at wot

I won't know if my problem is fixed until I go for a ride..When I first got my boat it had PCV's.. I removed them and ran 2 hoses from the valve cover to the arrester's..Now I put back the pcv's..Everything else checks out.. I never had milky oil on my dipstick, only under the valve covers
Did you change anything...The Hp500 has a pcv at the base of the intake behind the carb.Does yours have pcv's ??..Did they remove your heads? to change the springs..Head gasket ??