p c v valve

5.7 chevy motors long blocks with edelbrock man. i seem to be getting a lot of sooton choke plate.from hose from valve cover these motors have about 60 hours on them.i am wondering why i cant hook up a pcv system like a car? so it gos into man. and does anybody know why they dont have a pcv on boat engs. thanks

 

They all used to have PCVs. They stopped sometime in the 80s. You can install one, but have to re-jet the carburetor.

 

I thought most boats do have them, they may be more primative than on modern cars, a newer system can certainly be fit to your boat. By the sounds of it your engine was heavily alterted perhaps by a previous owner, so no telling if what you have is the correct installation. A pvc system improves the economy of the engine and prolongs oil life by venting any combustion blow-by out of the crankcase. It also lowers emissions out put since the blow-by is cycled though the engine rather than vented to the atmosphere.

Hot rod shops sell oil traps for the PVC system, I would consider one of those for your boat. It is a chamber that goes on the hose between the PVC valve and the intake manifold, it traps any oil droplets and vapor into a chamber. Good luck.

 

Most carbureted boats have two hoses that end somewhat close to the spark arrestor.

 

looks like this:

 

Newer engines have PCV, but it's electronically controlled and often not in it's usual location on the valve cover. These systems now incorporate a fluid regulator, a contaminate trap and possibly other bits and additional plumbing to get pretty precise about the use of crankcase gases.

Which engine do you have? Is it a CFI or SFI Vortec 5.7? 350's prior to the CFI 5.7 (early 90's) wouldn't have the Vortec heads and would have a normal, PCV on the valve cover.

If you're getting soot, you're probably experiencing intake contamination (blow back) and this can be handled a few different ways, but a plugged PCV is the first place to look, unless you're also blowing blue smoke from the exhaust.

 

Why rejet the carburater its only letting air in when its pressurized from blow by inside the motor !!! the inside of the intake manifold gets really grotty over time depending where the hose from the valve hose enters the manifold !!

 

That is not how a PCV works. It allows full flow at about 1/3 throttle opening, which is a vacuum leak. The PCV leans the mixture, so jets have to be adjusted for optimum performance.

 

again this is in a boat two chev 5.7 witch runs about 3000rpm most of the time. so i see where jetting could be and issue.starting to run too lean?boat runs great so mabe ill pt up with the soot?and just clean it from time to time any more ideas/thanks for all the help

 

You could add an oil trap to the vents. Either way you'll need to clean them once in a while though.

 

If you have soot on the choke plate, you're way rich, not lean. Getting carbon this far up in the intake tract, suggests something a lot more concerning than a need for PCV.

Again, what "generation" small block are you running (just provide the year), is it carbureted or FI and if injected, which type CFI (throttle body) or SFI (direct port injectors)? Does the word Vortec appear on the engine anywhere?

 

An overflowing carburetor may do that too. When you stop the engine fuel falls into the manifold and the fumes coat the inside of throats and the plates with a brown/black gunk. The exhaust crossover is right under and hot enough to boil the gas.

 

Agreed, there's more going on and a simple inspection by someone with some skills might be the best advice. I can think a quite a few different things that could be happening, from a sticky float needle to a cracked manifold, with all sorts of stuff in between. Since it has the aftermarket intake on it, the two piece SFI Vortec manifold, which is known to offer problems, can't be to blame, but it would be nice to know which 350 it is.

 

vacuum is so low the pcv will spend its time shut in a typical boat that why they dont have them.
Plug your vacuum gauge into a boat engine and go for a drive, its a little bit different than a car
Now they are required to have them they need electronic controls

 

A PCV is closed at high vacuum (idle) an opens at usually 10 PSI or so and then has full flow. At idle the typical vacuum for an engine with no emission controls is 14 PSI. It will get 10 PSI at about 1/3 throttle. The PCV has a ball and a spring. Vacuum closes the ball against the spring pressure. As soon as the vacuum drops, the spring tension pushes the ball away from the seat and opens the valve.