I have some blow by on one of the 440s in my boat. The problem engine is leaving an oil mess (not that bad) around the breather cap as well as around the bell horn of my AFB.

My question is in regards to my PCV/breather cap set up. My breather cap has the tube connected to the air cleaner. My understanding is for the tube to pull air into the engine. It seems that the carb is competing for air with the breather cap tube. Is the engine able to pull enough air? Would I be helping the cranckcase pressure by eliminating the tube going to the carb and let the breather cap pull ambient air rather than air being sucked into the carb?

Thanks!

 

bush -

As long the the PCV and and breather aren't in the same valve cover it really shouldn't matter all that much. (The PVC needs to be connected to a full manifold vacuum and the breather is passive; theoretically allowing air in or out - typically in on a PCV system, letting air in, but it can work either way.)

If your PCV valve is working and you're still getting increased crankcase pressure, there's something going on internally that's going to need addressing sooner or later.

Archer

 

Thanks for the reply. Yes, PCV is on opposing side and I routinely check to hear the internal rattle inside the PCV.

UGH...

 

Most marie engines did not use a PVC valve, They used a breather on each valve cover and a hose from the breather to the air cleaner.. A factory marine carb and intake do not have Vacuum ports.. This is for fire reasons, from back firing threw the carb. It is US coast guard rules.. I messed on speed boats for years.

 

I reserve the right to be wrong, but they do need the PCV so the crankcase fumes can be reburned rather than venting inside the bilge, so the marine carb does have the intake port. Carter AFBs (marinized) do. The new Edelbrocks don't come with them but are being ported by the new owners. The air cleaner is strictly marine to restrict the back-fire, rather than a paper one. The distributor does not have a vacuum port either. Love spending more money on all things "marine." 'Break Out Another Thousand."

I am cleaning out the breather caps with cleaner in hopes of helping it breath a little better? Anything to relieve some of that pressure.

 

what weight of oil are you using?

 

I run 15/50 syn in my boat 514 ci.. Here is a little trick for the messy breather caps. fold a paper towel up and put under them.. The blue heavy duty paper towels from auto zone work best.

 

I use Rotella 15/40. I'm thinking about also adding a zinc additive this year.

 

If you run it hard, such as in poker runs or fun runs I would go to full syn.. Its does not thin down like non syn. oil. Most performance boaters are running the 15/50 for this reason. A boat engine is built with looser tolerances. I tried a non syn. oil and after a hard run at idle it would drop 7-8 psi and at 6000rpms it was also down about the same. I do not run syn. oil in anything else just the boat. If you have a roller motor no need for the additive.