View Full Version : Valve Cover Breather Options

05-06-2005, 08:08 AM
Twin 502's leak oil out valve covers when under heavy load (boat is very heavy so most runs over 3500 rpm). Today I have the rubber gromet to a hose to the spark arrestor setup. This picture is with the hoses removed... What do you have? Does it work? Where can I buy it?


05-06-2005, 08:32 AM
K&N makes the adapters for their arrestors/filters. The illustration is on page 4, of the 2002 K&N marine catalog.

2.75" height, 5/8 hose is #85-1362
4.0" height, 5/8 hose is #85-1462
6.0" height, 5/8 hose is #85-1662

they are also available for 1/4, 3/8, 1/2, 3/4 hose as well, but 5/8 seems most common

you will need TWO adapters per engine

call Humberto to order 305.593.6160


05-07-2005, 12:59 PM
If you look at most carbureted marine setups they all have the hoses to suck the vapor out, question is where does the air come in to allow the air motion. Yeah they put a PCV valve on one and leave the other open, joke no air flow. All they really do is catch the blow by vapors, adding intake vents on the valve covers is the only way to get the flow needed. That is something I was planning on doing one afternoon but got foiled by the Dart heads, Dart raised the rails to give more rocker clearance which after the headers were on I noticed do not allow me to pull the covers without pulling the headers. Now it has turned into a rainy day project, I plan on using the type pictured below.


Moody Blu'
06-14-2005, 01:05 AM
so do you actually need a pcv valve? i was thinking about this and im not sure what they really do? i have a pcv valve on one side and a breather on the other. how does this actually work? there is a place for a hose to be connected on the top left side of my new carb, can i connect the pcv valve to it? heres a pic.


so should i just connect the pcv to the spicket on the carb or whatever thoe fuel connectors are called? im drawing a blank..Right now i just have a hose on it and its blakced with a screw


06-14-2005, 01:31 PM
Ditto on what Jim said. I have the K&N set up and have had no issues, a clean engine is a happy engine :biggrin: .


06-14-2005, 03:35 PM
I have converted my last two boats to a PCV system such as a car just converted two more engines in my latest boat. They have worked great so far. No oil anywere on engines.

06-14-2005, 03:36 PM
Moody plug that into your carb.

06-14-2005, 08:26 PM
Broque the PCV normally comes off a plate under the carb, I have that plate of a 5.0 Mustang a buddy had it is sitting on my bench. I went another way, on my stbd. valve cover I installed one of the large round vents with the filter inside where the hose going to the carb would normally be hooked up. On the port side I made a Y and added another carb intake fitting right next to the existing one so I now have two hoses to the carb, I made up a small plate that fit around the two carb intakes to try to increase the flow to those hoses. I can hold a cigarette by the filter at 1500 RPM and watch the filter suck the smoke in so I am absolutely sure I now have good air circulation through the engine. You know about how long I was on the wrenches, it has always amazed me that the marine industry did not come up with a good air flow system, fact moisture is the worst thing inside an engine. Honest I would say the 60-70 percent of the oil caps I have opened over the years had white muck inside, the standard two hoses to the carb do -0- just think for a minute they are suppose to draw vapors from the engine into the carb. OK now where does the air come from there is no breather so it is really a no brainer that the system can not and does not work. The only thing they do ingest is blow by! One of the very best systems ever was on the older Chevy V8 motors, they had horse hair filters on the valve covers and a pipe coming of the back of the intake manifold that extended down behind the engine to have the vapors sucked out by the air rushing by at speed. When you opened one of them up they had -0- signs of any moisture! The Society of Auto Engineers clearly states moisture deteriorates the oil and aids in the destruction of the engine. I feel that everyone should do their level bast to vent their crank cases better!


06-14-2005, 08:41 PM
Phil,could ya post some pics of this set-up of yours...TIA

06-14-2005, 09:45 PM
Hope the pic shows, this is my experimental setup. As I mentioned in the first post due to the high rails on the Dart heads I am putting off installing the the vents pictured in the first post until I pull the headers which may not be untill fall. If the pic does come out you can see the chrome air breather on one valve cover and my HOKEY Y fitting to pipe two tubes together trying fo a little more flow. When I finally do pull the headers I will install a vent on each valve cover and go back to one hose off each vavle cover, for now what I slapped together will have to do I am OK with it because I know it does draw air through.


06-15-2005, 07:40 AM
The ulimate system is combining an extractor system with a PCV system. Several boaters have added an extractor system. The next step is to add one of the vacuum pumps racers use these days.