Crankcase ventilation and flame arrestor questions

[bob smith]

My current set-up has a vent line from each valve cover to the flame arrestor. Can I eliminate this ? (new valve covers aren't drilled for the vent hose).
Is a flame arrestor required if the carb intake is plombed directly (w/metal ducting) to an outside vent?
Thanks for your input.
Bob Smith
Chester, SC

PS: no comments on "The Epiphany"???

[jamundsen]

I liked your idea of modifying the "donor" boat. The flame arrestor is required equip. The vent lines are for EPA so the excess smoke, fumes get recycled back thru the carb. I suspect you could lose them.

[Nova SS]

FWIW, you have to have the crankcase vented somehow or you will end up with leaks. I would have a breather on one valve cover(to allow fresh air to enter the motor) and a PCV valve, with a hose leading to the intake manifold/carb/or flame arrestor assembly, on the other valve cover to allow gasses to escape the motor. Running without a way to vent the crankcase will, as I said already, cause leaks as the pressure builds up in the motor especially on longer runs. (fixing the leak will be a PITA once the motor is in the boat)

[jenko]

agree with nova ss.
I would drill hole in inlet manifold (rear to crankcase) and vent to carb ( atmosphere side )then drill front for pcv valve and conect to 3/8th vacuum port at base of carb assume this is v8 with rochester or holley

[bob smith]

Thanks for the input.
I've decided to drill the new valve covers (there is a boss for the hole) and reinstal the original hoses that vent to the flame arrestor.
I'm running an Eldelbrock (AFB) 750cfm carb, Any suggestions for a flame aresstor that will support that flow? The one I have seems awful small.
Bob Smith

[bob smith]

Where's spellcheck when you need it!!!

[TUGMYWAY]

Is the carb , USCG ?
All ports must be spark baffeled. A backfire could blow off a hose and set a motor compartment on fire.That is if it has fumes.That is why most venting is at the flame arrestor.
Every thing needs to be USCG.

Their are lots of oversized flame arrestors.All USCG.

http://www.summitracing.com/parts/KNN-59-1195/

[bob smith]

All is USCG compliant, the Carb is an Edlelbrock 1410 marine version. The venting is OEM Merc. Thanks for the Summit tip.
Bob Smith

[Caber-Feidh]

I use the tiny little 6" mallory on 80532 alky-conversion dominators, and never felt they weren't breathing well. (Shhh... don't tell anyone they aren't marine rated! with high volume pumping capacity, if the floats stick, it's gonna be squirting E-85 and methanol mix all over the place, regardless if it's marine rated.)

As far as positive crankcase vents go, unless your carb is one of the "off highway", or rather ancient, it is an emission calibrated carb, and is needs the added air flow to correctly balance. The carb was built for the addition of unmetered airflow from both a PCV, and EGR systems coming into the intake stream below the carb... NOT above it in the airhorn. Eliminating either will require rejetting, and may require a bit of rework on the transfer ports. Best bet is to just put them on in the correct places for the setup on your carb.

EFI will require a high level remap to run right with them gone.

[bob smith]

I got a K&N Marine Rated Flame Arrestor that their Tech Services said was good to over 850cfm. The Edelbrock 1410 is rated at 750cfm.
I'm joining the "Better Breathing Club".
Re the crankcase venting, the only port on the 1410 is at the air horn and is for venting the fuel pump. I'm going to run the vent hoses from the valve covers to fittings (available from K&N) on the exterior of the filter.
Bob Smith

[Nova SS]

your carb only has one port and its for venting the fuel pump? Are you planning on vacuum advance for your distributor? Cause if you are your going to need a port on the carb for that as well.(below the throttle plates) You might need to get a spacer plate that goes between the carb and intake manifold. You can add ports in this to attach various things to that should have manifold vacuum to run correctly like your distributor and PVC, etc. Of course a spacer plate will raise up your carb so that might create clearance issues.

[bob smith]

Old School
No vacuum advance, no pcv.Max Vac!
Been running this way since 1975.
Upgraded to Mallory HEI 3 years ago from a Mallory dual point set-up. (Points wouldn't last a season).

Bob Smith