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View Full Version : need some help from the late model SBC/Merc guys



gold-n-rod
04-30-2007, 08:33 PM
I have my 5.0 SBC w/mpi in a few pieces to install the GLMs I bought from Don last year. Here is my mystery.....

On the starboard side, the valve cover is vented, using rubber hose, up to a fitting in the intake, just behind the throttle body.

The port side, strangely, has a piece of ribbed plastic tube (like you'd wrap wires in) that runs forward between the cover and the exhaust manifold and is connected to ................. nothing. That's right, either it vents the port valve cover to the bilge or it serves as an intake of air via the cover.

I think this is odd since anything I've ever seen (since the road tubes of the 50's) vents the valve covers up to where the fumes can be captured and burned.

Anyone want to weigh in here? Or, better yet, anyone have a manual with an exploded view of the top of the motor?

Thanks in advance!

rustnrot
04-30-2007, 09:09 PM
Its a breather tube and should connect or clip onto the spark arrestor in some way.

gold-n-rod
04-30-2007, 09:15 PM
Its a breather tube and should connect or clip onto the spark arrestor in some way.

I agree, but why isn't it rubber like the other side and plumbed to the manifold? There are no empty fitting on the spark arrestor or throttle body.

rustnrot
04-30-2007, 09:18 PM
Are you sure there isn't a plastic fitting on top of a plastic cap that fits over the top of the spark arrestor? I had a 4.3L MPI with that configuration. Mine had the corrugated plastic wire conduit for both sides.

gold-n-rod
04-30-2007, 09:32 PM
Are you sure there isn't a plastic fitting on top of a plastic cap that fits over the top of the spark arrestor? I had a 4.3L MPI with that configuration. Mine had the corrugated plastic wire conduit for both sides.

Not that I could see, but I'll look again this weekend. Thaks for the reply! :wink:

Ranman
05-01-2007, 08:11 AM
MErc likes to use a non-slit version of the ribbed plastic as vent tubing. I have the same material on my 350MAG going from my valve cover to my flame arrestor.

mrfixxall
05-01-2007, 10:37 AM
ive seen this too, because it is plumed into the back of the intake it creats alot of vacume in the engine which sucks alot of your crankcase pressure out..Its just a vent tube and does nothing but let the air into the engine so the other tube going to the back of the intake can suck all of the pcv out and not suck the gasgets out if the engine at the higher rpms...

gold-n-rod
05-01-2007, 12:19 PM
ive seen this too, because it is plumed into the back of the intake it creats alot of vacume in the engine which sucks alot of your crankcase pressure out..Its just a vent tube and does nothing but let the air into the engine so the other tube going to the back of the intake can suck all of the pcv out and not suck the gasgets out if the engine at the higher rpms...

This makes a lot of sense to me. Especially since the starboard cover is directly vented to the manifold, not just attached to the flame arrestor. All that vacuum needs to come from somewhere and your suggestion is very plausible. Thanks!