One of the 502 MPIs in my 311 is missing the vent tube that goes from the flame arrestor to the valve cover. The mechanics (if you can call them that... a comedy of errors on this one) lost the tube. I'm going to replace it with some fuel hose, but I need to know the sizes (I'm thinking 3/8 at the arrestor) particularly the diameter of the breather grommet on the valve cover. I'm. It at the boat, and will be picking up some parts this afternoon. A search hasn't come up with anything.

Thanks!
-Tom

Tom, my 454 Carb'ed is 1/2" at the arrestor. PM me with your # and I can measure what you want. Good luck

Grommet going into valve cover is GM# 3989347 (verified by my 454 Carb'ed #)
BRAND NEW GENUINE GM OEM PCV VALVE GROMMET #3989347

Thanks!!

here bigger is better...