Heat & Vapor Lock Time of The Year Help..

[ski4funn]

Hey Folks. Hopes everyone is enjoying a trouble free year so far.. My good old '77 240 is not enjoying the heat.. I have a GM350 engine w/a edelbrock 4 bbl. carb. The carb does have the 1/2 riser to get it directly away from the engine. I have 2 louver vents; each on has two 3" vent lines feeding the engine compartment & I have two bilge blowers putting out 175 cfm each to help remove engine heat. I am still having vapor lock issues after sitting idel or I shut the engine off for awhile. When I restart the engine or resume running the engine will sputter and act up @ WOT so I have to back the throttle down. If I remove the engine cover and run the boat with fresh air flowing around the engine, the problem goes away and she runs great. Any ideas to help with the problem without trying to install more vent holes?? Thanks for all your ideas and help folks.
Lance

 

[SCORPIO]

How hot is the engine running, what temp do you see? Could your risers/manifolds need replacing? If they are cloged, you could be getting higer engine compartment temps from the overheated metal. You shouldn't need any more vents. Could you relocate your fuel line further from the engine to increase the airspace between the line and the hot engine.

 

[ski4funn]

The engine temp is only running 125 while running. The engine is not experiencing over heating, it is just when I sit for an extended period at idel or shut the engine off, which in turn develops "heat soak". Yes, I could mover the fuel line from mechanical fuel pump to the carb. further away from the engine, but I think additional ventilation is required... As I stated, when I removed the engine cover and allow the engine to be exposed to large quanities of ambient air, it runs fine. Again, this only happens on hot day 90+ degrees...