318 Vapor Lock

Tech Question

 

Dennis Bartnik, Red Lion PA, 1985 Dodge D150 1/2 ton 318

I have a stock 318, 2bbl carb, Holley electric fuel pump,with regulator valve set anywhere from 2 to 5 1/2 PSI and still it “vaporlocks” constantly. Why?

 

Dennis-

Because the Holley pump does not have enough line pressure to preventboiling in the lines with today’s “gas”. Could even be boiling upstream ofthe pump! You need at least 30 PSI before the reg, and non-diaphgram typeregulator (Mallory, etc.). Bosch pumps seem best. Reg should be as close tocarb as possible.You also need a return line (with metered orifice, about 0.050″) AFTER thereg. (closer to carb, the better).And you need a carb thermal spacer.And you need fuel lines insulated or routed away from heat.Best suggestion: in-tank pump (get one from ’92-93 318 or ’93 360 pickuptruck, tank and all.)

Rick

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