Modify Cutlass for modern gas (vapor lock problem)

[Stepas]

I have a stock 1971 Cutlass Supreme, 350 2bbl, automatic, that is recently giving me fits with vapor locking in the past 4 years or so. For this reason it hasn't been driven much at all. I looked into the problem and realize the fuel system must be modified with a return line. My car does not have one presently. Bending a new articulated line looks like it would be a real pain to accomplish. My question is, can use the vapor return line for this purpose? What have you guys done? I already dropped the tank and I will buy a new fuel sender with the second line.

 

[Rocketman269V]

Have you tried buying Rec 90 fuel, which doesn't contain alcohol?

 

[Stepas]

It's not the alcohol, nor the octane that is the problem. The problem is that modern gasoline has more volatiles in it than in decades past. They leave the volatiles in today's modern gasoline because nearly all automobiles are fuel injected. The gasoline stays under pressure from the tank to the point it is sprayed from the injectors. My car uses a fuel pump that sucks the fuel from the tank, meaning it is slightly under a vacuum. It is prone to vapor lock, which now happens with regular occurrence. Also, other Cutlass models from 1971 have a return line originally designed into the vehicle to combat vapor lock. Those are chiefly the bigger block engines or 4-bbl carbureted engines. Mine doesn't have the return line.

 

[Rocketman269V]

You could also try installing a small pulse type electric fuel pump back by the gas tank. This will put a positive pressure going to your mechanical pump, rather than a vacuum. I did this on my '78 Chevy Silverado, which had a 350 Olds gas engine, and it cured an issue that I was having when towing my race car on a hot South Florida day.