Hot car, hot humid day, performance problem
 

I was out Woodward last night in my 80. The day was about 85* and humid. My car has a 180 t-stat and a lighter weight fan (not a clutch fan).

I sat idling waiting at the drive-thru for food for about 3-5 minutes. As I took off, I tried to accelerate. After about 2000 rpms, the car started chugging and sputtering (almost like if you try to drive with your choke shut).

I could see fuel boiling in my fuel filter when I finally parked a few mins afterwards.

I have a 10" Chrome air cleaner on the car with an open shaker scoop mounted to the hood. No heater/ac. Car has a 68 400 with 69 #62 heads. Again, 180* Thermostat.

What would be my best course of action to prevent this from happening? Aluminum radiator to dissipate heat (such as a BeCool)? Electric fuel pump acting as a pusher for more liquid fuel (presuming that my fuel was turning into vapor when the issue occurred)? An electric fan in conjunction w/my current fan? (If so, what cfm/size is recommended?)

Vapor lock..........common, especially with todays fuels.........

Running a good un-oxygenated fuel or a race gas/9x combo of fuel may minimize it......eliminating the mech. fuel pump and using an Electric at the tank with a return line may minimize it.......running a Cool can to keep your fuel temps a little cooler may minimize it......insulating your fuel lines may minimize it.......


Notice the word MINIMIZE..........you may never cure it completely.....clear that hot fuel from the carb after idling for long periods by reving the engine a couple times...........

yea id try to insulate it first and see if that cures it, if not id suggest a return style fuel system with an electric pump

Make sure your fuel line isn't touching the block anywhere, Re-route it if it is. Insulate the fuel line would be the step after that.

Thanks for the replies. What fuel pump should I get? I have a Holley 750 w/vacuum secondaries. Can someone give me a good recommendation for an electric fuel pump? I also have a plugged fuel tank vent line (and no charcoal cannister). I've got to look into this issue. Right now, I took the gasket off my gas cap to vent the tank. I guess the elec pump will be my excuse to work on the fuel lines. Now, I should run the electric pump in PLACE of the mech, right? Thus I'd buy a blockoff for the mechanical pump, and then install the electric?

Also, revving the motor didn't help yesterday -- it was THAT bad :( It was only bad under a load, however.

I'll be running straight (or mostly straight) leaded 110 octane in the car to try to help also. It seems to be a lot worse on straight 92 octane unleaded....so w/my CR, I'll run 110 to help.

Thanks again. I had a feeling it was vapor lock. I'll also try insulating the fuel lines...but will probably start w/an electric pump as soon as I get a good recommendation.

Thanks again!

Good suggestions by others. The manifold sits reeaal close to the Holley float bowls, feeding heat into the bowls/fuel. You could try a phenolic spacer, [ either a 2 or 4 hole to retain the manifold characteristics ] under the carb 1/4" to 1" thick, thicker being better.

I've got to play with air cleaners then. My 10" round just fits inside my shaker. Being a 68 motor, the adapters the previous owner used to install the motor put the motor offset to the passenger's side somewhat -- thus my air cleaner sits inside the scoop very close to the right-most edge. If I can get a spacer between the carb and intake, it'll have to be very very short, which probably won't help me that much.

But I'll definitely take these all into consideration.

Which electric fuel pump should I buy? I was looking at the Holley Blue pump. Also, would I be able to run it in tandem with my mechanical? I know some guys do this, and I'm curious the difference between going all electric versus installing an electric pusher/helper.

I had the vapor lock type problem on my 455 in my 65 GTO and I was running both mechanical and an electric pump and a 750 Holley. We found that the mechanical pump was getting very hot and added to the vapor lock problem so we eliminated the mechanical pump and that helped. Make sure you have at least 3/8 inch or 1/2 fuel line from the tank to the front. An aluminum radiator would help. I bought one of Summit's universal GM aluminum radiators and that dropped my temp by 30 degrees but temp will creep up to about 220 when in traffic and the weather is hot. My 455 has never liked a thermostat so I do not run one. In the summer I run straight water with a water pump lube.