Well I got a 1968 with 350/350 setup and last summer I could get 23 miles to the gallon, but now in town I get less the ten. I got new plugs in and checked the manifold for leaks but nothing. It runs fine but gas is getting expensive. The car is very stock with only Edelbrock manifold, and a Holly 400 CFM Carb. So what is wrong or is this normal?

Check this forum.. seems to happen commonly and this could be your problem.. A new aftermarket distributor could help with gas mileage too

http://www.elcaminocentral.com/modules.php?name=Forums&file=viewtopic&t=2709

WROR

I would check the basics.

1. Air Filter
2. Points, Cap, rotor, condensor
3. Plugs (are they burning nicely?)
4. Wires (check and replace if necessary)
5. Timing
6. Vacuum gauge adjustment/setup of the carb


Start simple, then go from there. Something has cause a 13mpg loss, that is A LOT! I do however have to question the fact that you got 23 miles to the gallon in town with a carburated 350. If you did, that thing must have been tuned to the hilt. Either way, look into the basic suggestions, above and go from there. Chances are you'll find some more MPG and power.

Its not the timing, and the plugs look good. I was getting 23 MPG highway and 18 in town but that is still a good drop. The carb is not leaking but I was wondering if the power valve is blow. How do I test the power valve on a Holly carb?

Not to mininize that their still mught be a problem but during the winter your gas mileage is going to drop. Warming up the car & different formulation of gas makes a difference.