If the vacuum at idle is too low (from your cam) then the power valve can be opening too soon - Check the amount of vacuum at an idle then get a power valve that is 1/2 that vacuum. (12" Hg should use a 6.5" power valve (marked 65).

 

Yep, went to a 160 and changed back to a 185. Hwy mileage cut in half with the 160deg. No problems now.

 

Not sure how to check the vacuum secondaries to see if they're engaging too quickly...never had to deal with. My neighbor with the '67 coupe did have a problem with them engaging too early and had to adjust.

 

Would a low vacuum with the power valve opening too soon explain why the engine rpms drops lower than it should, to the point of almost killing the engine, when I go from no load/park/neutral to a load/drive/reverse? Or is that part of my underlining problem with the poor gas mileage? Because no matter how much I play with the dizy and carb the most vacuum I can get out of the engine is around 14Hg but that is with incredibly advanced base timing (16ish). I will double check my vacuum and let you know.

Given the thermostat I have is the one I had before this problem developed so I won't worry about changing it out.

When I looked at the spark plug I only looked at the ceramic section and it was a medium to dark brown not the ideal light tan and I didn't pay attention to the rim of metal, but it wouldn't surprise me if it was black because I am sure not pissing the gas on the ground.

The carb I got was non adjustable float level carb so I won't be able to tweak that without truely modifying the carb. The carb is Holly's basic single pump 600cfm, four barrel, vacuum secondaries, and electric choke.

With the weekend almost here I will have time to get in and work on it some. I should be able to get some more info on the problem, hopefully fixing it, and give you guys and update. Thanks

 

so if im reading this thread right then a 160 stat is junk? if im seeing it right then sunday im switching mine cuz thats what i got in mine and i use a tank of fuel in 198 miles lol and mine is bone stock

 

You are correct, sir, you'll get less sludge in the oil, your heater will work better, you'll have a bit more power, and you'll see at least a slight increase above 12 mpg.

 

Update:
Reset dizy to 12 base timing with the mechanical advance taking it to 30. The vacuum advance adds another 20.
Reset the idle mixture screws and could only get 14 on the vacuum gauge.
Fuel pressure was sitting slightly above 8
With these factors and knowing the engine is running rich I am headed to go pick up a fuel regulator and power valve and then I will go from there.
Thanks for the help so far guys.

 

correction, I am not changing my power valve. I just looked up my carb and it already has a 65 power valve. With the 14psi I am pulling on vacuum my engine is sitting between the 65 and 75 power valves and I figured if gas consumption is my problem then running a little lean on the power valve will be fine. Time to get a regulator.

 

yes, set the regulator to about 6 or 6.5 psi. Once you did that you _have to_ adjust the float levels. ask for instructions if unsure. if you ended up resetting curb idle, you have to adjust accellerator pump as well

 

The carb I bought specifically indicated it was nonadjustable on float levels. Do you suggest that I go against the manufacture and change them anyway? http://www.summitracing.com/parts/HLY-0-80457S/

After installing the pressure regulator I was sure to reset the idle mixture and idle speed. I did not adjust the accelerator pump but will do that before I take it out next time around.

The regulator is in and working. The car seems to run more smooth than before however I have not taken it for a long enough drive to figure out its gas consumption.