Hey guys i have my carb all tuned up and it doesnt't smell and no black smoke, no flat spots, its all good. But i seem to be getting between 5-7 mpg driving around normal, now i know this isn;t right. What Rpm does my secondaries open?? there mechanical. Also what else coudl be the problem? I have bad valve guides and i know theres carbon buildup on the valves but can that make it that bad??

 

Your secondaries open up based on flow demand, not RPMs. They're not really "mechanical", either, in the normal use of the term (the throttle blades are opened mechanically, but the air flow through the secondaries is controlled by weighted air flaps).

What do your plugs look like? Do you have the vacuum advance hooked up? Is your odometer working correctly?

 

last time i checked my plugs looked pretty normal, a little oil on them from the guides being bad, yea i have a summit Hei dist. I have the vacum advance hooked to the times vacum port on the carb. On an edelbrock its the little one on the passenger side correct?

 

Yes it's on the passenger side.

"comp cams 230/230 duration- 480/480 lift" = your gas mileage problem.

 

There's got to be something majorly wrong if the fuel consumption is really as bad as you say. You should be getting 2 or 3 times the mileage you claim, even with the relatively hot 230/230 camshaft. If the engine isn't running really rich the fuel must be leaking somewhere.

The worn guides won't be helping the engine's efficiency but again, I can't see them accounting for it eating fuel like you say.

Is it making good power and running at proper operating temperature? If the engine feels strong then I would be looking for a leak in the tank, lines, filters. Does the engine oil on the dipstick smell like fuel? A mechanical fuel pump could possibly have a porous diaphragm and fuel would be dumping into the crankcase.

That's all I can think of... What are your actual numbers for fuel consumed & miles travelled?

 

Do you think there is a cam i could buy that would make the same power and give me better gas milage?? I am probably going to get a set of vortec heads machined for high lift cams in the near future. Do you think with vortec heads, performer rpm vortec intake, and my 750 carb with a diff cam i could get into the 12's and have better gas milage then i do now?? I was thinking about some 3.73's down the road also

 

if i baby the car i can get about 30 miles out of a 1/4 of a tank

 

well there is your problem...the gas guages on our cars are extremely inaccurate. when i fill the gas tank up the needle wont move off of full for like 5 days of driving hard, but when it starts to move, i try to find a gas station. our tanks are V shaped. at 1/4 of a tank of gas on your gauge...you probably have like 1.5 gallons left. you are getting 15+ mpg...which isnt the best ive seen for babing it...but better than you descibe.

 

Here is something you can try to help acceleration and may improve the gas mileage.

Remove the cap and rotor from the distributor.
remove the advance springs and weights.

notice the you can rotate the advance mechanism now.

get two medium sized plastic electrical tie wraps.

Tie wrap the advance mecanism so it is fully advanced and locked.
Make sure the buckles of the tie wraps face down so the rotor
will fit back on.
reinstall the rotor and cap.
Now the distributor advance curve is "locked out."

get a advance timing light. temperairly disconect the vacuum advance vac line. start the car You'll probabily need to retard the distributor now to get it to fire, cause it will be very advanced.
Now, reset the timing at 32 degrees at idle, with the timing light.

rev the engine, it should stay at about 32degrees.
Now reinstall the vacuum advance vac hose as before.
you probabily will have to readjust the idle speed now.
It will idle nicer at a lower speed now with the extra advance at idle as compared to before. readjust the idle misture screws for best idle too.
A big cam needs this extra advance at idle and low speed.
Fill up with some 92+ octane gas and try it.
If it likes it try 2 more deg of advance to 34.

The starter may turn over slow when hot now, with the extra advance. Just open the throttle while cranking it over when hot.

The best spot for best power will be 32 to 36 deg advance.
As long as it doesn't ping. If it is about the same at 32 as 36 use 32 degrees. Less is better than too much.
Your carb is not too big but may respond to leaning down the primary side jetting for better mileage.

 

If you lock out your distributor you'll have to run
an ignition kill switch so you can spin the motor over during warm starts without distroying your starter & flexplate.
Starters don't live long when starting at full advance. The ignition kill will save it.
Once the engine is spinning with no ignition, then you flip it on and the engine will fire quickly.

 

If the kill switch is nessessary heres a simple method.
A momentary contact push button switch would be best.

 

here's a better way

 

 

they dont live as long. it over works the starter.