318 engine, MPG and what makes it better

[YY1]

does kind of sound like a diesel...

back off the timing just a touch

 

[moper]

Do the upgrades to this 318 (performer intake, 600c/ 4 Bbl carb, headers & glaspacks, 727 trans, unknown cam)
change any specs or numbers as far as timing and tuning?

Just the fuel changes over 40+ years change the tune up requirements. Adding non-stock parts will certainly demand a completely different tune up than the factory 2bbl on leaded fuel. Never mind that same stock 2bbl on unleaded crap...
That's why I suggest research. Not asking the web - go read articles over and over until you get it. Then you can apply what the various opinions will give you.

 

[Speedbird]

I can only tell you about my experience with 318 daily driving.
I think he is running a square bore carb.
I run a Q Jet, 215/70/R15s, lock up transmission, stock ignition, 2.76 rear IIRC.
I get around 23 MPG highway.
But it's a Duster.

 

[levicah]

I can only tell you about my experience with 318 daily driving.
I think he is running a square bore carb.
I run a Q Jet, 215/70/R15s, lock up transmission, stock ignition, 2.76 rear IIRC.
I get around 23 MPG highway.
But it's a Duster.

It's a edelbrock 600 cfm 1406 4Bbl. What is a "square bore carb"?
And yeah, anything north of 11 mpg would be a start!

 

[YY1]

square is all four the same or nearly the same size

spread is front primaries much smaller than secondaries

 

[rumblefish360]

It's a edelbrock 600 cfm 1406 4Bbl. What is a "square bore carb"?
And yeah, anything north of 11 mpg would be a start!

An example of a spreadbore carb is a ThermoQuad (TQ) Quadrajet (QJ) or a specific Holley. (Hard to find)

An example of a squarebore carb are most every other carb. Edelbrock/Carter AFB/AVS, most every Holley like the 4160/4150 or Dominator carbs. Some of these can have slightly smaller primary venturi’s. This does not disqualify them from being a squarebore.

Squarebore carbs are well liked because they are more uniform in the amount of air and fuel they deliver.

Spreadbore carbs are well liked & favored for dual purpose cars that seek high throttle response & mileage with the small primaries and often explosive secondary power with what is normally massive secondary butterflies.

The TQ has 2 sizes on the primary side. 1.38 for engines, excellent on 340 and smaller engines & the 1.50 which came on larger engine. (The larger primary was very helpful in throttle response and drive ability on the larger engines)

The secondary side on any TQ is (IIRC!) 2.25 per butterfly.
(I may have to go home and re measure! Could be 2-1/2. I’m doubting myself right now. But I think I’m right. I’ll check later to be sure.)
Spreadbore carbs have a little bit of a problem with good fuel distribution as well as the intakes that they come on and aftermarket one designed for them. While that can be fixed, it is a step most do not take.

But they are really quite excellent when used right.
Parts for them are they other draw back. Not exactly on the corner stores shelf like a Holley!