440 questions

[Hairlesswookie]

I'm running a 75 charger as a daily driver it has a stock rebuild 77 low compression 440 and 4:10 gears performer rpm intake ignitor iii ignition summit racing 750 carb it rarely sees over 3000rpm it runs good but sense it is a daily driver i would like to maximize of mpg . I know 440 and mpg don't go together but I am getting 8.5 to 9 right now if i could get it up to maybe 11 or 12 i would be happy don't have time to pull the pistons and replace those at the moment so i am stuck with bolt on items for the moment . Would the edelbrock e-street 75cc heads work well on this low comp engine i have read conflicting things on using aluminum heads on engines with low compression this engine was measured at 7.8:1 if i remember correctly when it was rebuilt it is running 452 heads now . And what camshaft would be best for this engine I was looking at http://www.summitracing.com/parts/hrs-720021-11 or http://www.summitracing.com/parts/sum-6400 but i am eager for other suggestions . Running stock exhaust manifolds now but headers are in my plans for later in the summer . Also a local guy has some 516 heads for sale but he wants 300 for them they are stock no hardened seats price seems a little high but they would bump my compression a bit .

Thanks for any suggestions

[myk]

You want to tear apart your motor to increase MPG? 

I'd leave the motor alone and be more worried about those gears.  You can 'mod the motor all you want but with 4.10 gears you'll always be turning too much to save gas.  Ultimately, it seems like a lot of work to increase gas mileage.  If the car runs well as you say it does, I say save your money and instead of buying parts to castrate your car, buy a small beater car that gets better MPG from the start...

[Dino]

I'm all for getting more mpg, many here don't care because the car sees 1000 miles in their lifetime but I tend to rack them up fast.  That said, there's no easy or cheap way to do what you want.  You'll spend enough that you may never get your money out of it.  I have 3.23 gears, headers, and a TQ and I'm happy to get 10 mpg on the freeway.  It's lower single digits in town.  My cam doesn't help though.

Get a spreadbore carb like a street demon with small primaries and like Myk said get some taller gears.  I had 2.96 before this which makes for great freeway cruising but it needed more throttle in town, burning more fuel.  Small primaries use less fuel and if you stomp it you have the big secondaries to make the car move.  You may also want to try something in the 600-650 cfm range simply because of throttle response and driveability at lower rpm.  Nothing wrong with a 750 as long as it's not an Edelbrock Performer.   

Having an efficient engine is done by tuning, NOT by bolting on performance parts.  If they don't match then you're making it worse, not better. 

You may want to consider returning it back to stock, that's going to make it much more efficient.  Small tweaks can then be done to set it up for your driving style.  There's nothing wrong with low compression.  You're not racing it so enjoy the lower octance fuel prices.   

[polywideblock]

swap the 4:10 gear set  for a set of 3:23     will make a hell of a difference 

[ws23rt]

I'm with the others.  Your 4:10 gear will only give "good " fuel economy at a --constant--- speed in third gear that is below what we encounter in normal driving. If you want to get your mpg into the range of 11-12 mpg without changing gears . you need to hold off on the throttle at every opportunity. Ease into a move from a stop slowly and do not-- repeat ---DO NOT get on a freeway.
The truth is that your mpg is about normal for your engine and gears. I have a stock hemi with 3:54 gears that gets around 9mpg in driving with todays traffic.

[scratchinfotraction]

swap the 4:10 gear set  for a set of 3:23     will make a hell of a difference 

x2 here.

I run a stock 78 440/727/8 3/4 with a
edelbrock 750cfm/holley STREET dominator
Hughes "whiplash" cam
headers/3" pipes/muffs
stock low stall TC

  I use 3 different gear sets with the 29x15x15 M/Ts depending on what I want.

3.91sg for drag  9-10 mpg

3.23sg for HP street duty  10-11 mpg

2.76sg for highway cruzing at 55-75 mph for 12.5 - 13.5 mpg

but, the 2.76sg has been in for a while now. sweet spot is 2000 rpm at 55 mph = 13.5 mpg

a fun 440 street cruzer that is highway friendly.