Need to make a decision fast 5.7/6.1/340
Cannot and do not agree with this - as Ive run both types of motor thru a 3400 PTC stall , 727 full race trans and 8&3/4 diff.
14mpg vs 21mpg highway over two hundred miles st 70deg - 80 deg F
If I was asked what made the difference, Id say infinitely superior combustion in a better designed alloy head, better breathing through much better designed ports, MAP advance ( my old LA ran a mech advance dist only) , and superior ignition characteristics plus a smaller hyd roller camshaft making more power than a larger flat tappet.
Id be appalled if a modern motor only showed the MPG return of a 50 year old design - race spec or otherwise.
I used a carb set up on my hemi. It had the older XFI273 cam, and a 2400 stall converter. I got 17 MPG city to 25 Highway, I put 60,000 miles on my 69 Barracuda before it got T boned. Since I was using a 727 trans, and 3.23 gears, as you can imagine, that equates to 3 grand, or more just to drive on the interstate, and keep up with traffic. I hate driving alone, if there's a car a mile ahead on me, I need to rush up and be 150' behind him. So I drive 70-75 MPH. Most of my driving was from the coal region of PA, to the Jersey shore where my Mom lives. I did install a 180 degree thermostat, although I resigned myself to the fact that, no matter what I did the car would run at 210 spot on all the time. I think I tuned it once with a vacuum gauge, and changed the plugs once. It was rock solid reliable. As far as somebody else put it " You need a BFH to install it," That's true, and it's not. In a 1968 Barracuda with 340 Torsion Bars, It was a matter of lifting it over the Radiator support, and dropping it in. No harder than a 440. I did have to manipulate the engine engine a bit toward the passengers side, and I had to push on the trans tail shaft with my feet, while trying to bolt it up. ( that worried me, but it never amounted to anything.) I converted it from 340, to hemi in 3 days, and it was on the street. The hardest part was tapping into the start, and run wires, and figuring out where I wanted to install the electric fuel pump.
On the reverse side of the coin, I work all winter through the snow to change the suspension, and build my 75 Duster, and I'm still having headaches. One inch Torsion bars do not clear my TTI headers without major squashing. ( Although if you call TTI, I got the very first set of headers, and A body mounts. 2007 XV motorsports.) So, TTI say they may have changed them since. My Carb set up will not fit under my hood without a scoop. I can't use the angled oil filter adapter, the passenger motor mount is flush with the oil filter mount. I've heard some people say, they had trouble installing the starter. I just had to shave an ear off the block. I can change my starter from above the engine, if I put a bit of force on my brake lines. I did have to move the proportioning valve back an inch to clear the headers. In my 69, I had to drill one hole in the passenger side firewall to bolt the transmission in, on the 75 I didn't. All in all, each A Body is a variation of the same specs, but not very consistent. Still knowing what I learned on the first install, it took 3 hours rather than 1 to pop the engine in, and slide it aside. The rest of the car is a F**kin' nightmare although.
