Gas price exploded in canada since october , we pay 1.68 $ @ litre of gas ...i dont mind the duster and its gas consumption for fun summer days once in a while...but my new toy , 69 ratty valiant makes my mind go in all directions , goals are weird...* Have a ratty looking car with patina and old funny notlagia look ( 1970s -hippie style ) little lumpy cam , black steel wheels , light body and components but...i wanted a sleeper an ugly rocket ahahahah but with the prices so high im telling myself that maybe my stockish 360 with 350hp ( xe268 cam ) with a 904 reverse valve body ( 2 200 stall ) and highway gears could be the way . Theres the a833od that is still available too, but the car was born : 273 2bbl and 904 , i wanted to keep the look too , all kinds of ideas passed by with a 3.9 magnun v6 swap even a srt4 4cyl swap..but even then doing all the work and $$$ modification will be tricky , i tought about buying a cheap 318 and sleeve it for 273 pistons but even there it will be $$$$. So 360 / 904 /2.xx gears and 20 mpg ? With a 2 500 pound valiant ? Your toughts !
I bumbled thru the first page of responses, but not really wanting to sift thru all the off-the-wall stuff, to see if anybody got to the meat and potatoes........ so:
There is a simple solution to your dilemma, namely; overdrive.
I like what
@66fs said , and anyone else that is on track with him.
Every time I offer opinion, people jump on me, so I'm not gonna do that this time. Instead I'll tell you what I actually already did.
Like my Avatar shows; final iteration is 367/A833/3.55s
I chose each of these components with fuel efficiency as the primary consideration, and modest power as a secondary.
I had at least One example of every LA SBM, in my shed.
I had at least One example of every transmission that would bolt up to any LA, both automatic and manuals.
I had at least One example of every A-body rear-end, except a Dana, and
I had at least One example of nearly every rear gear from 2.45 to 5.13 skipping; 3.73s and 4.56s
These were my options.
I chose the manual trans for efficient power transfer, to gain mpgs, so I could run a bit more cam.
I choose the 8.75 for it's easy-swap pumpkin.
I chose 3.55s for their dual-purpose versatility
Knowing this would be a modest performance combo, and
knowing that the 367 could fall together cheap at near-zero deck, and
being desirous of the 1.7 r/s ratio for piston dwell time at TDC, and
knowing that a longer stroke would allow a lil more cam before loosing cylinder pressure,
I choose a 360..
To run a smaller cam, I reasoned that this engine would need some extra cylinder pressure. To get some Power back, due to the loss of valve duration, I choose a better-flowing head. To take advantage of the piston dwell, I reduced the cruise rpm drastically with overdrive. To get out of the rut of a crappy starter gear, I choose a trans with a 3.09 low in it. To get low-ET back, I installed a Gear-Splitter.
Did it work?
Hell yes!
on a certain Daytrip-test, she pulled down 32mpg USg
At the track, she went
[email protected] on 245 street tires@3650 pounds/me in it.
This is what I have already done.
this is not imagination,
not puffed up keyboard tickling;
this combo sits in my carport as we speak.
And you can come to my house with a trailer and a bag of cash and take her home. Or if you wait a few weeks, I'll change the gas and oil, and then you can fly over and drive it home.
If you want details;
some most excellent fellow FABO member bought me a Gold membership (thank you whoever you are), so I now have lots of room for Conversations. I am semi-retired so I got lots of time to talk.
Consider that your car needs a certain amount of horsepower to cruise at a certain roadspeed. Various chassies have various power requirements, but our ancient Bricks generally run between 40 and 50 hp.
This requirement can be converted to pounds of fuel per hour.
Lets say your chassis requires 40hp, that converts to about 20pounds of fuel per hour at WOT AFR, which is 20/6=3.33gallons per hour.
But you don't run at 12.5 AFR, maybe you run at 15.0 AFR and the requirement is reduced to say 2.7gallons. At 60 mph that is 60/2.7=22.2 mpg. This is what the typical A-body chassis will require.
The car does not care how it gets its cruise requirement.
You can run a big engine at a low rpm,
or you can run a smaller engine at a higher rpm,
So long as it meets the power requirement.
Or you can throw rpm out the window and convert the power requirement to cfm. Now; you can gear the rear end to vary the throttle-opening to meet the cfm requirement.
See how all that works?
No? Ok well the 318 in a late 80's tank of a NewYorker, is known to get very close to or just over the target 22.2 mpgs by gearing it down with 2.45s, a loc-up A999, and tall tires to....65=1900rpm. Therefore you know that 22.2mpg is a good target.
We know that if this New Yorker hauls a hard-shell camper, the mpg will plummet. Why? Because the hp requirement has changed.
Now, you can put a 400hp 360 in there and NEVER achieve the target. Why?
Because this type of engine, at 1900rpm is not very fuel efficient.
But you can take that 360, and pull that monster cam out of there and swap in a 318 cam, and with 200psi cylinder pressure, again creep up to the target 22.2mpgs. In fact, if you build the 360 right, you can exceed the target. Why?
Because the 318 at a modest 130psi cylinder pressure, was not very fuel-efficient to start with.
Edit; And it burns 87E10 full-time, with full-timing.