273 or 318

The a100 pickup I bought had engine problems ( knew this when I bought it. thats OK ) possible head gasket 273.  I'll be pulling it this weekend. I'm one of those people that prepare for all different out comes.
 I've got a question for you veterans of a100s . Of the two V8s (273/318) which should be the better choice for MPG ?
 273 small cubes/less lowend/ pulling a truck that has the aerodynamics of a brick. Or the 318 more cubes/ more lowend / pulling a brick down the road.
My thoughts on this is, you have to work the 273 harder (less torque). But since the 273 is smaller C.I. (less demaned for fuel) But what do I know ?
 I have a 727 with a 3.23 ratio/ dual exhaust
Just looking for what you guys think, if there would be much if any difference in MPG. Don't really care about the power difference so much.  But then again I have not even driven this thing yet.
If when I pull the 273 down and find problems (bad worn cylinder walls/needs pistons:affraid: )  I'll be installing a 318.

Personally, if you don't want a hotrod and the 273 is good, stick with it. neither will get good mileage though.

FYI, my 64 with a 170 /6 is getting about 22mpg... I don't think you can get there with a V8 though.

here is something to read...http://www.squidoo.com/Mopar273

If I were in the situation where I had to replace a 273 and had no engines in the garage, I'd look hard at getting a 5.2 magnum (318) and a carb intake.
You can probably find a good used one for under 1K complete. Add the intake (different angle bolts so drill or buy), carb, EI dist, and swap out the thermostat to a cooler one. Research the front drive stuff, it will be the one catch, since 70-up water pumps are different side.

You will end up with a cleaner, better running engine than either a 273 or old style 318.
Better combustion chamber, better ports, roller cam so no worries about zinc, and if you play your cards right and are able to use the new front end stuff, a single auto-tensioned serp belt. Also grab the newer starter.

The 273 suffers from lack of good piston selection, small ports (okay at lower RPM), shrouded valves since the bore is small, and no unleaded seats in the heads. Also flat lifter cam, very limited intake choices that match the head ports, and 40 year old core parts.

If you only drive your van
1. unloaded
2. around town like a grandpa
3. never on steep hills or on the highway

you might be able to build a hyper-mileage van.
Otherwise, just trade it in on the lightest, smallest 15 year old import you can find and it will beat any MPG you can squeak out of the van.
That may sound cranky and I really don't want to come down on you after our first few discussions, but most people know or can find out what it takes to get good MPG. Light, small car, tiny high tech engine, narrow high pressure tires, and drive it like you've got 40 miles to the next station and you just noticed it's on "E"!

Our vans are over 2800 pounds (most over 3K), the opposite of small, the engines are big and old tech, most of us stuff big tires underneath, and drive them all over and in modern traffic.
It's like loosing weight. Everyone knows - Diet+ Exercise. But there is always someone trying to do it without one or both of those.

All of what you said maybe and is true. But old dodge darts/ dusters/ with V8 weighted in about 2800-3000 lbs with SB mopar engines, automatics, 3.23s and guys put on larger tires and could still get fair MPG, for there old school technology. I do realize that the biggest factory would be wind resistance. As for the 273/318 it might be a draw.

Rule of thumb then;
under 3K, six cylinder, baby it, tall gears (2.9-3.2) = low to mid 20s.
under 3K, V8, baby it, tall gears = high teens, low 20s.
Add weight = drop ~1 MPG per 200 pounds (4000 car is 5 MPG less)
Steeper gears = drop of ~5 MPG per .5 gear (3.23=18, 3.73=13, 4.10=10)
Tires are too variable, I do know that EVERY tire now is better for grip, wear and MPG than those old cheap bias ply tires these vans had new. Of course, I'm running a 10" wide tire behind my /6. That's gotta take it's toll, even in just wind resistance!
Add a van body = how much less?

Wind is obviously a factor, but much more above 45MPH. It grows by multiples, not additions. They found that wings on race cars don't do much under 60 MPH.

On a big box (our vans), the big drag is not the front, but the large low pressure area created behind the van, pulling it back. Check out the research on semis and how they are getting big MPG changes with them. I'd bet you could add skirts (at the rocker panel, extending down) to the sides and figure out a drop wing for the back (like they had on old wagons) to help gain some MPG. There was an article back in the late 70s where Hot Rod did a bunch of testing on aero tricks for MPG, including vans! I remember one biggie was smaller, flared mirrors.

Here's one of many articles on the semis
http://fleetowner.com/equipment/news/trailer-aevo-device-0916

The concept is interesting, and you can do a lot, but the biggies are driving style and maintaining the vehicle. Perfect alignment, pumping up the tires to max sidewall pressure and checking them often, and running a little lean.

I bet a Neon SRT turbo 4 and a Dakota five speed combo would beat the old small blocks. Problem is, your return in gas savings would never pay off the build costs.

I've also considered a belly pan, more for aesthetics than cutting resistance. The issue there is added weight and possible cooling issues due to changing how the doghouse air exhausts. I know that this is like the wing, much more important at higher speeds. Note that exotic cars all have them, often including ground effects.

All together, you might be able to get your van up in the 20s on a regular basis, but you gotta be a MPG zealot. I think you would end up hanging with other zealots and they would think you are not one of them for even bothering with 20 MPG. I had a CRX I beat on (75MPH was slow to normal!) as a daily driver and got high 30s.
On the other hand, a 5% increase on a vehicle that gets teens is a much greater positive change than a 10% increase at 30 MPG.

Just doing a search for "Skirts for MPG netted these 2 forums.
http://www.gassavers.org//index.php
http://ecomodder.com/forum/

I'm sure there are more. Check them out, I bet they will have plenty of input.
If you get some good advise or even better, some experience with tips that work, please share them!

I know it's never going to get big MPG numbers. But what ever I can do to improve it within reason WHY NOT ?. I got over driving hard years ago. And the quest for big power has long since gone away. If I can see something in the 18-20 range HWY. I would see that as a victory. Might look for a 5.2 magnum or 318 roller pre magnum. If the 273 is not worth putting money in ( pistons exceed the worth of the 273.) Thanks

I stuck with my original 273 and loved every minute of it.

If my 273 is in decent shape, I'll be able to save buying an engine. I knew ahead of time when I bought the pickup it had some engine issues (maybe a head gasket) So a tear down was part of my budget. It shows 51,000 miles I'm sure its got MORE THAN THAT. The block is a 1964-1966 273. The heads were changed at some point with 68-69 open chamber and it has hydraulic cam and rockers. And the more universal intake setup. It does run and drive and sounds good. My biggest concern is that there MIGHT be a ridge at the top of the cylinder walls needing bored out. At that point, the 273 is not worth spending that kind of money on! But sure hope the cylinders look good. I will know on Monday.

67Dodger wrote:I stuck with my original 273 and loved every minute of it.

By the way, I'm going to try and put everything out as a unit.

The biggest trouble I had when I went through my 273 was finding original, adjustable rockers. What a giant pain. I had to search for what seemed forever. Finally found some new. Can't remember where. My rebuild came out very well in the end.

67Dodger wrote:The biggest trouble I had when I went through my 273 was finding original, adjustable rockers. What a giant pain. I had to search for what seemed forever. Finally found some new. Can't remember where. My rebuild came out very well in the end.

About 7 years ago I was at a swap meet/drag race. Wet and rain. Some guy had things for sale on a tarp  Sign said Every thing stupid CHEAP.  a lot of the stuff had gotten wet. He had a used mopar performance SB cam/ with lifters, roller timing chain set and a complete set of adjustable 273 type rocker arms on the shafts with the bolts and spacers. I looked at them. And thought I would not mind grabbing those, but did not have much extra money. So I started to walk away......then I hear  "Take all those parts with you...is $20.00 to much ?"  How could I say NO ?    there sitting in the garage right now.  true story.

just keep watching for parts

egge machine should be able to come up with the rocker arms.
i had access to a machine shop when i was doing my engine and if i had a choice between a 273,318, or 360 it would be the 273 without hesitation. as it is where i am there are none of them around and if you were closer i would buy the core from you to have. drag racers still like the 273 engine espically the older stock eliminator guys so it is worth a price...