Slant 6 MPG Upgrades?

autopar3000 said
Some thoughts, as others may have mentioned and some of which you've noted:

- With the cost of aftermarket EFI and all the mods you will have to make, it will take you a loooong time to pay it back in fuel savings. If you're doing it largely for the fun of working on the car, then I can support that 100%.
- You will get better fuel economy with a later slant that has the cast crank. The cast cranks are something like 15 lbs lighter, which is a huge difference in rotating mass.
- Highly recommended you figure out that electric fan situation. On my old warmed up 318 getting rid of the fixed fan was worth around 1.5 mpg on the highway (at 70+ MPH). I had a 3.23 gear with a 26" tire, so about the same RPMs you're looking at.
- Look for a 2.76 rear gear. Will be the biggest bang for the buck fuel savings, and with a 7¼ rear you should be able to get the gears super cheap (or even free) from someone here.
- Don't discount the value of synthetic oil and differential fluid. Trans fluid probably helps too, but I'm not sure if it's a lot.

- I'm not so concerned about how long it takes me to make back what I spent. I like working on my car, and want it to run the best it can. I'll make back the money in a few years at least, but I'll have had fun making the change and figuring it out.
- I didn't know that about the cast cranks. I was under the impression they were garbage but yeah that's a good amount of weight reduction.
- If I were using a stock radiator or even one close to stock it wouldn't be an issue fitting on the electric fan. I went with an aluminum rad, and it's significantly thicker, meaning there's barely any room between the front of the engine and the back of the rad. There's enough room to fit a direct fan, but the electrics I can find are too thick in just the wrong places, or just totally unreliable if they do fit. It's the top of my list.
- Yeah before I dump $3k into an overdrive, I'll look at swapping to 2.76, it may be exactly what I'm looking for. If not, I can always go back and spend that money later.