don't plan on beating on it (Have a 71 Demon for that) but you all know what happens when you have that 3rd pedal
The stock 318 cannot hurt one thru three, unless the box is already compromised.
In addition to banging that box with my 367; I also ran that same box for about three winters behind my 8/1Scr, 318 that had nothing but a TQ and the TTIs from the 367 and some decent valve-springs that allowed at least 5500rpm. And I banged it all winter, the first one with a CenterForce clutch with a CF-II disc. And at least one winter with the GVod behind it, what a hoot that was; Seven usable gears by Gear-Splitting.
I am not known for being kind to my junk. If it breaks, I have other and spare junk, or I just fix it.
But, you HAVE to be kind to that overdrive gear. Yes I broke one, even with the freshened smog-era-teener.
For performance;
This box works best with about 4.10s to get Second gear where you need it. But it does pretty good with 3.91s.
For fuel economy;
My smog-318 liked even 2.76s for a Final Drive of 2.01 and 65=1630 rpm... but, at this rpm it is IMPOSSIBLE to give the 318 the cruise timing that it needs, and to still be able to drive it the rest of the time.
Here's what I mean; Make sure your vacuum advance is working, then; rev your 318 up to 1630 and keep it there while you start advancing the timing. As the rpm goes up, just bring it back. Repeat more advancing until the rpm no longer increases. At this point you have reached the sweetspot of no-load timing. Now put a light on it and see where she's at with respect to timing at 1630 rpm. You cannot hurt the engine with this procedure, so just do it.
Now, don't be surprised to see a timing number of in the 40s to possibly even into the 50s.
Lets say yours dials in at 45*. That's what it wants for optimum fuel economy, cruising at 1630 rpm. How are you gonna get it?
Typically, if you do what most guys tell you to do, which I don't necessarily agree with, your base timing will be about 16*. Your mechanical advance of a smog-era 318 distributor is pretty slow and never reaches what it should so lets say by 1630 it has dialed in 6 degrees, so that totals 22*. The Vcan if also a smog era, might bring in 9*, for a grand total of 31*. So she is short at least 14*. How are you gonna get it? There are ways, but none of them are optimal until you get a standalone timing computer. And you still have to program them.
So the point I'm trying to make is that; the lowest cruise-rpm is not always gonna get you max fuel-economy.
In my experience, a cruise-rpm of 2000 to 2200 is about as low as you can go and still be able to modify the factory distributor, to the timing that the 318 wants, which could be as high as 56*.
To cruise at 65=2200, with 27" tires will take a road gear of
2.72. With a .73od in the A833 this translates to a rear gear of 3.73s..
Your
starter gear then becomes 3.73x3.09=11.53 oh yeah the 318 is gonna love that.
Your Second gear becomes 373x1.67=
6.23, still in the 6s so meh, ok for your stated useage.
Your Third gear becomes 3.73x1.00=
3.73, so I mean by the number it looks good. But if you try to pass a slow-poke on the hiway doing 55, your rpm is just 2550 so that is not gonna work. Downshifting into 6.23 Second will get you 4270, but your engine is already running outta steam.
So in other words, yur missing a gear.
With this box, you will forever be missing a gear because to get that overdrive, they spread the others out. You can move individual gears around by fine-tuning the rear gear, but that just puts the hole some other place.
However, for your stated use, this is not a big deal. I just wanted to respond to the " third-pedal" comment you made, lol. With 3.73s, it will mostly be fun just in First and possibly Second.
Yes you can, run a deeper rear gear, but
3.73s are already giving you a tire-burning low gear of 11.53, that will require a shift into Second pretty early. Second gear is the gear you will be in most of the time because ; 1) the low road-gear of 11.53 is pretty low, and 2) the third road-gear of 3.73 is gonna be, in the city, a cruise-only type-gear, because with it, 50mph is just 2300rpm. In fact, that 3.73 roadgear, will get you to 65=3020rpm, then overdrive drops it to 2200. I wouldda run this combo .......... but I had these 4.30s just laying around, and 65 was 2470 in od, so I said what the heck..... lol
