I don't think your setup is far enough gone to really cost you mileage.

I haven't worked the numbers yet, but a 33 inch tire with 4.10s probably works out about the same as my stock size with 3:1.

 

Found an online calculator. With 33 inch tires and 4:10 vs my 27.7 inch and 3:1, at 1500 RPM in drive I should be running about 42mph. Yours should be running about 36.

Given the slack in my converter (not sure if it is stock or not, but it's nothing serious), we're likely a lot closer than that.

 

Any updates?

 

Sorry for the silence in posting anything - work and family has been the priority lately. For the time I had to work with, installing the electric fan and 3G alternator was the focus. Here are a few pics:





One slight carb change was going back to the orange cam. While the pink cam worked fine during the summer heat, it did not introduce enough fuel now that the weather has turned cold. In spite of experimenting with the choke, accelerating from a stop resulted in a bad stumble until the engine got pretty warm. Ultimately the orange cam avoided this situation.

Another learning that came with the cold weather was more careful use of the choke based on observing the AFR gauge. While all my tuning work has driven me to lean mixtures for maximizing MPG, this presents a challenge when the engine is cold (40 degrees) and fuel is less effectively atomized. One idea I've been contemplating is to separate the choke functions into two separate controls. In the summer, I didn't need to richen the mixture when first starting the engine, but needed a bit of constant throttle (+200 RPM or so) until the engine warmed. However, now I need both and sometimes would like to just operate the butterfly in the air horn. I recognize this isn't so practical and the truck runs just fine, but I'm driven to tinker and try to optimize.

 

I wondered how winter would affect it.

I haven't done much to mine either, MSD is still waiting to be installed.

I'm seeing the benefits of EFI right about now. The project would be over and I'd just be driving. It isn't for lack of wanting to tinker, just lack of time.

 

I finally verified my old carb was leaking internally. Always nice.

Swapped it for the other 600 and added a 2 inch phenolic spacer, can't quite get the idle where I'm happy with it, but it runs much better and even with a *lot* of testing and tuning it still averaged 7mpg, which was about what I got driving like a grandma with the old carb last time.

Hoping to get the MSD installed later today.

 

Are you running manifold or ported vacuum?

 

I'm running manifold vacuum. Sounds like you're making some progress. I've been distracted by replacing the timing chain which has taken me longer than I'd hoped. The clunking noise finally got to me and I found over 1/2" of slack in the chain. I'm curious to see if this makes my idle a bit smoother.

 

That should retard the cam timing. I wonder what the best cam timing would be for efficiency. I think retarding it would probably be best, but often more power=better efficiency.

 

Just quick results, installed my MSD, still a lot of testing and tuning, wasting fuel, playing with the carb, pushing the timing, lots of idling in my driveway, still went from 7.04mpg to 9.68mpg.

I think my timing was too high (20* initial!) and the spacer was causing it to lean out a bit. I may be closer to your experiment than I realized, going about it a different way to get the same results.

 

That's a great improvement! Yea, seems like 20 degrees initial is on the high side.

 

My highway mileage dropped from 12.5 to 10.1. Pretty sure it is because it has a 160 thermostat, first long drive in the cold. Just swapped it for a 195.

What are you running in yours?

 

I've got a 195 degree thermostat. Out of curiosity, how are you calculating MPG?

 

Old fashion way, fill it up, do the math.

12.5mpg was nearly 100% open road driving.

The temp guage was just above the bottom with the old thermostat. It sits above the M now.

I've got a set of real guages, just haven't put them in yet.

 

New stat, mixed driving, 10.43mpg.

You've still got me by a good margin.

I'm probably going to change the mains from 64 to 62 since I already have them. Still not quite behaving itself at low rpm, that is probably hurting my mileage.