Quote:
Originally Posted by matthew21lutz
It's a two drive with, as of right now  , a stock 305, th350, stock gears(I have no idea what gears) and 32" tires.
I don't want a 700r4, the 5 and sixth gears is what I really want to be able to get the best millage as possible. As far as changing everything to go with it, that's why I'm asking, I need to know everything I'm going to need to make it absolutely perfect.
I've already got new intake and carb(Edelbrock Performer & 600cfm Carb) as the stock carb just flat out didn't work anymore and the intake was cracked. Was already thinking of either rebuilding the motor or getting a crate engine.
What would be the best to get it done right, as far as heads, cam, intake, carb, gears and od tire size? Again, I'm willing to spend the money and put the work in to get it done right, my step father will be helping me out, he's been a mechanic for 30 years now but, has never done a swap like this before.
It will be a daily driver but, this will be a work truck as well. I live on a ranch and pull 2500lbs to 8000lbs pretty regularly as well, so it needs to be strong. |
You seem to be fixated that the 6th gear will yield better mpgs. It possibly will, but how much actual improvement will you see and if you see it @ what cost? You really need to consider your return on investment.
I did a quick Google search for rpm calculators. A typical T-56 has a .50 6th gear. That ratio would yield about 1350rpm @ 70mph w/3.73's & your 32" tires. A carbed sbc/bbc is going to want 2000-2200rpm to be happy chugging down the road efficiently @ 70mph. Going up to 4.56's still has you under 1700rpm. There are optional aftermarket t-56's that offer different gear ratios (like a .67 6th gear) but the cost increases w/them.
Lower rpm does not mean automatic better mpg's. It will be quieter & there will be less wear on the motor but it's not a definite that mpg's will improve. They could actually get worse because the motor is lugging to push a brick down the roadway @ 70mph.
Yes, 6pds work great for late model fuel injected cars w/ much less frontal area & weight. But it's not likely that you'll get 2-3mpgs improvement over any other 5spd OD.
The motor needs to be efficient while being able to offer good torque production @ 2000-2200rpm. A 350 w/some GM Vortec (or similar) heads, a decent comp ratio, hyd roller cam spec'd to offer optimum torque @ the calculated rpm, dual plane intake, tuned carb, good ignition, a good 2.25-2.5" exhaust, & synthetic fluids front to rear will all help you.
You want the best mpg's? Here are good questions for you:
What kind of truck (year, type, etc...)?
What mpgs would you like to get w/the "ultimate' combo in your truck?
What is your current mpg average ("it sux" doesn't tell us much)?