The Stovebolt Site Forums The Shop Area Engine Shop Running Temp?

I have some gas mileage issues in my '58 1/2 ton with a rebuilt 283 that starts, runs and sounds super but sucks the fuel(I am even driving conservatively). Now that I have a working temp gauge I know it runs at a steady 160 degrees. Doesn't vary even on a hot day. My question is should I put in a 180 degree or higher thermostat? will a hotter engine burn gas more efficiently? I just gased up and will check the mileage at 160 degrees.

What rear end ratio and what size tires are you running on your truck ? Those numbers have much more to do with gas mileage than thermostat temperature.

I've got a 283 in my 66.It's really good on gas
What carb manifold and cam are you using?

The two barrel is started with was a joke!
We went to a four jet and stock manifold...got better

Big ramshorns duals and a two-plane w/holley it got good

Tall tires,taller diff ratio...now it's KILLER!!!

Doesn't stop but runs fine!!

I know there's a lot that goes into gas mileage. Where do I start? I have a reasonalble? rear end at 3.7 and my tires are radials p235/R75/15 on original 15 inch rims. I'm about 3000 rpms on the freeway but keep up just fine, doesn't seem too stressed. I still have the original 3-speed transmission (on the tree). I was hoping to do better with a new edlebrock carb(600cfm- settings out of the box)and matching intake manifold. I have set the timing of the new HEI distributor with vacuum gauge and light. currently about 8 degree BTC since it doesn't start well at 4 degrees. I think I was stupid and let someone talk me into a different cam that was supposed to be better at low end range and be OK with gas mileage. I think that is why I can't get my vacuum above about 12 inches at idle? Is that my problem? I saw the recent posting about setting timing at a faster rpm with a vacuum gauge and thought I should try that. I like driving the old truck but what kind of gas mileage should I be getting?

I've got the Edelbrock Performer 600cfm carb on my truck, with an edelbrock Performer intake manifold, mild hydraulic cam on a 350 ... 350 TH ... 12 bolt mid-70s rear end ... I'm turning 2000 rpm at 70mph on the highway ... and getting 14 - 16 mpg.

Did you tune up the gas'air mixture on your carb? 2 screws -- turn 'em clockwise until the engine starts to run rough, counter clockwise until it smoothes out, and then 1/4 turn more counterclockwise, and you're set.

I wish I was getting 15 mpg! I adusted my carb screws just about like that- maxed out the vacuum and counterclockwised a 1/4 turn. I'm obviously running a higher RPM on the freeway. I guess I may be left with changing the rear end ratio, getting bigger wheels or getting a new transmission although I like my old 3 on the tree!

find a 3.38 ring n pinion to drop the RPM [should be avail at specialty rear gear places, but also @ Patricks], and yes - get the temp up - always use a 180 stat for a 283 - they like hot and slow - they'll take higher revs, but they were made for max torque at about 2000RPM and will get better mileage there - sounds like yer doin it right otherwise!!

Bill

If you are only getting 12 inches vacuum at idle at sea level, then you need something more than a low rear to get your milage back up, you have a performance cam. You will need to figure out if you have it dialed in correctly, maybe retarding or advancing the cam timing a bit would fix it up, or playing with the advance curve on the distributor, or both.

I would like to thank everyone for their advice. The rear end project seems like a good one for me to do. I agree there seems to be a problem with my cam/vacuum. Does cam timing involve taking off the timing chain? advance or retard the cam relative to the crank and see if things improve? I'll look in my shop manual. I have ranged my distributor back and forth to change the timing but can't get the vacuum up that way. Thanks again, Bob