I have a 87 bronco 302 carb (2 barrel) 3.55 gears and 275/60 R15 tires that are 28' tall X10.5' wide. my millage is not good at all (avg 9.7 MPG), and i was thinking if a put bigger tires (31-33 inch tall), it may do better MPG's (at least on highway driving), or just keep my 28's?
Please help

 

Berso,
Although the bigger meats will reduce the RPMs you are turning,they are also heavier and take more HP to turn the larger diameter.Which means you probably wont see better fuel economy just through increased tire size.Regearing your axle(s) on the other can signifigantly alter your fuel economy and/or performance.
Jeff

 

i understand the concept that the gear sizes can greatly affect fuel economy and performance. what i don't understand is what gear size is ideal for a particular condition. if anyone can answer the following questions, that would be awesome. ever since i got my truck, i've been like a sponge, trying to absorb all the knowledge i can about it.

what gear ratio would be best for fuel economy?

what gear size would be best for towing?

what about 4wheeling?

what about speed?

what would be an ideal gear ratio for a 302 4x4 w/ 33" tires, for the most power, yet low rpm's (2000) at highway speeds?

why?

thanks alot!

 

Berso,

Larger diameter tires will help to lower your rpms for highway driving (make sure you adjust your gear that runs the speedometer). You may want to look into getting a K&N filter setup with the base plate that redirects the intake air. There could be some probs with your computer or inputs such as the oxygen sensor that may cause the 302 to run too rich. Make sure you have a good tuneup and set your timing between 10-15 BTDC; if it pings you'll need to back off and set the timing to 6-10 BTDC. You could also lean out the jets on your carb a little and see how that runs. You'll get a little boost in power and mileage if you install an MSD ignition, it gives a hotter multiple spark that burns more efficiently. Make sure your engine is breathing OK, no stuck heat riser valve, no restrictions in exhaust like worn out cat or muffler. Check for vacuum leaks on hoses and around intake, check EGR for proper function.

I would think you should be in the 11-12 mpg range without too much trouble.

Slik

>I have a 87 bronco 302 carb
>(2 barrel) 3.55 gears and 275/60
>R15 tires that are 28' tall
>X10.5' wide. my millage is not
>good at all (avg 9.7 MPG),
>and i was thinking if a
>put bigger tires (31-33 inch tall),
>it may do better MPG's (at
>least on highway driving), or just
>keep my 28's? Please help

 

I don't have computer at all cause is a carb. engine, in the exaust i runing headers (shorties) from a mustang, 3 inch tube, to a flowmaster,no cat, and then 2 1/2 inch tube to the rear, i don't find any leaks at all, how can i check if the EGR is good? or if is not how abount remove it, i don't have to care about smok check. I already play whit the carb, and i think is runing with the minimum amounth of gas to don't shut off. i have new sparks (rapidfire) new coil, new solenoid, new plug wires, new battery, so i don't think is somethig electric, but i'm considering to buy an MSD ingnition. There are any bearings the i must chek?
Thank's for the help.