Best mpg with a 260 and t200 combo

[DRIVEN]

Vacuum gauge goes to manifold source not ported (distributor). Your 275 tires are pretty wide too. Skinny tires have less rolling resistance. That's why high MPG cars like Corolla, Civic, Metro, Focus, etc have such narrow tires. Another small thing you can do is replace all the fluids with synthetics. I don't know that an electric fan will give you much of a noticeable gain as long as the fan clutch is working correctly. An electric fan puts a load on the alternator so it's probably even. I'd save the money. You may actually get more by converting from PS to manual. You could try an underdrive crank pulley and remove the AC and A.I.R. belts too.

 

[pontiacgp]

the advantage of an electric fan is that they are not on all the time and on the highway it should not be on at all if you are just cruising..but like Driven says they do put a strain on the alternator when on so there is a trade off

 

[DRIVEN]

Right, thanks. Sometimes I have trouble explaining my point clearly.
Electric fan: Only comes on when demanded but places slight load via alternator. Zero load while cruising. Some draw more than others. The Mark VIII, for example, draws about 50A but has close to 100A spike when starting. I would guess that it is probably around 1-1.5 hp loss to spin the alternator under full load. The stock alternator may actually not be up to the job.
Stock clutch-type fan: Only locks up when demanded by high temperature. Normally "slipping". Almost zero load while cruising. When sitting in hot traffic or pulling a long hill it will "lock up" and spin faster. The loss is probably in the same 1-2hp range.
So, given the two options, I'd probably just leave the stock clutch-type fan and save the money. Just my opinion. I remember Hot Rod or Car Craft doing a fan dyno shootout a few years ago and the stock clutch-type fan used less hp than either a fixed stock fan or several flex fans they tested.

 

[pontiacgp]

And if you stay with the stock fan make sure the clutch is working, if it's seized the spinning blades not only needlessly use power (gas) to spin they create a wall which impedes the airflow and causes resistance.

 

[DoubleV]

My thinking with the 275/60 is to further raise the gear ratio. I guess there is a point when this becomes overkill?

IMO yes. It seems like you are willing to spend more money than what it would be worth in gas savings. Good fuel economy is a great thing, but if you have to go to such extremes to eek out such a miniscule amount more, than I think it may be time for a more modern fuel friendly car IMO.

 

[Csilvy2000]

This site is awesome! I've been here two days and someone is propositioning to buy my cutlass!

Seriously, I always do the cost analysis in my decisions. I'm using the car about 400 miles a week. The car is paid for and insurance is cheap. I love the car and it is very reliable. I'm thinking a stronger coil for 35 bucks, fan and thermostatic switch for another 40 and some fabricated aluminum underlining for 40. I figure in a couple of months all the upgrades will pay for themselves.

 

[88hurstolds]

Raising the gear ratio can actually hurt your MPG since it will take more power to turn the rear wheels.

 

[Csilvy2000]

These 260's make gobs of power!

I wonder how long it would take for a set of headers and a dual exhaust set up to pay for itself?

 

[pontiacgp]

These 260's make gobs of power!

I wonder how long it would take for a set of headers and a dual exhaust set up to pay for itself?

that's usually a losing battle...headers and duels sound nice and nicer with your foot into it...

 

[thedoctorisin]

I had the same 260 200c 2.29 setup and got around 18 on the freeway.

With my lightly modded and tuned LT1 and a 700r4 2.29 locked I can get 25-26 driving mountain roads and the freeway.

The overdrive transmission will save you gas waaay before the dual exhaust will. I will say that having a louder car kills my city driving but helps on the freeway.

My speedo and odo don't work cuz my 700r4 is a vss not cable but I usually pass people on the freeway. I use gps when I'm cruising on long trips or by the CHP, average is probably 70-75 mph getting avg. 25 mpg is say is pretty damn good.