1997 chevy s10...next mod

[kir_kenix]

Hi guys, long time lurker here.
Well, I have this 1997 chevy s10 2.2 liter that I use for work/school. I drive probably 60/40 city in this vehicle. While taking longer trips, I've found that 30ish mpg is deffinately doable, but my overall average is closer to 26.5. I havn't done any hard core mods, but I've done a few little things.
+Complete tune up (plugs, wires, pcv, fuel filter, k&n, etc)
+synthetic oil & differential fluid
+AC delete
+40 psi on new tires
+135 amp alt with smaller/lighter pulley

I have a smaller/lighter crank pulley on order, and I have new o2 sensors sitting in my tool box. I'm trying to decide which mod/mods should be next in line. I need to have a toolbox for work, so I was forced to take my toneau cover off. Thinking of these mods, but not necessarily in this order:

+Body kit
+flat hub caps
+e-fan
+computer tuner
+grill block
+shorty antannea or relocation
+LED's all the way around
+header/cam/complete rebuild (headjob, ultralight connecting rods, etc)
+gear swap (3.73 to 3.08)

I plan on buying the scangauge this week so I can verify any improvements. I guess what I was wondering is which mod, in your opinion, should I go with first. I've done quite a bit of mechanical work, but not so much in the way of aerodynamics. My goal is to be able to get 33-35 mpg out of this truck overall, while still maintaining its usefulness as a truck.

Thanks for the advice guys

[Joenavy85]

as far as a rear end swap, where does the engine rpm sit at highway speeds?

[kir_kenix]

Originally Posted by Joenavy85

as far as a rear end swap, where does the engine rpm sit at highway speeds?

Going to need scanguage to determine that...no tac. I do most of my highway/interstate driving at speeds over 70mph, so I know there is probably alot to gain there with a ring and pinion swap. However, I havn't looked into it enough to determine if I can reprogram the ECU to adjust my speedo.


Sometimes I pull a small trailer (500-700 lbs), and I often have 250-400lbs in the box for work. That is the only thing that gives me pause on gear ratio swap.

We may be moving to a more rural community, which would force me to drive this truck about 65 miles about 5 times a week. If she gets this job, I'm going to need to milk as much out of every tank as I can.

I'm thinking that e-fan or grill block will be my easiest mod that will have the biggest gain. Hoping somebody else has been thru this process and can help me prioritize.

[MarkM66]

Wouldn't you want a larger alt. pulley for economy?

It would turn the alt. less rpms.

If you don't have a temp gauge, I'd get one before you start doing grill block mods.

[Weather Spotter]

I would go for the e fan, its a gain that will be there 98% of the time. It will help reduce engine load, and will help it warm up faster.

[kir_kenix]

Originally Posted by MarkM66

Wouldn't you want a larger alt. pulley for economy?

It would turn the alt. less rpms.

If you don't have a temp gauge, I'd get one before you start doing grill block mods.

Yeah I could see that. However, with the smaller/lighter pulley it puts out 14.7 at idle and keeps the engine from "surging" (revving up to keep volts up). The larger/heavier pulley ran between 14.3 and 14.4 at idle and when I ran my stereo and lights (my toolbox and tailgate have 10 small amber bulbs that turn on when I run my lights) at idle everything got dimmer. With new alternator pulley it no longer dims and runs smoother (no more surges). I think switching from these lamps to LED 194 buld equivelents might save a bit of juice. It is about 60% of the mass of the stock pulley, so it is probably a wash.

I have a temp gauge, but good point. I'll monitor it closely.

[kir_kenix]

Installed a hinged, homemade toneau cover over the rest of my box. Made of chloroplast with an aluminum frame. Also installed a "pool noodle" slit in the middle and ziptied to my bumper to prevent so much air from entering the engine compartment. Will post some pictures when its not snowing. I think the open box was creating alot of drag, and I'm glad I was able to build something really light and really cheap to combat that.

Made some massive improvements to gas milage already. Drove 367 miles on only 10.6 gallons of gas (34.6 mpg). This is the best tank I have gotten in quite a long time. Tomorrow I'll be putting close to 300 miles on it, so I will see how the improvments continue to help me post big numbers.

If I can find some clear plastic I think I'll play with blocking off the grille next week.

[Joenavy85]

Originally Posted by kir_kenix

Sometimes I pull a small trailer (500-700 lbs), and I often have 250-400lbs in the box for work. That is the only thing that gives me pause on gear ratio swap.

First step is definitely a Scangauge (or an ultragauge). Grill block would likely be the second step. since you tow a trailer occasionally and carry stuff in the bed i would try to find a good dyno chart for your particular engine before considering a rear end swap (don't want to bog the engine down with the extra load). when monitoring temps an ultragauge is nice because you can set an alarm to sound at a certain temp, so if you normally run around 190 you can set the alarm for 200.

[kir_kenix]

Ordered a scanguage today finally! Hoping to get some rpm/load data to decide on gear swap feasability.

I also went ahead and ordered LED's all around (tail, turn, liscence plate, marker, and the 10 on my toolbox). Not sure how much of a difference it will make, but I figure that I'm running about 70watts of bulbs (not including headlights) as I cruise down the road. The new bulbs will use about 12-13% this amount. Hopefully this means I can return to a stock pulley size (I will probably find an aluminum one to save weight) and save some fuel.

Blocked off the lower grille tonight to see what the temp will run on my way to school tomorrow. Averaging just over 27 mpg on this last tank, and all of that was with 500-700 lbs in the box plus a passenger. I'm confident my mods have increased mileage some, just that I havn't had an oppertunity for the gains to show up on paper yet.

[kir_kenix]

Been doing some math on a gear ratio calculator. Looks as though switching from 3.73 to 3.42 might be the most viable swap.

My engine makes max torque at around 2800 RPM (only 130 ftlbs). I don't think going taller in the rearend will hurt me much here because I'm still putting out just shy of 110 ftlbs at 2,000 rpms. (Ignore red line)


5th gear is a generous .83 to 1 on these puppies, and 4th is 1:1.

3.73 rear end (what I currently have). If you look at speed in 5th gear:
2000 rpm pretty well represents most gravel driving I do now
2250 rpm represents most 2 lane highway driving I do now
2500 rpm is 68 mph, usually about all should I do on the interstate…she does poorly mpg wise above this


Hypothetical 3.42 rear end swap. It seems to me that I could reasonable drop about 250 rpm’s off my cruising speed. If I’m pulling my small trailer, I can just stay in 4th gear and maintain the same mileage/economy I was getting with 3.73's.



I’m having trouble seeing a reason why I shouldn’t do the swap. I know I’ll give some up on the bottom end, but I usually pull a pretty light trailer. Turbo and intercooler are sitting on a shelf in my garage if I have any trouble getting up to speed with the new gears .

Any thoughts/input?