With these trucks, gas mileage is not a strong suit, although, fuel economy can be increased for relatively cheap and especially with the price of gas, will save you a lot of money. I did some mods to my truck which helped my 350 TBI in a 1988 square body Blazer get in the 20s cruising on the parkway with 33” mud terrains and 3.73 gears. Some of these mods many people may disagree with, but this is what has worked for me and I have seen the difference, so take it all with a grain of salt. Naturally, make sure the truck is in good working order before even trying to increase mpg.
First thing I started with is ignition.
-I had some old spark plugs so I decided to swap them for some new ones. When I went to the parts store, I was going to buy some Delco plugs, but one of the fellas I know who was a mechanic for decades brought of e3 plugs. They offered increased power and fuel economy. The power I doubted but I figured more surface area for a spark to reach couldn’t hurt and it was a little cheaper than AC Delco in my case. Now, I know online e3’s get a bad rep especially in these engines and I understand why. I put these plugs in my motor and it ran like dog crap. Truck felt down on power and sluggish, but instead of changing the plugs immediately I decided to try something else.
-This brings me to ignition coil. I had a brand new generic coil in the truck and I figured it was so cheap, I might as well just get an upgraded one. My guess was the new plugs with more spots for spark to jump might have needed a bit more zap. So I got an ACCEL supercoil. Advertised faster starts, better power, and mpg. All I was concerned about is the higher voltage, I know that the coil will only put out the amount of voltage needed to jump the gap no matter what, but I figured I’ll give it a shot. Boom immediately the truck was running much much better compared to the old plugs and coil. My guess is these e3’s get a bad rep in these trucks because you just need a bit more zap. No misses or sluggishness.
-Next up I put in a brand new set of ACDelco professional spark plug wires. I made sure to keep the wires separated using an old zip tie trick, just for sake of easy diagnosing and keeping any cross arcing when they get older. New wires were just to make sure all the power made it to the plugs efficiently.
-Next up was timing. I read extensively into this and saw many guys saying against bumping base timing and that it will not do anything as the computer will readjust it down. I figured it’s a quick thing to change and I read some good so I figured hell, why not? I bumped timing to 3* advanced with wire disconnected. 4* I felt was a bit too aggressive for some 87 octane gas but if you use higher octane you can probably bump up maybe max 6*. This helped make a big difference also to wake the truck up, the timing helps fuel economy, and after reconnecting the computer advance and using a light, I can see that the timing at idle bumped up about 3 degrees from where it was with computer connected originally.
-Lastly for ignition I replaced my distributor with just a cheap stock replacement due to some pickup coil corrosion in factory, and I put a brand new ACDelco ICM in the cheapo as a safeguard.
Second topic is air.
A good running engine needs air. Cold dense air.
-I first swapped a basic fram air filter for a K&N oiled one, I know some guys love them, others say they let more dirt through, but I got the filter brand new as a nickel item at advance so it was only .05 cents instead of $100+ (part #e1500)
- I also stuck the thermac flap open, I kept the factory intake, which for the squarebody’s goes out through the radiator support, but just jammed the flap open so it is constantly wide open, as previously it did not work and stayed shut.
Third topic is fueling.
-first is more or less tune up. Make sure new pump, pump strainer, filter, and clean lines. After some extensive rust, I just replaced all my hard lines with high high quality rubber lines and a brand new filter. My pump I replaced with a Delphi stock replacement that puts out 30 psi for more gas moving to our now better breathing motor.
-I stacked two injector tower gaskets to make a homemade injector spacer, the spacer seemed to change the power band of the motor, just slightly. It is supposed to help atomization and increase airflow. Again I figured why not because for me it was free, and if you buy one it is max 15 bucks.
-To increase fuel pressure with now much more air and more aggressive timing, I just did the classic quarter mod. Costed me .25 and bumped my fuel pressure to around 14 psi. A quick note is if you have low fuel pressure and the motor sees you are running lean, it can cause the ECM to command more fuel to dump in, causing much much worse economy.
Fourth topic is the back end…. Exhaust.
The factory exhaust is extremely restrictive. I have a cat delete with an exhaust cutout. It’s loud but it noticeably increases mpg. Back pressure is not good. In another post I am doing an experiment with free flowing exhaust for economy, and how far you can get before popping an EGR code.
Fifth topic is the most important by far.
-Right foot usage. No matter how efficient you may make your motor, your acceleration will decide how you will do economy wise. Ease into the throttle and roll to stops. This will by far have the biggest impact on economy and hey, we all have old trucks, if we go slow people won’t honk, they will just angrily speed around.
Overall, besides that I just run synthetic shell Rotella 5w-40 and try to avoid stop and go, although city mileage isn’t too bad, it definitely isn’t nearly as good as parkway. Some future stuff I want to do is to take off the smog pump belt, I understand it doesn’t have much of an effect but I have no cat so no point turning anything more than I have to with the motor. Also maybe an electric fan to help reduce load, and probably a cheapo TBI spacer to help atomization of fuel, another polarized topic, but I’m curious to try it. In conclusion, many might see this thread as a sales pitch of snake oils, but it is what has noticeably worked for me and many mods have increased my power making this brick into a beast on the parkway. Do with it what you will but it is what worked for me and maybe will help someone else.
First thing I started with is ignition.
-I had some old spark plugs so I decided to swap them for some new ones. When I went to the parts store, I was going to buy some Delco plugs, but one of the fellas I know who was a mechanic for decades brought of e3 plugs. They offered increased power and fuel economy. The power I doubted but I figured more surface area for a spark to reach couldn’t hurt and it was a little cheaper than AC Delco in my case. Now, I know online e3’s get a bad rep especially in these engines and I understand why. I put these plugs in my motor and it ran like dog crap. Truck felt down on power and sluggish, but instead of changing the plugs immediately I decided to try something else.
-This brings me to ignition coil. I had a brand new generic coil in the truck and I figured it was so cheap, I might as well just get an upgraded one. My guess was the new plugs with more spots for spark to jump might have needed a bit more zap. So I got an ACCEL supercoil. Advertised faster starts, better power, and mpg. All I was concerned about is the higher voltage, I know that the coil will only put out the amount of voltage needed to jump the gap no matter what, but I figured I’ll give it a shot. Boom immediately the truck was running much much better compared to the old plugs and coil. My guess is these e3’s get a bad rep in these trucks because you just need a bit more zap. No misses or sluggishness.
-Next up I put in a brand new set of ACDelco professional spark plug wires. I made sure to keep the wires separated using an old zip tie trick, just for sake of easy diagnosing and keeping any cross arcing when they get older. New wires were just to make sure all the power made it to the plugs efficiently.
-Next up was timing. I read extensively into this and saw many guys saying against bumping base timing and that it will not do anything as the computer will readjust it down. I figured it’s a quick thing to change and I read some good so I figured hell, why not? I bumped timing to 3* advanced with wire disconnected. 4* I felt was a bit too aggressive for some 87 octane gas but if you use higher octane you can probably bump up maybe max 6*. This helped make a big difference also to wake the truck up, the timing helps fuel economy, and after reconnecting the computer advance and using a light, I can see that the timing at idle bumped up about 3 degrees from where it was with computer connected originally.
-Lastly for ignition I replaced my distributor with just a cheap stock replacement due to some pickup coil corrosion in factory, and I put a brand new ACDelco ICM in the cheapo as a safeguard.
Second topic is air.
A good running engine needs air. Cold dense air.
-I first swapped a basic fram air filter for a K&N oiled one, I know some guys love them, others say they let more dirt through, but I got the filter brand new as a nickel item at advance so it was only .05 cents instead of $100+ (part #e1500)
- I also stuck the thermac flap open, I kept the factory intake, which for the squarebody’s goes out through the radiator support, but just jammed the flap open so it is constantly wide open, as previously it did not work and stayed shut.
Third topic is fueling.
-first is more or less tune up. Make sure new pump, pump strainer, filter, and clean lines. After some extensive rust, I just replaced all my hard lines with high high quality rubber lines and a brand new filter. My pump I replaced with a Delphi stock replacement that puts out 30 psi for more gas moving to our now better breathing motor.
-I stacked two injector tower gaskets to make a homemade injector spacer, the spacer seemed to change the power band of the motor, just slightly. It is supposed to help atomization and increase airflow. Again I figured why not because for me it was free, and if you buy one it is max 15 bucks.
-To increase fuel pressure with now much more air and more aggressive timing, I just did the classic quarter mod. Costed me .25 and bumped my fuel pressure to around 14 psi. A quick note is if you have low fuel pressure and the motor sees you are running lean, it can cause the ECM to command more fuel to dump in, causing much much worse economy.
Fourth topic is the back end…. Exhaust.
The factory exhaust is extremely restrictive. I have a cat delete with an exhaust cutout. It’s loud but it noticeably increases mpg. Back pressure is not good. In another post I am doing an experiment with free flowing exhaust for economy, and how far you can get before popping an EGR code.
Fifth topic is the most important by far.
-Right foot usage. No matter how efficient you may make your motor, your acceleration will decide how you will do economy wise. Ease into the throttle and roll to stops. This will by far have the biggest impact on economy and hey, we all have old trucks, if we go slow people won’t honk, they will just angrily speed around.
Overall, besides that I just run synthetic shell Rotella 5w-40 and try to avoid stop and go, although city mileage isn’t too bad, it definitely isn’t nearly as good as parkway. Some future stuff I want to do is to take off the smog pump belt, I understand it doesn’t have much of an effect but I have no cat so no point turning anything more than I have to with the motor. Also maybe an electric fan to help reduce load, and probably a cheapo TBI spacer to help atomization of fuel, another polarized topic, but I’m curious to try it. In conclusion, many might see this thread as a sales pitch of snake oils, but it is what has noticeably worked for me and many mods have increased my power making this brick into a beast on the parkway. Do with it what you will but it is what worked for me and maybe will help someone else.
