better mileage

[vortec]

82 k5, 350 w/qjet. i know this combo, plus weight and bad aerodynamics equals less than great mileage. but, i know somebody on here has some tricks to grab at least 1 or 2 mpg. hey, when you get 10-14mpg, every bit helps. my friend likes to take trips to moab in his 2.5L jeep. that's 1000 miles (ton of $$$) each way for us. he wants me to take the k5 too and swears he's only getting 12-14mpg. the only way i believe that is i've seen the jeep struggle to reach 60 on the highway, while my k5 will easily top out the speedo in the same situation (85-90mph). but he has to get better low speed mileage than me, i figure.

anyway, my point is i'd appreciate any hits, tips and tricks you guys have to offer. i keep my '94 xcab 1500 running 18 city, 26 highway, so i have faith i can squeeze a little more out of that blazer. i just don't know as much about it yet. i'm not against pulling emissions stuff, within reason, if it will help. i do have to pass inspection in a few months, though.

thanx

 

[BIG*RED]

i have an 82 k-5 also, and despite what many think, pulling your emissions crap won't really free up any mpg..there is the usual stuff, free flow exhaust, free flow cat, open air cleaner, re-gearing the rear end, running a smaller cab, i think my q-jet was a 750cfm or maybe a 700 cfm..you could go to a 600 cfm..which is plenty for a small block..

but 10-14mpg is good mpg..you could be in my shoes... i have a 350H.O, 10.3:1 compression, 800cfm carb(yes i know thats a lot of carb for a 350) only runs on 92 octane or higher and i get about 3.8mpg around town and about 6mpg on the highway..

if i got 10mpg i would be happy

oh and i live in cali and when i first put the engine in, i ran it for a year with no smog crap, no pump, no cat, nothing. i have since put it all on cause i had to get it smogged and there has been no change at all in my mpg from haveing it all off to putting it all on..

 

[xtrmjoe]

If you have done all the regular eng mods to get better gas mileage the only thing left is to lighten it up. The less weight you have to push around the better. The back seat alone is a heavy sob. Carpets, ac, dash, ft fender wells, anything you can live without rip off.

 

[dyeager535]

First off, a 750CFM Q-jet will have smaller primaries than a 600CFM squarebore carb...better economy with the Q-jet right off the bat. If you stay out of the secondaries, you can get good mileage with one.

Is your 10-14 combined city/fwy? If so, IMO, without a diesel, that is as good as you are going to get. That's exactly what I get city, and my best ever freeway was 18MPG. That was perfectly flat ground, 55MPH, cool night.

The truck is a pretty petite (for these things) at 5000lbs, you'll have a hard time getting one of these trucks under that weight without removing comfort items.

Since you can get good mileage out of your other rig, it doesn't sound like your driving style is the problem, but just in case you drive it differently than your other vehicle, using cruise control if present, driving as slow as possible, and not running up to stoplights (if you have to deal with as many as I do) will all contribute measurably to economy. Make sure your plugs and wires are in good shape, make sure the distributor innards are good, make sure the carb isn't running rich, etc. All basic "tune up" stuff, but +1-2 MPG should be attainable, just not likely if measuring city/fwy.

 

[Jeff427]

Something a lot of people overlook for improving gas mileage is reducing rotating weight. Look for some light weight aluminum rims and run lighter weight radial (compared to bias ply) tires. My brother did this with his '70 Scout 800 with a 196 4 cylinder and 3.73 gears, and he says is drives like a completely different Scout. Better pick up, takes off from stops much better and better gas mileage.

 

[dirtwarrior17]

rotational mass is a huge part of mpg and rwhp.... a bigger disc brake kit will rob 15-20 hp at the wheels. if your running something like 35x16 boggers and a mild motor then 3.8 mpg around town should be expected. either way you will have to compromise for offroad performance or mpg. Most of the lighter tires are crap tho. There are a few like the mud terrains, big foots, etc that are light and can hold there own on the dirt tho.

 

[rjfguitar]

rotational mass is a huge part of mpg and rwhp.... a bigger disc brake kit will rob 15-20 hp at the wheels. if your running something like 35x16 boggers and a mild motor then 3.8 mpg around town should be expected. either way you will have to compromise for offroad performance or mpg. Most of the lighter tires are crap tho. There are a few like the mud terrains, big foots, etc that are light and can hold there own on the dirt tho.

A disk brake conversion will only help mileage because you are not turning a heavy drum and shed weight with the disks. The original poster was not the one getting 3.8, that was the next guy down.

Not only that, but 3.8 should NOT be expected with anything less than a blown 502 with 44" boggers. I've got 35x16 boggers and a warmed over carbed 406 and still lay down 7-9 in town.

 

[rjfguitar]

To me it sounds like you are getting pretty decent mileage for a carbed V8 4x4. Like Dorian said, that Q-jet is basically as good as it gets before fuel injection and most of us have a hard time laying down that good of mileage in the first place. 10-14 is not bad at all and is what most carbed K5's get when stock it seems, and are in good running order. Heck I've heard of stock K5's with terrible gearing and a rough running engine have a hard time climbing out of single digits.

Opening up the exhaust and air filter will help maybe 1-2mpg but for what those mods cost, it would take a LOT of miles to make that up from gas savings.

 

[dirtwarrior17]

no you missed that one... I was saying if you start out with disc brakes and then add bigger disc brakes you will lose 15-20hp depending on the size. If you take that into consideration for tires, a heavy bogger will kill your gas mileage, as well as rwhp, and take you down to around 3.8 in the city... i know he wasn't the originaly poster.

 

[rjfguitar]

no you missed that one... I was saying if you start out with disc brakes and then add bigger disc brakes you will lose 15-20hp depending on the size. If you take that into consideration for tires, a heavy bogger will kill your gas mileage, as well as rwhp, and take you down to around 3.8 in the city... i know he wasn't the originaly poster.

I have never heard of a "bigger" disk brake mod. You use 3/4 10B/44 rotors and calipers. Even if there was a bigger option I HIGHLY doubt it would cost 15-20 MORE HP over the normal disk conversion, infact I bet it wouldn't make hardly a bit of difference at all.

A heavy bogger will not take someone from 10-14 to 3.8mpg. 3.8 should NEVER be expected with anything less than a blown 502 and 44" boggers.

I DO have experience on this one. When I went from a 33x12.50 BFG M/T to a 33x14.50 SSR I dropped about 1-2mpg. when I went from the SSR's to 3/4 axles and 35x16 boggers (more lift also added at this time) I dropped maybe another 2mpg. Thats not even CLOSE to 3.8.

 

[dirtwarrior17]

actually that was straight from speed channel on a rw dyno where they lost about 10 hp with bigger disc brakes.

I DO have experience on this one. When I went from a 33x12.50 BFG M/T to a 33x14.50 SSR I dropped about 1-2mpg. when I went from the SSR's to 3/4 axles and 35x16 boggers (more lift also added at this time) I dropped maybe another 2-3mpg. Thats not even CLOSE to 3.8.

if you went from stock tires to 33's you probably lost about 1-2 that would be around 9 or 10 in city mpg then you say you lost another 1-2 mpg when you went to wider 33's then you bolted on boggers and lost 2-3.... add it up. the guy that said that was running an 800 cfm carb. depending on how it was driven that is not that hard to beleive.

 

[rjfguitar]

YOu have a LOT to learn obviously. I gained mileage when I went from stock tires to 33's because I also went to 3.73's over the original 3.08's then. Like I said, I lay down 7-9 in town. You are not going to convince anyone that 3.8 is about right for anything less than a blown 502 1 ton on 44's.

 

[dirtwarrior17]

lol............. what would that be without the gearing swap and an 800 cfm carb? hmmmmmm around 4 mph in town on a bad day.

 

[rjfguitar]

lol............. what would that be without the gearing swap and an 800 cfm carb? hmmmmmm around 4 mph in town on a bad day.

You have a lot to learn. A quadrajet has the capabilities of flowing 795 CFM but only does it called apon. That would be why they come factory on stock 305's. The great thing about a q-jet is it has small primaries and large secondaries, the primaries are smaller than what a 4 barrel 600 square bore has. This design delivers the best mileage a carb can deliver.


As to the quote, I don't know what you are asking. I get 7-9mpg with a mild 406, 4.10's, and 35x16 boggers.


How about some opinions from the outside world here guys........

 

[mxfireman]

hey rif what about dropping the mechanical fan for an electric? Will cost some $$ but that's a way or dropping the smog pump and put it back on when inspection time comes?

 

[rjfguitar]

If your fan clutch is working properly I doubt it is using much more than 10HP on a steady basis. For the money (I spent $350 or something on my dual fan kit) I don't think I'd do it. THat smog pump doesn't really take much power either. I found the smog pump belt loose as a goose one time and it never slipped or squeeled so obviously it doesn't pull very hard. It's just a little air pump anyway.

 

[beater_k20]

actually that was straight from speed channel on a rw dyno where they lost about 10 hp with bigger disc brakes.

excellent argument, "i saw it on TV"

oh yeah, you're being "that kid" again, please knock it off. just like a damned little Tim Jr.

 

[dirtwarrior17]

beater stfu..... you don't know me or what im talking about.... these guys had absolutly no connection to any sponsors and why the hell would they lie about losing hp....


funny how you are the only one saying these things.....

 

[AkMudr]

3.8mpg MIGHT be expected in a souped up stroker motor or something blown, not a mild 350 with 35" boggers. And if you are getting 3.8 youve got serious tuning to do.

 

[dirtwarrior17]

dude why the hell are you even arguing with me im not the one that said i get 3.8 i said with heavy ass tires and a 800cfm carbed motor that, runs a little rich will get 4 mpg in town DEPENDING ON HOW ITS DRIVIN. must have missed that part....stop trying to make yourself the god of everything. I have been dealing with q-jets for 5 years. you don't know everything ****. The whole time i've been on this site i have never heard you say your right im wrong to anyone.... I'm sure there are PLENTY of people who would agree.