Ramair21

iTrader: (3)

this is how it goes guys... im going to L.A. CALI to go see a friend about 400miles away from my house. well anyways i stop about 225 miles into the drive to fill up cause our gas gauges likes to tell lies, well anways i top off about 7 gallons. i do the math and i get about 32 miles per gallon. is this true???

azvolfan

when I bought my car and drove it to phx from Columbus, I got 28 mpg's on my trip. And I was not going slow. So it is possible.

Remember the LO3 was the economy V8. If there is such a term.

Ramair21

iTrader: (3)

yeah i know that the LO3 are good on gas but i was going about 75-80 miles per hr. and the tach read about 2500 rpm. so i assume that my little V8 is still strong. can anybody else top 32 miles per gallon??

dimented24x7

iTrader: (2)

Small, short duration cam, EFI, and HW mode = good fuel economy.

Fast355

iTrader: (2)

Dimented you forgot to mention tall gearing and good aerodynamics.

My fullsize van on the highway with a cammed carbed 305 got 20 on the highway. The TBI 350 gets 18-21. Take into account your car is lighter and is pushing less air you could definately have gotten 32 mpg.

dimented24x7

iTrader: (2)

Ah, yes. Also forgot the torque converter clutch lockup...

Fast355

iTrader: (2)

High swirl intake ports too.

Ramair21

iTrader: (3)

people didnt belive me when i told them. they were comparing my car to a honda accord getting the same thing. all i know is that numbers dont lie. and im very proud of my little LO3, it likes to suprise people if you know what i mean.

ShiftyCapone

iTrader: (7)

Stock LO3's are very capable of getting the same mileage as yours. 99% of all these cars on the road are horrendously in need of a tune up and basic maintenance that keep them in the 20's or worse. When my car had a cat-back and open element I used to get 31mpg on every trip with the windows down, stereo up, and needle at 75mph. These cars are great cruisers. We typically don't see that type of mileage because of our heavy right feet

NEEDforSPEED

TBI so many ways to boost your MPG but never the other way around to HP

90RS305

Yes, actually My last roadtrip from Utah back to AZ my car got 36mpg. When I filled up, I had already gone 411 miles on that tank and I wasn't even empty!! I love my LO3!!

Bruce (90RS305)

z71stroker

so it's bad if my L05 gets 10 city and 13 highway mpg? lmao. it's a 5500lb vehicle, but still.... geez - well atleast i don't burn or leak any oil, besides breather blowby, my foot gets stuck on the throttle sometimes.

Keith5

Ordinarily I would think that if you said you got 32 miles per gallon I would say that you were full of crap, but after last summer I believe you.

My friend and I went to the Charlotte car show. I took my cavalier and he took his L03/5speed/hardtop camaro. I ended up geting 35 miles per gallon. I couldn't really check his acurately because I didn't see how many gallons he put in when he filled up. He did remember how much he paid for the gas though, so I divided it back out and found how many gallons he put in.

ASSUMING that he gave me the right $ amount. He got around 30 MPG on this trip. It HAD to be in the high 20's at the least. We filled up at the same times, and an F-body gas tank is 1.9 gallons bigger than a cavalier's.

It's just crazy.

Fast355

iTrader: (2)

Thats bad considering that my 5,300 lbs brick was getting 18-21 on the highway and about 14-16 in town. I was averaging about 17 mpg. That was with a cammed and head 355 TBI, 700r4 w/(2,000 stall), and 3.08 gears. Can't wait to see what my ported TBI heads will get.

z71stroker

are you friggin serious? *goes and kicks rocker panel. son of a! but my L05 is the 210hp High Output L05, so maybe that's why? lol. well I have a 6" rod 355 with vortec and a 268h going in, 10:1 CR, was planning on going with a diff cam but i said screw it. Watch my mpg jumps back up to 15mpg like when I bought the truck 4 years ago.

dimented24x7

iTrader: (2)

There is. Its called heads and cam . But, since power is usually inversely proportional to fuel economy, your gas milage will suffer unless the head/cam combo is more efficient then the present stuff.

My fuel economy is so-so. Around 15 mpg in the city. Hopefully the vortecs im going to buy will boost the economy with theyre increased efficiency. Not only does the economy suck with my present heads (882 knockoffs), but so does the power. 0-60 in under 6 secs but after that its like I jsut threw out an anchor.

Fast355

iTrader: (2)

That is what my engine was too, the K vin code one with 210 HP and 310 ft/lbs that came out of a 1992 G20 Van. It had the 65 lbs/hr injectors and a small roller cam from GM too.

Gearing, state of tune, driving conditions, and the usage of the throttle pedal all have an effect on gas mileage. My engine is very volumetrically effiecient in the low-mid range rpm band and used tall gears with a moderate torque converter. It drives the same way now with the ported TBI heads instead of the HO 305 heads. If you were to ride in my van with me just pushing the pedal about 1/3 of the way like I usually do you would swear that I had a CVT transmission. I can literally push the pedal 1/3 of the way down and the engine sits at 1,900-2,100 rpm through all the gears, until the converter locks. I also have my closed loop air/fuel mixture stoich ratio set at 15.4:1 instead of 14.7. Basically being a 1983 I am able to get away with the slightly more NOX emissions(still much cleaner than the Q-jet) for the 1-2 mpg better that this gets me. I had also gone in a tuned my spark tables for the highest vacuum in the given cell. Took some time but well worth it. IMO the GM tuning is for someone that is a worst case person. GM has to protect those guys that will drive in Death Valley, with the A/C one, the radiator low, the radiator full of bugs, a bad fan clutch, poor octane, towing more than they are suppose to, etc. Therefore their tune is very mild and can be tweaked alot even with a stock engine. That is how I got my feet wet is on a stock engine.

I also have had the LT1 camaro roller cam which has less friction and a set of 305 HO heads that breathe better and have a smaller chamber giving a higher compression ratio and more effiecency at part-throttle.

Your cam is a little large for TBI but I saw a test where it makes like 16 in/hg of vacuum at a 650 RPM idle which is good enough to tune. You are going to need to burn chips or have one burned for this (it will cost you about the same $ but if you spend the time to learn how to burn chips and get the tune correct it will run much better.

z71stroker

i'm learning to tune right now. It was kinda funny, I booted up my buddy's lap top he let me borrow this morning, and I'm hooking up everything up with cool new interface cable that I made ( didn't work) to datalog to get my feet wet, and I look back to check the screen and i'm just like "WTF"!!!... it's in SPANISH! i think i said it out loud because the neighbor gave a dumb look and went back inside. I have 3.73's and a flat tappet cam though, it is K vin code though. Or I thought I had flat tappet, k1500. motor is in short block form, I can still pull the cam out - I'm just going back and forth wondering how much low end I'm gonna loose even with my compression.. since the vehicle is heavy

Fast355

iTrader: (2)

TBI heads and intake tract are so overkill with velocity anyway that a cam won't really kill too much low speed torque. Read the bottom of my porting 193s post. I killed a civic, up hill, at part throttle, using nothing but mid-range torque.

I also noticed that you have a Z71 which will always be a couple of MPG lower than the 2wd version of the same vehicle. Just due to the fact of the extra weight and more wind resistance due to the factory lift compared to the 2wd.

I would also recomend putting headers on the truck if you want the extra power and possible fuel economy gains. I was averaging 18 mpg with a carbed 305, swapped to the 350 tbi and got 15, put headers on and went to 17 but had alot more low-mid range power and similar HP.

My first cable didn't work either but it was because I installed the transistor backwards!

What year is you truck? Are you using WINALDL? You might have the wrong ECM selected.

To me it sounds like you have an exhaust restriction or something. But then again if you like to drive 80 for any time it will kill mileage especially with 3.73s. 3.08s are great for freeway flying though.

Here are some quick DD2000 numbers for a rough idea(Probably a little optimistic). Stock 193 heads, 268 cam, ultimate tbi mods, stock manifolds and exhaust.

RPM-----------HP---------TQ
2000---------124--------326
2500---------162--------341
3000---------206--------360
3500---------241--------361
4000---------267--------350
4500---------287--------335
5000---------294--------309
5500---------280--------267

This is assuming properly tuned and the ability to deliver the correct amount of fuel. Notice how the horsepower stops climbing at about 4,500 (shouldn't be a problem due the the 4L60E shifts at about 4,600)

Fast355

iTrader: (2)

Just saw you were going to run vortecs. Add about 10 ft/lbs through the powerband and 25 HP.

RPM------------HP------------TQ
2000----------130-----------342
2500----------170-----------357
3000----------214-----------374
3500----------250-----------375
4000----------278-----------365
4500----------301-----------351
5000----------312-----------327
5500----------303-----------289

Thats not even with headers.

Keith5

My Full Size Long Bed 2wd has the 210HP 350. When it was new it got 18mpg average. like 22 Highway(with camper).

It's got 200,000 on it now and without a camper it's averaging 16 to 16.5mpg overall.

Keith5

I love when you can add power AND gas mileage. I've done it on my firebird. I dropped over a second in the quarter, and also gained about 3 MPG.

Cadillac

I'd love to hear the details.

Keith5

Same thing everybody else does.

LT1 cam, TPI 305 heads, hooker headers, hooker catback, catco 2.5 inch cat, AC Delete, Smog Delete, Open Element, took the wrap around spoiler off, speed-o-motive underdrive pulleys, timing set on 8 degrees, heater core valve delete, MSD 8.5mm plug wires, stock delco plugs set at stock gap, made for you plug wire separators, Conrad cap and rotor(brass inserts), edelbrock tbi intake, 3 angle valve job, port matched intake and heads. .. . .


I think that is it, how is that for details? I included everything. I'd say that some reduced weight along with better spark and less restriction has a lot to do with gains in power and efficiency.

z71stroker

well see my right foot has around 50lbs of lead strapped to it, so i'm inherently flawed to be either idling or WOT, i prefer wot btw, but if I had a itty bitty right foot and just putted along, I might get 14 mpg lol.

Keith5

If I'm rough on my truck I still get 15.5, and I get 20+ in the car being rough on it, plus a night of drag racing on the same tank.

SB406

I toatlly agree. My 1/2 ton van was getting 20.9 mpg highway with a 406 in it on untuned 350 TBI & RV cam. I see no reason why a L03 couldn't surpass 30 mpg.

white91bird

i seriously thought my car was worse/...somebody have anything to say?

AJ_92RS

For a short time when I started a job ~45 miles away from my house my '92 w/190K miles on the clock did fairly well.

With about 8 stop signs and three 35 mph zones on the way I would average 26 mpg. That was also with the 1/4 panel bashed in, two rear tires out of balance, in need of a front end alignment, always dirty, and the weight of my 240 lb. butt in it.

I just kept it under 2000 RPMs at all times. Not easy to do, but do-able.