I drove back from Richmond to Durham yesterday and got about 25 mpg on the trip back. This was with 92 octane and the car temp never got to 160C because it is friggin cold up here and I haven't turned off both my fans yet. I was doing about 70mph @ 2550 rpms. Not too bad.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

-=ICON Motorsports=-

 

You got 25 mpg on the highway with a carb??? That is frigging good, man.

Whatcha running for carb/intake/cam/heads/and rpm at your highway speeds???

 

Pretty much says what my engine speeds and stuff were.

Q-jet/Performer intake/ 64cc Performer heads/ 350+0.040 ci/ TES exhaust/ Comp262 grind w/ 1.6 roller rockers/ 3.27 9-bolt/ 700R4 w/ 3000 rpm stall...

 

NO way you got 25 with that, man... heeeeeeeeeee, heeeeeeeeeeee

 

I believe it. I get 20 on a constantly rich Holley/oil burning engine.

On a more efficient engine, with a Q jet, 25 is very doable. Still impressivce to actually hear though

 

I got 22+ on the way home from Charlotte a few months ago and it was hot. I even had to run the heat/vent to keep my temps down the whole way home! The gas milage was the only good part of that trip home.

That is my biggest thing about all the new Nissan and rice cars that claim like 220HP, slow *** 1/4 times, and look at me with 350+HP and low 13 sec timeslips and say they get better milage then me. Bullcrap, they only get 24 or so on the highway too. They are thinking that an engine like mine has to only get 10 mpg. My biggest complaint is the small 13gal gas tank...

 

I get 22-24 mpg as well - highway. Around town is more like 10 mpg.

Biochem - the capacity of your tank is 16.2 gal BTW

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1985 Z28, Jasper Class 1 350, Edelbrock Performer intake, Dual snorkel air cleaner, K&N, Edelbrock headers, Catco 3" cat, Hooker 3" cat-back, Richmond 3.73's, Transgo shift kit, JET Stage 2 chip, Hypertech coil, Lakewood LCA's, Powertrax locker, SSM subframes, Centerline Auto Drag's

 

You must have a differnt tank. I just filled up this morning and I only got 11.2gal in there and I was almost on Empty. The most I have ever gotten in there was about 13.2 gal... Maybe I just have so much crap in there that it is taking up space in the tank...

 

Are you CARB guys turning about 2000rpm on the highway with a lock-up converter? I usually use Holley carbs (not QJet, like you) and was under the assumption that in OD and lower rpm, like 2000, you would activate the power valve circuit most of the time on the highway and kill gas mileage, like down to 12 or so. Maybe the QJet doesn't have a power-valve type circuit? I'm a Holley and EFI man, myself, so i don't understand QJets much.

Can anyone enlighten me as to if QJet (vs Holley) would give better highway mileage and why??? Don't care about city mileage talk... Also, are the Edelbrock QJet carbs functionally the same as the orig QJets? I have installed 2 of those Performer RPM QJet carbs for guys and did not hear/ask for their mileage results...

 

Since this is turning into such a love-fest, i have to admit i've gotten 26mpg in my old Z with a little more cam but less stall and gear.
Even my 83GP turned in 20mpg this weekend going to my parents, not bad for brick-wall aerodynamics and no-OD.
And you're exactly right biochem, i just laugh when you look at the mojority of todays 6 banger imports, even some of the 4s when they are only rated at low-mid 2os on the highway. Pretty sad that CCCS can beat it on a big inefficient 50 year old engine design.
...ed

 

Oh yeah, i forgot to add, your gas tank is 16.2 gallons. Just because your guage reads almost empty doesn't mean squat. Gas guages are the most inaccurate instrument ever installed in a car.
...ed

 

The electronic feedback carbs aren't as susceptible to the low RPM problems as are their mechanical open-loop predecessors. For what it's worth, I went on a 700-mile round-trip to Nebraska two weekends ago, bucked a head wind on the way back. This is a mostly stock but getting tired LG4 with a non-functioning TCC, and I averaged 27.6 for the trip. RPM's were about 1950 @ 65, 2100 @ 75, right at 1900 @ 60, at least 200 miles at each of these speeds. I get around 20 mpg commuting, although you said you don't care about that.

The '57 only gets about 13 mpg. Generally speaking, the Q-jet will get better mileage than a similar flow square-bore. The Edelbrocks are funtionally identical to mechanical Rochester Q-jets.

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 2.73 open. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

[This message has been edited by five7kid (edited October 15, 2000).]

[This message has been edited by five7kid (edited October 15, 2000).]

 

And to add to what five7kid said, even with the older mechanical QJets you aren't going to dip into the power valve circuit until you are below about 6-8" of manifold vacuum. Look at the average 350's engine vacuum cruising 60 MPH at 2000 RPM and I think you'll be surprised to see over 13" of vacuum, asuming a near-stock cam and a decently aerodynamic body.

 

Thanks for the replies, guys...

Have a nice weekend!!!

 

I get 16 highway in my Firebird and 11 in my Grand Prix, does that mean I can join the party? lol...well I KNOW the reason I get bad mileage in my cars; both have a double pumper holley on them


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Nice car: 1988 Formula 355, mildly ported/polished Vortec heads, RPM intake, Comp Cams Extreme 268 cam, 650 Holley double pumper, 5-speed/3.73 Richmond gears, and N02 on the way
Old 1/4mile: 13.5@105mph

Evil Car: 78 Pontiac Grand Prix, 500inch caddy motor, edlebrock intake,HP Holley 750 DP race prepped carb, B@M TH350 tranny, 16inch Iroc-Z rims, blacked out chrome, soon to run 10's...

There's no replacement for displacement!

 

LOL....I'm sure the 500ci in the GP and the big *** cam in the Formula have NOTHING to do with the poor mileage

 

I consider 25 to be on the low end of my milage. I usally get 27-28 on my factory Qjet auto LG4 with 200,000 miles.

BTW, used to live in Durham (Bahama), but I drove from Georgia. I never could get the thing to pass emisions there so I kleft a GA plate on it

Joey

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1986 Black/Gold LG4 Z28
Original Owner, 200,000+ near trouble free miles.
Mostly Stock.

1995 Dark Red Metallic Corvette Coupe Original Owner

 

How often do you all change the O2 sensor? In my experience with EFI cars it has a big impact on fuel economy and emissions when it degrades, but I don't know how important it is for feedback carbed cars.

My brother recently got a stock '86 Camaro Z28, so I'm hoping to learn more about it (and maybe drive it occasionally)

Brian

 

on thw way to new york A few weeks ago, i got 28 to the gallon with a carbed 350, performer intake, crane cam, and five speed trans. did about 65 at somethin like 1850 rpm. no, relavence here, just my two cents...

 

Is that a computer controlled carb??? or a "regular" no-wire carb??? "What carb/cam are you using" are better questions?????

[This message has been edited by FastBroker (edited November 17, 2000).]

 

ZUPman, any reply to my last post?

 

FastBroker,
sorry for the delay, i havent checked here in a while, anyways its a non comp. q-jet and the cam is a 272 degree duration