Just a gas mileage question with perfomance engine!!

[Guest traub83]

Do you guys think it would be possible to build a 350 chevy motor, get it to crank out over 500hp and be daily driven and get pretty good mileage like around 15-20mpg?? My neighbor told me he done it with his corvette I didnt call him a liar I was just amazed honestly cause I think I remember car craft did something like that but just seein what you guys would say on it. Id love to build a 600hp monster and get 20mpg out of it lol...

[Guest tony78_280z]

My goal has always been about 300-350 horsepower (before NOS) that gets 20mpg. I choose 20mpg because it is the best milage my Z ever got before the swap, so I can feel it is justified. Where as I'm not at the 300hp I am closing in on the 20mpg.

 

An overdrive tranny, strong ignitions spark, adjustable vacuum advance, and a small carb with stronge booster signal realy helps in the gas milage area. My last mgp run I estimated at 17mpg, but I have made considerable improvements since then. I got new plugs and wires, I found a vacuum leak and got my vacuum advance set up. (Both at the same time! as my old advance canister was leaking) I'm still working on gettin my torc converter to lock up (details here), and that will help alot. For my last few MPG I'm gonna have to play with aerodynamics a bit.

 

As for Horsepower, I'm looking for good flow without changing my cam (much). I'm saving up for vortecs. Once I can get 300-350hp relaibly out of my motor, Then I plan to run a 100 shot of NOS which will put me at 400-450hp.

[Guest zfan]

ROTFLMAO! My Z gets maybe 8-10 around town and 12-14 on the highway. Fuel economy, what fuel economy! I only wish!

 

Mike

[Phantom]

My 280Z averages 19-20 commuting to work.

[DaleMX]

You can do it, but it won't be a carb and 4 speed transmission car. You gotta go FI and overdrive.

[Guest traub83]

So basically run a t5, t56, or a 700r4 with a fi setup like the accell setup or that edelbrock FI setup correct?? or heck even a TPI setup.

[80LS1T]

You can do it, but it won't be a carb and 4 speed transmission car. You gotta go FI and overdrive.

 

Hehehe tell that to the moron at work who thinks carbs are still better than EFI in every way:twak: . I try to tell him that cars are tune rich from the factory but he just wont believe me. He thinks EFI is nothing but a gas hog and that all cars should be running carbs.......of course he thinks his 1979 Chrysler New Yorker with its 318 is fast(at 15.7@ 89mph in the quarter mile)

 

I just tell him ya you go adjust your carb while im driving around and letting the computer make adjustments on the fly!

 

I dont know if you can make 500HP and get 20mpg but as Phantom said hes getting 20mpg and hes putting 300HP+ to the ground witht he LS1/T56 combo, thats a good start!

 

 

Guy

[Lewis Maudlin]

My 400 hp at the crank 355sbc only ever got about 12mpg on average with a 700R4 overdrive tranny and a 3.54 rear end. I have opted this time to go with a SR20DET which I am in the process of installing. I should be able to get 30 mpg at 7 psi boost and 255 hp at the wheels at 15 psi. The best of both worlds. I can get more than 300 hp at the wheels if I switch the MAF injectors and computer, however, I won't be able to get 30 mpg the rest of the time.

 

BTW, with the 250 lbs or more weight savings for the aluminum blocked 4 cylinder, the SR20DET should run a quicker quarter than the 400 hps sbc.

[Guest tony78_280z]

You can do it, but it won't be a carb and 4 speed transmission car. You gotta go FI and overdrive.

psst... a 4 speed automatic is an overdrive.

 

And, I accept your challenge. As I posted I will get 300-350hp with a 100shot of NOS putting me at 400-450hp. I will also regularly get 20mpg. Of course it'll be awhile coming, so It'll take me some time to prove it.

[DaleMX]

Yea, I meant manual tranny without OD. If you really tweak it you might get it to work, but FI is so much easier and has a huge performance potential, not to mention the computer compensates for mountian driving, cold weather, hot weather, has knock retard built in, oh and its computer tuned so you dont have to change jets, you just reprogram on the fly with the LS1 stuff.

 

For what it's worth, I took 2nd and 3rd to 6500 today and it pulled like a freight train to 100 mph before I knew it. Makes me wonder how long the stock rear will last if I get on it a bunch. I gotta go to the track and see what the modified LS1 can do. It pulls so hard you have to really concentrate on the tach and the road to say in control.

[SSflyer]

My 99 Camaro dynoed 365rwhp and the last trip from Phoenix to San Diego averaged 33mpg. The best leg was 36.6mpg. I've got the same engine set up going into the Z, so with the weight reduction (but higher gearing) I hope to get the same.

[Guest FasterbyFosta]

Do you guys think it would be possible to build a 350 chevy motor, get it to crank out over 500hp and be daily driven and get pretty good mileage like around 15-20mpg?? My neighbor told me he done it with his corvette I didnt call him a liar I was just amazed honestly cause I think I remember car craft did something like that but just seein what you guys would say on it. Id love to build a 600hp monster and get 20mpg out of it lol...

 

I know its not a chevy, OR a datsun, but a friend of mine has a 600+ (dynoed) hp 68 mustang (not sure on the year..) that got 28 mpg driving from here to LA and back again.

 

It has a 408 with a Novi 2000 blower, DFI, an AOD trans and ran a 10.001 in socal on that trip. He drove the whole way on pump gas and street legal slicks to boot...

 

So it is possible, but I agree with most the other answers, only with Fuel injection.

 

On a side note, my 400 hp carbed chevy got around 15 mpg in my Z (3sp auto) and my 450 hp 396 lt1 got around 20 mpg in the z with a very rich tune...

[Guest ZagatoZ]

ok... i know i read an article in an American muscle car mag, either hotrod or chevy HP about, i believe it was a 500hp motor, getting 25 mpg. Thats about as detailed as i can get lol sorry, but i would say YES! it is possible. Not very hard to do either from what little i remember. I know for sure the motor was EFI and im only 50 % sure it was NA. Might have been a 400sb.... Hell, i will have to go look for the article now!

[Guest Nikolai]

The LSx truck guys are pulling down 20+ with 6.0's and turbos. I would think there is seriously something wrong if you can't do that with half the weight and 10x better aero-dynamics.

[Guest traub83]

zag that may be the same article I was thinking about cause it sounds about what I remembered also..

[BrandonsZ]

I am happy to report that with over 300hp, running 87 octaine, 10 deg BTDC at idle (vac advance temporarily disconnect) with a 650cfm edelbrock AVS 4-bbl carb, 350cid, T56 6-speed manual .50 6th with the 3.36 stock rear, I get 25mpg hiway. The car got 18 hiway with the original engine (2.4 with 4-speed I believe it was 1:1 4th). Adding this drivetrain lowered the car .5" front and .5" rear so I think it must have been at least 200lbs heavier, I wish I knew, but it feels a little stiffer and handles better IMO (jtr position). ~1500rpm @65 in 6th, and plenty of torque to spare.

[strotter]

And *I* am happy to report a vortec-headed-conventionally-aspirated 350 with T-56 and 3.36 rearend I got 28.9 mpg (once) while cruising in 75-85 mph traffic on the freeway, including a couple of spirited moments when a 300ZX was next to me (briefly). Fuel control by Holley 670 TBI & 7747 computer, highway mode disabled. HP in the mid-300's, 1/4-mile 12.96 @ 109 as reported by my little G-Tech. (Yes, I'm burning up my tires in 1st. Sue me).

 

However, around town and on my daily drive to work (which is mostly country secondary roads with lots of intersection stops) I have only once gotten even 15 mpg, and doing so involved my driving - well, OK, I'll say it, FIFTY-FIVE MILES PER HOUR for several days in a row. SEVERAL DAYS! AARGH! This is driving me nuts as I, too, am trying to at least match the L24's economy (in the high teens for this same drive). I'm installing a Stealth Ram here in the near future, which (along with a '7730 computer) will give me considerably greater control over my tune.

 

About the aerodynamics of the Z: you've noticed, of course, that the thing is a barn door at speed, haven't you? I mean, pull it up to 80 and clutch it and you'll be going a legal-fast right quick. It's like the emergency brake is pulled all of sudden. My Dodge Intrepid will, if thrown into neutral at the same speed, coast from here to L.A. and back. Aerodynamics 1960s vs 1990, no contest.

[Mikelly]

Yup, It can be done, and Yup, Stotter is right. These cars look sleek... But aren't!

 

My 99M6 C5 vette was knocking down well over 27mpg regularly with 335/353 to the wheels and with my lead foot...I expect to get close to that with about 80-100 more HP at the wheels with the new motor. Had a Mustang GT with a bunch of bolt ons and a T5 that was consistantly knocking down 26mpg with the wife driving. EFI is the only way to fly, and the most efficient!

[BrandonsZ]

Considering gas prices, I'm glad I get better gas mileage in my 240z hotrod than my 240 Volvo.

[Alf]

I have a 69 camaro with a 355 it has a extreme energy comp cam .490 lift, flat tops, msd 6al, roller rockers, edelbrock performer rpm intake, 67 chevy double hump heads ported 3 angle valve job, i have run a best of 12.82 at 108 and i have calculated it to be right around 425 hp and i get about 15 mpg and thats with 3.73s and a muncie no overdrive.