Which of the above will give me the best power/mileage ratio, with the below build. I am looking for a minimum average of 20mpg. Emissions legal. Plans 350 block ZZ4 cam (possibly crane compucam 2032) Aluminum L98 heads or AFR's... probably l98's SO much cheaper Super ram setup 1.6 RR What setups do you guys have and what kind of mileage are you getting? I realize the smaller I go the better the mileage, but I want to see the differences to get an accurate idea of what I will get me where I want to be. James

With my old peanut cam/ 3:73s and a 700R4 and a GM Goodwrench 350 with full exhaust I could get about 18mpg, 20mpg if it was straight highway miles, running a 600 Edelbrock carb.

smae engine as mark with a tbi and exaust. I get around 23-25 mpg with mixed driving (city + highway) with "normal" driving. If i have fun and use my lead foot then it drops to around 17 mpg.

I can get 17 city 20 highway but usually 10mpg city.

Forgot I also have a non lock up converter.

Thanks guys. So far we have had TBI and Carb replys and since I am going MPEFI, I think I should expect around 10-15% better gas mileage than carb or TBI respectively. Does that sound about right?

Right now I get 12mpg with my tbi 305, but that is because of multiple problems.

Anyone out there with a 350+ making better than 15mpg city?

James

PS I forgot to mention I will be going with 3.23 gears, 700R4, Carbon fiber driveshaft, and I am going to try to lighten the entitre rotating driveline as much as I can to give a better crank to rear loss ratio.

GlennL98GTA gets 30mpg in his 350 TPI I believe it is, maybe try to PM him.

With my 355 (Ported 180cc Iron Eagles, 218/224 cam) a TH-2004R and 3.42's I get about 17-18 mpg in my Cutlass. With some tuning I know I could probably pick up a little bit. It's TPI by the way.

350 tpi- stock heads, cam and intake. Knocking down 25mpg on the highway

305 all stock got 18 mpg straight highway. 406 on same chip on same trip got 20+. Mild cam, TPI, SLP 1 3/4 headers, hi flow single cat, 700R4, 3.23 gears, 255/50R16 rear tires.

So your 406 got better mileage than your 305? Explain to me how that is possible... You have over 100 more cubic inches

James

Both my combo now and my dad's new combo are getting over 20 mpg on the highway. I'm getting about 16 in the city. With the ZZ4 cam and L98 heads I had previously, 25 mpg on the highway was pretty easy, even with the stock chip. Now that I know how to program chips, close to 30 mpg should be attainable.

You know where to find us in SoCal.

Hi Kevin,

I will need that PROM probably sooner than later. I am putting a deposit on the engine tomorrow and will probably be buying the entire setup... I just need to talk to him about it. Right now there are the IRON l98 heads and they need to be worked over as well. Shoot me an email and tell me what your schedule is like. If we can work out 300hp and 30mpg, I will be very happy.

James

It just worked out to the right combination. Heads have 170cc intake ports for good flow, cam is mild for increased low end torque, intake was opened up from twisted pipe with a stock canister to a straight 3 inch tube with an open K&N, exhaust went from stock iron manifolds and stock cat to SLP 1 3/4 with hi flow cat. Tires increased one size, from 245's on the 305 to 255's on the 406 (pressure same on both sizes at 28-29 cold). The injectors are larger, but chip is the same. The motor was professionally built by a local automotive engineering shop who do a lot of stock car engines and have years and years of experience. The distributor is the same on both engines but the plugs and wires did change. 305 had original plug wires with split fire plugs. The 406 has ACCEL 8.8 wires with ACCEL shortie header plugs. The plugs are showing an ash white color, so not too rich. It boils down that I am making enough power with less throttle opening to move the car. The trip was 200 miles non-stop gasing up at the start and end at the same stations. When filling up, I keep working at it till I can't get anymore fuel in. It should be pretty close on the amount of gas used, but at 200 miles and at 18-19-20 mpg, it's only 5/10 to 7/10 of a gallon to increase 1 mpg. Part of the increase was from the larger tires, but I did calc that in. Even if I used the same amount of gas, the larger tires carried my further so it cost zero gas to go further.

i get 8 in the city
i dont know highway
when the primaries are open it is a safe bet to bet that the secondaries are open too

BlueTA sounds like you really do have the best of both worls congrats That is what I am looking for.

I get 16-18 MPG in the city and have gotten 25-28 on the highway. The 28 mpg I have got several times during a steady cruise of 75 MPH on a round trip of 365 miles on one tank of gas.

quick rundown: 350, ZZ4 cam, edelbrock heads, T56, accel base/runners, speed density, custom PROM.

I get better gas mileage in the city by going 1-2-4-5or6 because it forces me accelerate slower as I go into 4th. I couldn't get over 22 MPG with a MAF setup.

check out my sig for more info.

took me two tanks to get from phila pa to ocean city nj..... about a 90 mile drive :lala:

That's what 5mpg at the most. HOLY CRAP.

HOLY CRAP!!! that's BAD!!

I couldn't live with 5mpg, I hate to be without 25 lol But if your whole intention is to be king of the quarter mile than 5mpg is better looked at as 20 runs Marshall89ws6, what are you running in the quarter?

I am not looking for N/A 11's, though ATI procharger is planned for about a year out. Best way I have seen to create power and not adversly affect gas mileage to greatly.

James

I have a 350 with the aluminum L98 heads and an LT4 cam. I'm getting around 15-16 city and 20-21 highway. Kevin91z burned my chip for me, and his dad built the engine.

i ran a 10.9 last weekend spinning everywhere still not used to the new clutch....... i use about 2 gallons just for the quarter........... and the firechicken isnt my daily driver

my 383 gets 25 on the highway. i have a street avenger and a th-400. its got power forever. ive got one hell uva crower cam in it to. ive also got 27 inch rear tires.

Well, with the tune in good order on my setup (see below) and Highway Mode enabled in the PROM I could pull right close to 30mpg with my setup when it had the 700R4 in it..... Should be able to pull over 30mpg on the highway with the T56 in it now, but I also recently swapped to the 730 ECM and haven't gotten the rest of the tune comfortable enough to re-enable HM yet.... So we will see how it goes.

I have an L98 with Corvette heads, HOT cam with stock 1.5:1 rockers, out of tune holley 750, dual plane intake, T5 and 2.73 rear. At 70mph I turn 1700rpm and get 26mpg, probably running lean. In the city I get 14mpg.

In the '92 I average over 20 (21 recently) and get 25ish on the highway.
In the '88 with 3.73 gears averaged 17 and could squeek 21 maybe on the highway.
Cars' info are in the sig.

I recently overhauled my 86'T/A and put in 355/4bolt, It gets on average 20mpg city and 24-25mpg hwy. It contains my dream power plant that I've wanted to do since owning it in 1989. Here's the list of goodies, TRW flattops forged, Total Seal Rings, World Product Torquer's 170cc intake runner for street 2.02int/1.6exh. I polished and ported myself. Ported and polished and matched stock TPI plenum,runners and intake base. Gutted the MAF, Put in TPIS "Fast Pack"(includes Air foil, adjustable fuel psi regulator, donaldson air filter, bosch platinum 4's plugs, and spiral core wires) Cam is from Summit Hydraulic flat tappet .488int./.510 exh. @114*centerline for good vacuum., 1.5 stainless crower roller rockers and edlebrock 15/8 headers with gutted cat going to flowmaster muffler 3" inlet and dual 2.5" outlets like factory. Running my fuel psi @ 43psi and adj. my timing with vacuum gauge till i got peak vacuum 18" and backed off 1" to perfection(old school of tuning). Replaced wore out under cap coil with 53,000volt from summit and holley module to allow rev up to 6,200. Though I do not run it that hard because peak h.p. is at 5750 and pulls to a whopping 400+ft/lbs torque from 2,000rpm to 5750 lays you in the seat like ole big block of yesterday(refering to my ole 69 ss396 4 speed). TPIS burned a custom level 4 prom that handles the particulars of management. It runs flawlessly and sounds awesome. Idle just turns me on. Rear wheel dyno with 245/zr16's @ 27" going thru modfied 700r4 with upgrades to 3:27 disc brake rear end netted 389h.p. at 6,000 rpm and peak torque of 435ft/lbs at 3000. Best run 1/4 13.4 @107mph.

Wow tigger,

Nice ride. Why did you go with the worlds over say the Aluminum L98's?

James

This is what I have, and I get 9 mpg.

383 stroker TPI (Tuned Port Injected)
10.2:1 compression (hypereutectic Federal Mogul pistons)
76 cc combustion chambers, 1.94/1.50 valves
Crane 2040 CompuCam and lifters
SLP runners
Accel 1,000 cfm throttle body
New Holley adjustable fuel pressure regulator (42 psi)
Bosch pintle style 22 lb/hr injectors
Custom chip by Motorvations in Tennessee
1LE aluminum drive shaft
700R4 transmission
2,500 stall converter
3.73 posi rear-end

I have a ton of torque, 1.92 60' times, but 14.6 best ET. It's fun to screw with the rice burners though.

I didn't really build it the way I wanted to, it blew up on me within 3 months of having the car, previous owner over tightened the rockers, wiped out 7 lobes on the cam. So it turned out to be a cheap and quick (4 weeks to pull it out, take to the machine shop, assemble, drop back in, and fire it up) rebuild.

You have to remember one thing, you usually have to sacrifice one for the other, power or gas mileage. Good luck.

Just took mine for a run to the Jersey shore. Mostly highway in overdrive 171 miles round trip, stop and go on LBI. 171 miles/7.4 gallons fuel. 89 iroc, zz-4 block otherwise all stock. 195stat, 5-30 Mobil1.

yea tpi 383's usually have that problem with hp..... they have a million pounds of tourque.... but mediocre hp...... cough-carb-cough

23mpg on my last tank, 95% highway driving. Kevin fixed my hot starting problem with some reprogramming, he rocks!

with the new 830 holley, sportsmanII heads and 4.33's in the pumpkin i get less than 10........alot less lmao

between 7 and 10mpg

Well,

I am going to go with a 357, just because it is cool to say I have a 357. Forged pistons, going to try for JE's, but have only found TRW for .040 over, Aluminum L98's ported and polished, super ram, Compucam 2032, speed Density setup, SLP dual cold air kit, 1.6 rr (for extra lift)... Get the tuning down right and I hope to be at 350hp and 25mpg...

Woohoo! Vegas here I come.

thanks for everyones help.

I get 20-22 mpg hiway. 14-15 mpg city (probably, it's bad).

Remember aerodynamics in my case (=barn).

I have a 350 w/ mods in the sig. doing 80mph for 1000miles I got 28mpg. in town when I"m playing is a different story now :-) about 8-10 :-/

Hey V8astro captain is that your band? Sounds like Korn, P.O.D, and sepultura got together and had a kid. Sounds pretty cool.

James

Hey Guys!
I'm still breaking in my new motor, but I want to know what you think I should be able to get for mileage. You can see what I've got in the sig. fairly straightforward 350 bored 30 over with a 6 speed and 3:73's and so far around town, getting on it from time to time I've gotten around 10 mpg or a little less....I'd like to be able to get 20+ mpg on the highway when all's said and done...do you think that's reasonable or not? Right now I've got a 600 cfm Holley on it, and I'm probably going to eventually be putting a 750 on, but anyway, let me know what you think about my expectations for mileage, any ideas or thoughts would be greatly appreicated!! Thanks so much!

-Paul

355, SLP .500 .500 cam, tfs heads, miniram, some other stuff...3.45 gears, im getting about 28mpg on the highway, and 21 mixed highway, city Gotta love 6th gear

5.2mpg in the city, never had it on the highway, can't keep my foot out of it either yet.

Well, updating mine...I ended up going fuel injected with a Holley Stealth Ram. Once I got it running right I made 295 RWHP on 87 octane and it gets 13-15 mpg around town and 22-24 mpg on the highway. I drove it to FL and back on the Hot Rod Power Tour this summer too! Sadly one of my RUSSELL steel braided brake hoses failed and I hit 2 vehicles, so the '84 won't be on the road again....but I have a '92 to swap all my parts into! Anyway....quite an impressive range of fuel "economy" going on in this post

-Paul

yea i get about 18 in the city.. winnipeg city.. more stops and goes than you can beleive, and about 26-28 on the highway