Hello guys since the weather is finally getting better here in Ohio I am finally going to be able to start driving my truck again and work a few kinks out but anyways I am curious as what do you guys who are running 1st gen small block chevy's that are mild and daily driver type setup what do you guys get fuel mileage wise on your build?

What I mean is heads can be whatever but for camshaft size 230@ 50 duration and smaller and can be either roller or flat tappet and carb size does not matter along with compression and can even be stock. I am just trying to see how mine does compared to other builds similar like mine.

My engine is in a 1996 s10 with a 350 turbo transmission and 3.42 rear end gears. My engine specs are 350,9.1 CR, 275/280 208/221 @50 474/510 zz4 hydraulic roller.

World sportsman 2's gasket matched and bowl blended with competition valve job. Holley 600 1850 VS carburetor with edelbrock performer eps dual plane with aftermarket hei high output ignition setup.

I have not been able to really calculate my mileage yet but so far it seems maybe I am getting 13 to 14 mpg at the very most but that is probably being hope full.
My engine should be in the 350/375 hp and close to 400 pounds of torque at the flywheel. Hope you guys will contribute.
Thanks Eric

I'd be happy with that, that's usually what my 96 305 3/4ton truck gets with central sequential fuel injection and 4l60e in city. I get about 18mpg highway on a good day.

 

Tell us about the distributor - initial mechanical timing, total mechanical timing, and vacuum advance amount added. This can make or break fuel mileage.

What have you done as far as carb tuning??

 

I have my timing setup with 12-14 initial and 32-34 total mechanical by 3000 to 3500 rpm and I have around 14-15 degrees of vacuum advance and its hooked up to full manifold so at idle is around 26 to 28 degrees at a 800 rpm idle in park.

I have not really not had the time to go over some things on my carb as I had in another post but since the weather has warmed up some my carb has not given me any stumbling like I posted before.

Everything is tuned very well wise as best as I can do by looking at plugs and how the truck runs. I don't have a afr gauge at this point and time. Cruising the thing runs very smooth and wide open it runs very good as well with no issues at present time but I really don't ever do anything more then 3/4 throttle when having to pass or anything like that.

The other week I burned up a 1/4 of a tank of gas from an 18 gallon tank but doing several wide open shots driving and getting on it up to about 90 is what made it do that Just wanted to take it out and give it a nice run. Driving to work I have about 4 miles through town and 1 mile highway and is a total of 8 miles town and 2 miles everyday round trip and after about 5 days I have used about 7 to 9 gallons of fuel give or take some depending on traffic situations etc.

I have calculated better mileage then this before but I was just curious what you guys get as to see if I am not expecting too much from mine. I feel like I am not getting very good but maybe like I said I am not being real but I don't really know what is about average for a 350 performance wise. I have read some guys making over 16 mpg with a setup similar like mine.

Carb is jetted 67 primary and 72 secondary at the moment and seems to be running fine this week as compared to last week when it was much colder out and that might of been what was causing my stumbling during real low rpm cruising under 1500 rpm in drive.

Eric

 

With a carb I would consider 22 mpg very good, 17-19 mpg a target to shoot for, and 14 needs work in your case.

A Quarajet, or even the 4165-4175 Holley spreadbore replacement would be a better bet than the 600 VS squarebore due to their smaller primary throttle bores.

With the 600 Vacuum you will need to reduce the size of the main jet, then enlarge the size of the power valve channel restrictions to get back to correct WOT A/F ratios if you are going to try to improve mileage with this carb.

 

I don't want to get rid of my current carb I already got as I have a lot of time invested in it and I am not trying to get 20 mpg which out side of fuel injection and a bone stock motor I won't ever see that with mine. I was just wondering what others get for mileage wise compared to what I have that's all. Just trying to get an idea on what I should be looking for mpg wise compared to others. My Father has the same carb on a stock 302 ford and he can get almost 19 mpg highway with a four speed in a ford f150 mid 90's model and a heavy foot of all things lol but his is a stock motor. Just trying to get an idea on what mpg highway and in town I should be looking at here and to be able to see if I am in the right area on what mine would normally do for what my engine setup is.
Eric

 

9 all stop and go, most of it never over 45 mph.

SBC bored 60 over, performance cam (dont know so cant tell you)
Carburated
If I could keep my foot out of it and keep the rpms below 4500 I would probably get better mpg. But wheres the fun in that.

http://www.youtube.com/watch?feature=player_profilepage&v=GnDrDs225EI

 

I have an 89 S15 at 2800 pounds with a Franken mouse 350 built on a 880 Vortec block with LT1 heads modifed to conventional cooling, MAP sensed batch fire injection on a modified LT1 4 barrel conversion intake, flat top pistons, .025 deck .040 gasket, 55cc chambers the SCR is 10.4 the DCR with the LT4 cam and 1.6 rockers is 10.4 and the DCR is 8.5., ignition is 15 degrees base and 21 variable computer managed. Tranny is B&M 4L60E, rear is 3.08 with posi. Exhaust is Sanderson shorties into 36 inch collectors with H pipe, dual cats, dual Thrush galss packs, vehicle is SMOG compliant at the tail pipe but not a legal configuration. Tires are 245-55x16 Goodyears. Chassis has 315,730 miles, Frankenmouse has 183 thousand and some miles and it is still a very strong runner.

Daily commute which is 5 miles in town and 25 miles rush hour freeway it gets 18 to 22 depending on the weather, how much the stop and go is and how heavy my foot gets to make up time when I can. This is close to what the truck got with the original Iron Duke 4 with a 5 speed.

Bogie

 

My 350 gets probably around 12-15 mpg. Its in a 78 firebird, th350 trans, stock highway gears. Carb is edelbrock 600, 9.5 compression, mildly ported heads, holley contender intake, cant remember cam specs (1500-5500 rpm range).

 

I would swear my old 72 C-10 with a 350/350 (qjet IIRC) and 3.73 rear with 31x1050s made 14mpg in town.

14mpg is what I calculated but it seemed to me like a high figure for that truck.

 

i'm kinda out of this because of you wanting mild engine input, but my 383 only gets around 8 mpg but that's with a double pumper and about a 1000 rpm idle.

in some of my previous motors though, with a vac sec carb and mild set up on a 383 i was getting about 12-14mpg

 

Don't forget that Ethanol laced fuels will net you lower MPG than reguler non crap gas.

 

72 C10 383, EPS dual plane, eddy 600 1405 stock jets/rods, vortec heads, 9.5 scr, 221 dur @ 50, 1-5/8 headers, dynomax turbos, 2-1/4 all the way back, 700R4, 3:73's, 375HP, 3900 lbs 16 city, 22 highway. (summer only)

06 Nissan Frontier crew cab 4x4, 4.0L, all stock, 265HP, 4400lbs, 14 city, 21 highway. (winter at -25 Deg C,,,just got this pig)

All light foot easy going driving., yeah I can't wait for spring

 

gas

My 350 in a 1989 1/2 ton 2wd Chev reg cab long box and stock rearend got about 10 mpg. The motor had an Edelbrock performer plus cam 204 in. 214 ex dur@.050 and .420 in. .442 ex lift. An edelbrock 600 carb. The truck ran great and I leaned out the carb to improve milege but it got the same. I just drove the hell out of it and sold it to a person who wanted the power and did not care about the gas.The pistons were old pop up 11 to 1,s and the heads were smog open chambered that I cleaned up with the rotary file .

 

Were not sure as we`ve never checked on my friends `84 cutlass. However, it has RHS Vortec heads, .215 duration roller cam, flat top pistons, .045 quench distance, headers, edelbrock performer intake, Quadrajet carb. HEI with pertronic internals. Dual exhaust with flow masters. TH350 with 2400 Stall, 3.42 posi rear. His work place is 20 miles there, 20 miles back. He can fill up on sunday night, and when he gets off friday morning by the time he gets home he still has half a tank. His wife has a 2001 Expedition, his cutlass gets better mileage than it does.

 

Thank you guys very much for your input. From what it seems I should get at least 10 mpg or a little more looking at some other combos. I won't know till I get to steady driving and check after a few weeks.

I am getting a speedometer to put in and keep track of my mileage etc. That some really nice engine combos posted. It seems like as of now the fuel mileage is not as good as it should be compared to other's above.

Custom10 and double vision's friends cutlass are very close to what mine is minus a few things and vehicle weight along with carburetor.

I used to have a edelbrock 600 carb on my engine when I first put it together and the mileage before I had did a cam swap and had to tear engine down cause of valve seal issues but I did not really make much difference between my holley 600 and the edelbrock.

My drive starts with a 5 minute warm up in the morning before driving and then I have about 4 miles town and 1 mile highway which makes 10 miles round trip with 8 being town and 2 highway and if I fill up my 18 gallon tank in my truck and without getting on it any by the end of the week after 6 days I used to use around half a tank or just a little more say 1/16th give or take. If I take 9 gallons of fuel divide from 60 miles it calculates to only 6.6 miles per gallon which seems awfully low compared to others on here.

That was with my old crane 222/230 @ 50 roller cam but I have switched to the gmzz4 roller cam for better street manners. Everything on my engine is only a year old and everything carburetor,ignition,charging system,vacuum hookups etc has been inspected checked and verified to all be working and adjusted correctly wise. thanks guys for you specs gives me ideas.
Eric

 

Eric, cut down that warm-up by 3 minutes. I know it's winter and it's cold but going no where while an engine idle's hurts mpg, especially in a 'rich' setting such as warm up (choke on).

As has been stated, 10% ethanol hurts. Google 'non ethanol gas stations', there should be a website that will let you search in your area for 100% gas dealers. Maybe you can luck out and find one.

On top of that, winter fuel has a lower btu (energy content) than a summer blend.

I mix 2 ounces of Marvel Mystery Oil + 2 ounces of TCW-3 (marine two stroke oil) for every 11 gallons of gas. It's helped my mpg .5 - 1 mpg in my '03 Dodge. Sure, it's a computer/ EFI but maybe it could help with a carb also. Haven't tried it yet.

What oil are you using? A 5w-30 could help cold starts and energy use (make sure you add some type of Z & P additive, unless you are running RedLine or other botique HD oil). Along those lines, your commute is relatively short, make sure to keep the oil change interval 5K or less. Fuel dilution from long idling and short trips wreaks havoc on the base number of your oil.

 

Thank you guys very much for your input. From what it seems I should get at least 10 mpg or a little more looking at some other combos. I won't know till I get to steady driving and check after a few weeks.

I am getting a speedometer to put in and keep track of my mileage etc. That some really nice engine combos posted. It seems like as of now the fuel mileage is not as good as it should be compared to other's above.

Custom10 and double vision's friends cutlass are very close to what mine is minus a few things and vehicle weight along with carburetor.

I used to have a edelbrock 600 carb on my engine when I first put it together and the mileage before I had did a cam swap and had to tear engine down cause of valve seal issues but I did not really make much difference between my holley 600 and the edelbrock.

My drive starts with a 5 minute warm up in the morning before driving and then I have about 4 miles town and 1 mile highway which makes 10 miles round trip with 8 being town and 2 highway and if I fill up my 18 gallon tank in my truck and without getting on it any by the end of the week after 6 days I used to use around half a tank or just a little more say 1/16th give or take. If I take 9 gallons of fuel divide from 60 miles it calculates to only 6.6 miles per gallon which seems awfully low compared to others on here.

That was with my old crane 222/230 @ 50 roller cam but I have switched to the gmzz4 roller cam for better street manners. Everything on my engine is only a year old and everything carburetor,ignition,charging system,vacuum hookups etc has been inspected checked and verified to all be working and adjusted correctly wise. thanks guys for you specs gives me ideas.
Eric

A long time ago I had a 78, 1/2 ton, Scottsdale, standard cab, short bed with a 350 and a 4 speed with a final gear of 3.73. It got 9.5 mpg in the city, in the country, up hill, down hill, against the wind, with the wind. I was never happy with the engine power so I suped it up with better heads, more cam, big Holley, headers and duals. It continued to give 9.5 and while better it still had less than stellar power. I pulled the 350 and put in a 454, a lot better power, still 9.5 mpg.

Bogie

 

My thoughts on the combo of parts I used on my friends build was simple as for street engines I always focus on the following things:
Maximize combustion efficientcy.
Reduce all the friction as possible.
Use a Roller cam with mild specs for excellant torque and street manners.
Use a Rochester Quadrajet, it`s small primary`s make for excellant low end torque and throttle response so sensitive you swear it`s fuel injected.
Don`t Skimp on the tune up. Use the best pieces you can get. In his case, the coil and module are pertronix flame thrower pieces. The cap and rotor are brass terminaled, and the spark plug wires are moroso 875 Ohm spiral core wires that are routed correctly and kept away from each other.
Don`t skimp on the tune. Make sure the carb and ignition timing on are on the money.
Fill the rear diff with Royal Purple Synthetic lube.
Pack the wheel bearings with Synthetic grease.
Use mineral oil for engine break in. Then switch to synthetic oil afterwards.
The use of synthetic oils cuts rolling resistance.
We used a K&N air filter in a stock air cleaner housing plumbed to a direct cold fresh air source. Engines make more power with cooler fresh air than Underhood stale air.
As for combustion efficientcy, I shot for a .045 distance and came out on the money, the compression ratio is 10.3:1. We used flat top pistons with 2 valve reliefs. The tight quench used with the fast burn chambers of the Vortec heads and a Quadrajet carb was a great idea, as the better combustion characteristics reduced the amount of initial and total spark timing which is a clear indication of a better burn and the small primary`s of the Quadrajet keeps velocity high for good throttle response. We thought about using a 700R4 tranny, as the use of Overdrive would have been beneficial, but we already had the TH350 so we used it. One thing I believe in on street engine is to focus on the torque output. And on my friends car as a example, it takes very little pedal to make it get up to 55 and it gets there quickly. The combined parts combo is what makes it this way, the less pedal used the less fuel used.
The next step is cruise RPM, the lower the RPM the better. However, with a carb you really can`t have a cruise speed lower than 1900 RPM. My 4.3 V6 in my truck has a 5 speed. in OD it cruises at 55 doing 1700 RPM, and it doesn`t lug down on hills which goes to show injection works far better for lower cruise RPM. Overall, I have several ways I look at it and I design the combo and match the parts to get a balance of good power and mileage.
There`s more I could say but this post is already a book. If you want I`d tell you about the combo I did for my own Cutlass, had the machinist not screwed the bores up, it would have netted over 20 MPG with a 700R4 tranny and 350 cubic inches.

 

Thanks guys for all your posts much appreciated. It seems to me something is not right with my combo as my entire engine is roller with full roller rockers and roller cam. I have not shorted or anything. I got a good HEI distributor with really good plug wires that are way better then stock type wires and are low resistance type and carburetor is tuned really well as I just took out one of my plugs and the porcelain area is a nice tan color.

First time for that. As far as goes I don't use 90/10 blend I only go to stations that are 100 percent gas no ethanol. I have done everything I can with my engine and it seems I just can't get rid of some dam misfire that is a mild misfire but you can hear it while idling and even bringing the rpm's up to around 2000 in park you can still hear it.

O well I am sure that can have a part in my lower then expected fuel mileage but this problem has plagued me for over a year now. Part of it was valve seals letting oil past but that has all been taken care of as I had new and better seals and new guides put in my heads.

I readjusted my idle mixture screws on carb yesterday for best vacuum and that was hard to do cause of the stupid misfire vacuum would keep dropping here and there and not stay steady. When I could get it to be steady I got my mixture screws adjusted for highest vacuum and now have 20 inches when it does not misfire. O well back to the drawing board. About ready to get rid of the dam thing with so much money put into it along with time and my Father who has built hundreds of hotrods and engines over the years can't even figure out why. Take care guys have fun with your nice rides with fuel getting even closer to 4 bucks a gallon this summer is not looking to fun.
Eric

 

I should convert to US gallon from our Imperial gallon,,,

4.6 liters in imp gal, 3.8 liters in us gallon

3.8/4.6 = .82

.82 X 16 = 13.1 miles per US gallon city for my C10, 18.0 highway

 

1970 C30 dually dump truck,6000lbs, 4.10 rear 4spd dead tired 307 with headers H pipe, turbo muffs,HEI, 2bbl, and new timing chain advanced. 11.5 on country roads.

 

8-10 i let it eat

 

Man I wish I could get like some of you others on here gets. I would be happy with 13/14mpg and I feel I should be making around that. Just because I had my world 2 heads bowl blended does not mean it should have taken away half of my fuel mileage and putting the zz4 roller cam which is a mild cam. It might have something to do with some misfiring I am starting to have again but I don't know for sure. Going to take to a shop and have a oscilloscope and see if I can really figure out what is causing it. Anyways thanks guys for you nice comments appreciated it.
Eric