gas mileage expectations

[hyatt]

biggest mistake most people make with a street engine is too much cam and too large carb 600 cfm will cover about any streetable small block

[414banger]

as far as the carb goes i called holley and this is the carb they recomended the truck runs damn good just looking for ways to approve mpg's alittle lol but i guess with this size motor with no overdrive a high stall and a heavy right foot i really cant complain

[Rufton]

How did you tune the carburetor?

[414banger]

Thr carb is a 4160 holley non adjustable ready to run right out of the box
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[Rufton]

Originally Posted by 414banger

Thr carb is a 4160 holley non adjustable ready to run right out of the box
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If carb is tuned out of the box to match a modified engine then you a lottery lucky.

If I can tune a 1966 Stromberg, 1967 Autolite, and 1998 Edelbrock I'm guessing a 4160 Holley can be tuned.

[Rich 5150 69]

He can jet it down 2-size jets on both primary and change out the metering plate on the secondarys....

[theastronaut]

Originally Posted by Rufton

I installed a wideband air/fuel O2 gauge.
My analog AEM UEGO cost about $200 and allows me to monitor the carb tune all the time. This is important to control mpg and to verify sufficient fuel to prevent engine damage during those WOT splurges.

I swapped an aggressive cam (similar to comp extreme energy ) for a lower rpm torque monster cam (lower lift/dur) and the hwy mileage remained the same. Can't judge city mpg because function of foot weight

I would verify your intake is efficient at the rpms you cruise if $ a concern. A tall intake may be power efficient at 6500rpm but gas inefficient at hwy cruise rpm. A shorter intake can improve low rpm power and mpg at expense of high rpm power.

Rear gears can make significant mpg improvement if you keep rpms in the efficient range. Some have installed overdrive and lost mpg because engine not tuned for low rpm operation.

^^^ THIS!!! ^^^

I have a wideband gauge in my '64 VW bug too, and it's great for tuning for both cruising efficiency and WOT performance.

I went from 24 mpg hwy with a stock 1600cc with a stock single barrel carb, to a best of 36.25 mpg hwy with dual-two barrels on individual runner intakes, ratio rockers, and a header/muffler. It picked up over a second in the 1/8 mile and 12 mpg! Had I used a distributor that added in vacuum advance while cruising, the mpg would have been higher than that! It's not always about what performance parts you have, it's how well tuned it is and how well the combination of parts work together.

Most people just slap a carb on and run it as-is with almost no tuning. You need to optimize the air/fuel ratio AND timing for both cruising and WOT performance. To do that you need a distributor with vacuum advance and an AFR gauge to see how your jetting is.

I'll have a 5.3 LS engine in my '66 with four Weber 51mm two-barrels on an individual runner intake, a T56 six speed, and 4.56 or 4.88 gears. If it doesn't get atleast 15 city and 20 highway mileage I'll sell it... If my sister's Trailblazer SS can get 16/20 mpg with a 6.0 then I don't see why my much lighter C10 with more overdrive can't get atleast that much.

[jayoldschool]

I'll have a 5.3 LS engine in my '66 with four Weber 51mm two-barrels on an individual runner intake, a T56 six speed, and 4.56 or 4.88 gears. If it doesn't get atleast 15 city and 20 highway mileage I'll sell it... If my sister's Trailblazer SS can get 16/20 mpg with a 6.0 then I don't see why my much lighter C10 with more overdrive can't get atleast that much.

You'll get 20mpg with that combo, no problem. I get over 25 with my modded LT1/T56/4.10 4200lb 95 Impala SS.

[414banger]

20 miles per lmao i didnt get 20 miles per gallon in my 98 silverado with 5.7 in it driving highways all the time and another thing im cruising at 3000 on the highway there is no way im going to get 20 lol again but thanks for the input guys
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[theastronaut]

Originally Posted by jayoldschool

You'll get 20mpg with that combo, no problem. I get over 25 with my modded LT1/T56/4.10 4200lb 95 Impala SS.

Impala is much more aerodynamic though! A buddy of mine had a '97 Camaro SS that got 28 on the highway, those are even more slippery. The truck is like driving a brick lol. I'm thinking about building a full length belly pan to help with that while not looking like one of those goofy hyper-milers!

[jayoldschool]

I lol'd...

yes, the SS is slippery. Very low CD for a big car. I still think your light C10 will be ok.

[joedoh]

I need to do something different I think, because I dont daily drive a v8 truck/camaro/caprice, my daily is a 1.8l 5spd and it gets 26.2 mpg 60% highway. I calculate my mpg by filling up to the click, resetting odo, and driving till empty when I fill up to the click, then divide the odo miles by the gallons needed to fill up. I could stretch that maybe another 1-2mpg if I drove like a hypermiler.

Sounds like I either left a lot of car on the table or there is more baloney here than a deli.

[jayoldschool]

Small displacement engines spin fast in top gear, and have low torque. FWIW, my wife's 1.8T VW gets 31mpg mixed. My LT1/T56/4.10 car is only turning 2000rpm at 65mph.

[skysoldier173rd]

stock 350 with 700r4, quadrajet, headers. get around 25 MPG and cruises about 2 grand at 70MPH on the highway. Unsure of what rear, it came with the 305 v-6 and granny 4 spd.

[luvbowties]

Originally Posted by joedoh

I need to do something different I think, because I dont daily drive a v8 truck/camaro/caprice, my daily is a 1.8l 5spd and it gets 26.2 mpg 60% highway. I calculate my mpg by filling up to the click, resetting odo, and driving till empty when I fill up to the click, then divide the odo miles by the gallons needed to fill up. I could stretch that maybe another 1-2mpg if I drove like a hypermiler.

Sounds like I either left a lot of car on the table or there is more baloney here than a deli.

I assume you're comparing your car to jayoldschool's Impala. If so, you need to remember that LT1 w/its od and genuine port injection is likely one of the most fuel-efficient engine-tranny-combos Chev has produced.

I think it's ridiculous to fathom that the Vettes w/that engine and 6-speed may have to pay a gas-guzzler tax: on a 1000-mile round trip to Fla., mostly I'state, those cars could deliver astonishing mpg--I've heard from several that would do 30 on that trip (I'll add that it might have been on the trip down--same on trip back up--less while cruising the Fla. blvds. while down there!!!).

I just sold an '87 S-10 Blazer with a '95 LT1 with 4L60E that would do well into the 20's (23+) on I'state trips. Never tried it, but I'd bet(be it just a little!) my '66 C10 with a '96 carb'd Vortec 5.7, 3.73, and 700R4 wouldn't do much over half that!

That said, your 1.8l and 5-speed probably did not cost new anywhere close to that '95 Impala SS OR those LT1-'Vettes--maybe not what the builder of that '87 S10 Blazer spent either!

Enjoy that 26.2 mpg--and the discounted 'new price'!
sam

[joedoh]

If I go to fueleconomy.gov, my mpg is right in line with the combined average, I mean +0.6mpg. some of these stated mpgs are 6-10mpg above. I dont know how mine can be so exactly right and the others can be so high, but I dont want to argue about it either.

the corvettes are on there and list a highway mpg of 26, so I could see a guy doing better in a pure highway situation.

[luvbowties]

Originally Posted by skysoldier173rd

stock 350 with 700r4, quadrajet, headers. get around 25 MPG and cruises about 2 grand at 70MPH on the highway. Unsure of what rear, it came with the 305 v-6 and granny 4 spd.

As I heard someone ask earlier, "Have you welded the hood shut yet?" I'd be reluctant to even change spark plugs. Reckon you are that deserving--or just that lucky?

All joking aside, that is fantastic mileage; probably the best I've heard about in our old trucks. Even Clyde65's 4.8L/4L60E doesn't come close to yours!

Sam

[skysoldier173rd]

actually been quite surprised by the rear in this old truck being as high as it is and the 700r4 with OD/Locking Converter make it a nice highway ride. I had to extend the upshift as the normal shift change made it bog a little.

[Rich 5150 69]

Stock vortec 350/quad fed, 350/3.73 gears 18 mpg at 60....not to bad.

[Trsmotrhed]

I just installed an LT1/4L60E in my 63. My truck had 3.08 gears from the 72 I got the rear from. At 80mph my rpm is 2000rpm. Just tried it out last night on interstate.I hope to get in the upper teens and would be happy to get into the 20's. My 66 C10 had a 383 stroker I had, but sold didn't pass many gas stations, but thats how I built the engine, nasty cam n all the go fast parts and stall converter. Sure was fast though. I always said the next truck I built would have fuel injection so i could travel to car shows. I love it so far. In my experience most 350 's in trucks with 350 tranny are lucky to get 10-12 mpg
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[Rich 5150 69]

I`m looking to either run a NP-440 or 200r4...slightly built...

[theastronaut]

Originally Posted by jayoldschool

Small displacement engines spin fast in top gear, and have low torque. FWIW, my wife's 1.8T VW gets 31mpg mixed. My LT1/T56/4.10 car is only turning 2000rpm at 65mph.

Not necessarily- my 1679cc vw engine has a flat torque peak from 2300-3500 rpm. It could benefit from a little more overdrive.
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[brokenspoke]

18 MPG in my 65.....new crate 350, T-5 speed, 3.73 gears, 600 edlebrock, dual exhaust, Hei

[414banger]

thanks for all the replies i think all i need is another gear lol but until i can have a good 7oor4 built im going to keep sucking gas and hauling ass with my 400 turbo i better start saving now for my 2 hr trip to columbus in july for the ppg nationals

[Rufton]

Originally Posted by 414banger

thanks for all the replies i think all i need is another gear lol but until i can have a good 7oor4 built im going to keep sucking gas and hauling ass with my 400 turbo i better start saving now for my 2 hr trip to columbus in july for the ppg nationals

Sounds fun.
Good luck and keep er between the ditches.