Most MPG - The 1947 - Present Chevrolet & GMC Truck Message Board Network

davidh · 02-24-2005, 01:07 AM

I'm getting ready to swap out my 292 in for a 305 in my 67 C10. The 305 is out of a 80's camaro that was supposed to have been rebuilt. Which carb would be the best for MPG? I know the theory of 4bbl is that if you just put around in it the primaries are smaller than those on a 2bbl so you should get better mpg. But I've known some farmers who switched out to little 2bbls and claim they getter better mpg. I also have a 80's HO. aluminum intake. I think off a 305. So, I could use this and get a fresh quadrajet. I will plan on using an HEI of course too. I'd love to get 14-16mpg if at all possible. gas is going to be damn high this summer.

CHEVY & GMC FOREVER · 02-24-2005, 01:21 AM

Why change the 292 those d#$% motors will run seemingly forever.

TP from Cntl PA · 02-24-2005, 02:37 AM

I'd never swap a 292 for a V-8..............But I use a truck for work and I love an I-6.

I am putting in a Diesel before gas is $3

I've got a gas truck for winter when diesel is higher

86SILVERADO · 02-24-2005, 02:53 AM

I would also say that you are up for a potential dissapointment with the 305 over the 292. You will probably have about half the torque of the 292 with the 305 and in an old heavy truck you will know it.

davidh · 02-24-2005, 03:22 AM

Here's the deal. I have the 305 in a running car I got for $80. The 292 has 196K on it and it is tired. I've tuned it up. points plug, cap, wires had a carb rebuilt, changed out the leaky intake/ehaust and while it does run better it still is not what I'd like it to be. I've looked into possibly rebuilding a 292 but they cost double what a 350 would be to rebuild. I'd have to see one rebuilt and running good before I'd dish out the money. Plus everyone says the 292 uses as much gas a V8 anyway.

Boy you guys would really gripe if you heard I was thinking of building a little 283. I have one in my 63 belair and I really like it.

CHEVY & GMC FOREVER · 02-24-2005, 03:23 AM

**VetteVet** · 02-24-2005, 03:47 AM

Here's more than you ever wanted to know about the 305

http://www.goingfaster.com/spo/praisetbi.html

http://www.goingfaster.com/spo/mods.html

Vettevet

68C15 · 02-24-2005, 04:18 AM

I also agree with the 292 vs. 305 debate.
the 305 will work harder therefor reducing the MPG below that of the 292.
I have a Cadillac 472 which when complete expect to get about 18 MPG.
fuel mileage comes from the engine operating in the peak of the torque curve. it comes down to a measurement called volumetric efficiency.
I used to have a BUILT 355 in a 80K20. it got between 16 & 18MPG @ 3100 RPM. (that was at about 1/2 inch of gas pedal)

68w/sbc406 · 02-24-2005, 04:20 AM

if it was a 305 V6 i would disagree with these guys, its cool to be unique and you still have a butt load of torque

bagged91 · 02-24-2005, 04:30 AM

Holley used to have a small 4 barrel carb called an "Econo-Master". I don't know if you can still get a new one but I would try one of them before I tried a Quadrajet. They have small primary's & secondary's.

shortymac83 · 02-24-2005, 04:33 AM

just get a stock 750 cfm quadrajet off of any GM car that isn't on the computer, and be happy. with my 307, on the computer, I see 26 mpg with OD and 2.73's. Buddy of mine had a 307 in a 1973 omega (olds 307) with a quadrajet, headers and straight pipes, a TH350 and 3.08 peg legger in the back. He saw a best of 28 mpg on the highway, and averaged 15-18 mpg.

draino76 · 02-25-2005, 12:24 AM

I ran a 305 in my 70 for a few years, it had fair power and got around 17mpg. I ran headers, and an edelbrock 600 4bbl carb. It was no racer, but it was never shown up by a 6 cylinder, and it had pulled a trailer a few times with no problems.

02-24-2005, 01:07 AM	#1
davidh Senior Member Join Date: Feb 2004 Location: Ponca city now kingfisher Oklahoma Posts: 1,220	Most MPG I'm getting ready to swap out my 292 in for a 305 in my 67 C10. The 305 is out of a 80's camaro that was supposed to have been rebuilt. Which carb would be the best for MPG? I know the theory of 4bbl is that if you just put around in it the primaries are smaller than those on a 2bbl so you should get better mpg. But I've known some farmers who switched out to little 2bbls and claim they getter better mpg. I also have a 80's HO. aluminum intake. I think off a 305. So, I could use this and get a fresh quadrajet. I will plan on using an HEI of course too. I'd love to get 14-16mpg if at all possible. gas is going to be damn high this summer.

02-24-2005, 01:21 AM	#2
CHEVY & GMC FOREVER Registered User Join Date: Nov 2004 Location: New Lenox,IL Posts: 306	Why change the 292 those d#$% motors will run seemingly forever. __________________ 1985 Chevrolet C-30 454 1-TON Dooley 1969 CHEVROLET CST-10 PICK-UP Good memories 1999 Chevrolet Z71 Ext. cab 5.7L Good Memories With a quart of oil, and a gallon of gas, she won't let no other car pass!!!. & FOREVER

02-24-2005, 02:37 AM	#3
TP from Cntl PA Registered User Join Date: Apr 2003 Location: Central PA....In the Berg of Nisbet Posts: 790	I'd never swap a 292 for a V-8..............But I use a truck for work and I love an I-6. I am putting in a Diesel before gas is $3 I've got a gas truck for winter when diesel is higher __________________ '72 K-20 EFI'ed 250 Inline/4spd stake body, Farm Truck '71 C-20 Cummins Diesel Powered, In storage thanks to $5.00 diesel! '69 3500 GMC 305V-6/4spd, Still under reconstruction.......... Inlines Rule! 6 soldiers standing is better than 8 laying down!!!!!!!!

02-24-2005, 02:53 AM	#4
86SILVERADO Registered User Join Date: Dec 2002 Location: Hills of Western Mass Posts: 626	I would also say that you are up for a potential dissapointment with the 305 over the 292. You will probably have about half the torque of the 292 with the 305 and in an old heavy truck you will know it. __________________ 86 Silverado C10 back to 305 power! 67 C30 Dually Dump, with 350 transplant, Rockhauler 05 Duramax 3500 "If at first you don't succeed, try a bigger hammer" Member of the 1-Ton club!

02-24-2005, 03:22 AM	#5
davidh Senior Member Join Date: Feb 2004 Location: Ponca city now kingfisher Oklahoma Posts: 1,220	More Here's the deal. I have the 305 in a running car I got for $80. The 292 has 196K on it and it is tired. I've tuned it up. points plug, cap, wires had a carb rebuilt, changed out the leaky intake/ehaust and while it does run better it still is not what I'd like it to be. I've looked into possibly rebuilding a 292 but they cost double what a 350 would be to rebuild. I'd have to see one rebuilt and running good before I'd dish out the money. Plus everyone says the 292 uses as much gas a V8 anyway. Boy you guys would really gripe if you heard I was thinking of building a little 283. I have one in my 63 belair and I really like it.

02-24-2005, 03:23 AM	#6
CHEVY & GMC FOREVER Registered User Join Date: Nov 2004 Location: New Lenox,IL Posts: 306	__________________ 1985 Chevrolet C-30 454 1-TON Dooley 1969 CHEVROLET CST-10 PICK-UP Good memories 1999 Chevrolet Z71 Ext. cab 5.7L Good Memories With a quart of oil, and a gallon of gas, she won't let no other car pass!!!. & FOREVER

02-24-2005, 03:47 AM	#7
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,718	305 vs 292 Here's more than you ever wanted to know about the 305 http://www.goingfaster.com/spo/praisetbi.html http://www.goingfaster.com/spo/mods.html Vettevet __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

02-24-2005, 04:18 AM	#8
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	I also agree with the 292 vs. 305 debate. the 305 will work harder therefor reducing the MPG below that of the 292. I have a Cadillac 472 which when complete expect to get about 18 MPG. fuel mileage comes from the engine operating in the peak of the torque curve. it comes down to a measurement called volumetric efficiency. I used to have a BUILT 355 in a 80K20. it got between 16 & 18MPG @ 3100 RPM. (that was at about 1/2 inch of gas pedal) __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

02-24-2005, 04:20 AM	#9
68w/sbc406 Got Light Emitting Diode? Join Date: Apr 2004 Location: Newberg, OR Posts: 2,485	if it was a 305 V6 i would disagree with these guys, its cool to be unique and you still have a butt load of torque __________________ 1968 1/2 ton 2wd lwb 6 lug disc and bags up front. Next c notch and rear bags '02 Chevy Silverado LT ext cab short bed 2WD 5/7 drop on 22's(the family car) 1993 Cherokee work ride/weekend wheeler

02-24-2005, 04:30 AM	#10
bagged91 Out draggin' Join Date: Jan 2004 Location: Pitman,NJ Posts: 1,574	Holley used to have a small 4 barrel carb called an "Econo-Master". I don't know if you can still get a new one but I would try one of them before I tried a Quadrajet. They have small primary's & secondary's. __________________ 91 GMC Xcab LB-Bags/bd/caddy clip SOLD 72 C10 Cheyenne Super LWB SOLD 92 GMC K1500 Burb 72 C10 Burb (ex. Cheesewagon)SOLD 72 C20 Burb parts truck 71 C10 Burb "project"

02-24-2005, 04:33 AM	#11
shortymac83 hmm... Join Date: Jan 2004 Location: Culver, Indiana Posts: 1,631	just get a stock 750 cfm quadrajet off of any GM car that isn't on the computer, and be happy. with my 307, on the computer, I see 26 mpg with OD and 2.73's. Buddy of mine had a 307 in a 1973 omega (olds 307) with a quadrajet, headers and straight pipes, a TH350 and 3.08 peg legger in the back. He saw a best of 28 mpg on the highway, and averaged 15-18 mpg. __________________ 1983 Oldsmobile Delta 88 1967 Chevy C-10 stripper www.fcrperformance.com - wanna go...faster? talk to FCR.

02-25-2005, 12:24 AM	#12
draino76 FUJIMO Join Date: Dec 2004 Location: South Dakota Posts: 127	I ran a 305 in my 70 for a few years, it had fair power and got around 17mpg. I ran headers, and an edelbrock 600 4bbl carb. It was no racer, but it was never shown up by a 6 cylinder, and it had pulled a trailer a few times with no problems. __________________ IF IT DON'T GO--CHROME IT!! I dont mind confusion, I create it!

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