Impressed by 455 mpg.

jonstringer · 05-06-2008, 02:04 PM

Just a not-so-quick side note. I flew to Tallahassee, FLA to pick up my 1972 Cutlass S. I performed a fluid flush, inspection, set the timing, etc because it had been sitting a while... The engine, and transmission were both rebuilt less than 1k miles ago (documented) before I got my hands on it. It's a 455ci mated to a TH350 and a 2.73 open rear.

Here's what I have:
1. 455 w/ E Heads, forged crank, pistons, and rods. (not sure why the prior owner invested so much into the engine. Maybe he was building a racer.)
2. original Q-Jet also rebuilt
3. Cam unknown. No receipt, but a nice mild idle sound. Nothing radical.
4. Long tube headers by Hooker, mated to 2 1/4" Dual exhaust, 40 series Flow masters, w/ and H pipe.
5. Original snorkel Air Filter

I left the snorkel on, and forgot change the air filter, which was so caked with dirt it wasn't breathing at all. I drove my first tank of gas with this set up, (Avg speed 65 miles per hour) and achieved about 14.5mpg. I've never owned a GM Big Block so I figured this is how things work. I didn't know what to expect efficiency wise.

I stopped in a small town and checked the air filter, and saw how unsavory it was. I changed it out with a $23 open element 2" air filter from Autozone and tested it with my second tank of gas (avg. 65mph) and it was a much different story. I was averaging just over 17mpg, no joke. I monitored my fuel usage the entire way home, and it was consistently between 16.5 and 17.2mpg depending on my foot.

I was a little more than impressed by this fact. Also, the engine doesn't drop or burn any fluids whatsoever. Money well spent.

captainehh · 05-06-2008, 02:27 PM

It's nice to hear something positive amidst all the bad stuff in the news lately. Man, i wish all mods/fixes were that easy with such positive results!

jonstringer · 05-06-2008, 02:42 PM

No kidding. This puts a 455 Olds at the same highway efficiency as my Small Block Chevy engines. Unheard of.

Redog · 05-06-2008, 05:35 PM

That's very impressive for a 455. My 3.4 liter Alero gets around 20 MPG with a combo of city/highway driving.

Dying to know what the Delta's doing with the 350 in it. I'm guessing between 12 and 15 with city/highway driving, but with no odometer, I can't really do anything but guess. Speedo is now hooked up

68conv455 · 05-06-2008, 05:42 PM

Thats it! I'm scrapping my 250 cu.in. 6 cylinder for a 455. Rats! Ive already done that.

Oldsguy · 05-07-2008, 05:11 AM

2.73:1 gears and a quadrajet on the highway with the driver exercising some foot control.

87cutlas · 05-07-2008, 08:01 AM

i drive a 87 cutlass with a 307, no internal mods, rollercam engine, just put on a 600cfm edelbrock carb and scrapped the computer, minus the fact that the tranny won't kick down unless you manually down shift or slow down, i went from 7mpg to 17 to 20, inner city. i just have the 200m 3 speed tranny and some 2:73 rear gears

oh ya its still stock and it beats the mustang gt's with ease

88hurstolds · 05-07-2008, 10:40 AM

When I drove to the Olds nationals last year I calculated roughly 16-17 mpg on the highway with my C headed 455 as well, not too shabby for a bbo with a 3 speed trans and 3.08 gears. Of course it doesn't have a wild cam and it has stock intake and exhaust manifolds. I started to use the argument that my carb fed Olds was better than most SUV's when criticized about fuel efficiency. Of course street driving is a different story

It actually gets better gas milage than my stock 72 350 daily driver (11mpg street, 15 hwy) with 2.14 gears and a three speed trans.

Omicron · 05-08-2008, 06:13 AM

Quote:

Originally Posted by Oldsguy

2.73:1 gears and a quadrajet on the highway with the driver exercising some foot control.

Exactly right.

Gaz Hog · 05-08-2008, 08:32 PM

Mine is a '69 Delta 88 with a 455. I had a 2 bbl on it, but since changed the intake manifold, put HEI on her and a Quadra-Jet. So long as I stay out of the double barrel, I get around 14 or 15 (better than my 86 bronco). When I stomp, I probably get more like .14 or .15!!

Deltarocket · 05-11-2008, 06:03 AM

I'd be willing to bet, that it would get even better with a 4 speed overdrive.

rrielley · 05-11-2008, 07:58 AM

...but I'd never be able to keep my foot out of it and I'd be back down to 10-12 mpg

oldscsc · 05-12-2008, 03:39 PM

Those Quadrajets are great for mileage. Good economy until you romp on it

05-06-2008, 02:04 PM	#1 (permalink)
jonstringer Member Join Date: Feb 2008 Location: Austin, TX Posts: 31	Impressed by 455 mpg. Just a not-so-quick side note. I flew to Tallahassee, FLA to pick up my 1972 Cutlass S. I performed a fluid flush, inspection, set the timing, etc because it had been sitting a while... The engine, and transmission were both rebuilt less than 1k miles ago (documented) before I got my hands on it. It's a 455ci mated to a TH350 and a 2.73 open rear. Here's what I have: 1. 455 w/ E Heads, forged crank, pistons, and rods. (not sure why the prior owner invested so much into the engine. Maybe he was building a racer.) 2. original Q-Jet also rebuilt 3. Cam unknown. No receipt, but a nice mild idle sound. Nothing radical. 4. Long tube headers by Hooker, mated to 2 1/4" Dual exhaust, 40 series Flow masters, w/ and H pipe. 5. Original snorkel Air Filter I left the snorkel on, and forgot change the air filter, which was so caked with dirt it wasn't breathing at all. I drove my first tank of gas with this set up, (Avg speed 65 miles per hour) and achieved about 14.5mpg. I've never owned a GM Big Block so I figured this is how things work. I didn't know what to expect efficiency wise. I stopped in a small town and checked the air filter, and saw how unsavory it was. I changed it out with a $23 open element 2" air filter from Autozone and tested it with my second tank of gas (avg. 65mph) and it was a much different story. I was averaging just over 17mpg, no joke. I monitored my fuel usage the entire way home, and it was consistently between 16.5 and 17.2mpg depending on my foot. I was a little more than impressed by this fact. Also, the engine doesn't drop or burn any fluids whatsoever. Money well spent.

05-06-2008, 05:35 PM	#4 (permalink)
Redog Alero Chapter Secretary Join Date: Aug 2006 Location: Newtown, PA Posts: 776	That's very impressive for a 455. My 3.4 liter Alero gets around 20 MPG with a combo of city/highway driving. Dying to know what the Delta's doing with the 350 in it. I'm guessing between 12 and 15 with city/highway driving, but with no odometer, I can't really do anything but guess. Speedo is now hooked up __________________ Me 2000 Alero running 14's 1985 Delta 88 w/1968 350 rocket 2005 Nissan Altima (her's)

05-07-2008, 05:11 AM	#6 (permalink)
Oldsguy Administrator Join Date: May 2004 Location: Lees Summit MO Posts: 2,990	2.73:1 gears and a quadrajet on the highway with the driver exercising some foot control. __________________ Dan '46 2 door

05-07-2008, 10:40 AM	#8 (permalink)
88hurstolds Junior Member Join Date: Mar 2008 Posts: 8	When I drove to the Olds nationals last year I calculated roughly 16-17 mpg on the highway with my C headed 455 as well, not too shabby for a bbo with a 3 speed trans and 3.08 gears. Of course it doesn't have a wild cam and it has stock intake and exhaust manifolds. I started to use the argument that my carb fed Olds was better than most SUV's when criticized about fuel efficiency. Of course street driving is a different story It actually gets better gas milage than my stock 72 350 daily driver (11mpg street, 15 hwy) with 2.14 gears and a three speed trans. __________________ Mike 88 H/O - White/Red 455/400 88 H/O - Black/Gold 307/2004R 87 442 -1 of 300 Canadian Exports, Frame Off Resto 85 442- White/ Blue T-tops - Wanted 84 Calais - 15th ann. H/O Clone- Sand Drift Interior 350/350 8.5" 3.42 rear -Lightend with stock components: Heater box, removed A/C & ECM, Aluminum - Core Support, hood, bumpers, manifold, F body radiator, break drums. 72 C-10 - Parts Hauler

05-11-2008, 07:58 AM	#12 (permalink)
rrielley Member Join Date: Jan 2008 Location: London Posts: 56	...but I'd never be able to keep my foot out of it and I'd be back down to 10-12 mpg __________________ Ray '72 Supreme

05-06-2008, 02:27 PM	#2 (permalink)
captainehh Junior Member Join Date: Apr 2008 Posts: 5	It's nice to hear something positive amidst all the bad stuff in the news lately. Man, i wish all mods/fixes were that easy with such positive results!

05-06-2008, 02:42 PM	#3 (permalink)
jonstringer Member Join Date: Feb 2008 Location: Austin, TX Posts: 31	No kidding. This puts a 455 Olds at the same highway efficiency as my Small Block Chevy engines. Unheard of.

05-06-2008, 05:42 PM	#5 (permalink)
68conv455 Senior Member Join Date: Oct 2007 Posts: 111	Thats it! I'm scrapping my 250 cu.in. 6 cylinder for a 455. Rats! Ive already done that.

05-07-2008, 08:01 AM	#7 (permalink)
87cutlas stock so far Join Date: Jan 2008 Location: Omaha, NE Posts: 13	i drive a 87 cutlass with a 307, no internal mods, rollercam engine, just put on a 600cfm edelbrock carb and scrapped the computer, minus the fact that the tranny won't kick down unless you manually down shift or slow down, i went from 7mpg to 17 to 20, inner city. i just have the 200m 3 speed tranny and some 2:73 rear gears oh ya its still stock and it beats the mustang gt's with ease

05-08-2008, 08:32 PM	#10 (permalink)
Gaz Hog Junior Member Join Date: Oct 2007 Location: Harrisonburg, Virginia Posts: 17	Mine is a '69 Delta 88 with a 455. I had a 2 bbl on it, but since changed the intake manifold, put HEI on her and a Quadra-Jet. So long as I stay out of the double barrel, I get around 14 or 15 (better than my 86 bronco). When I stomp, I probably get more like .14 or .15!!

05-11-2008, 06:03 AM	#11 (permalink)
Deltarocket Member Join Date: Jan 2007 Posts: 46	I'd be willing to bet, that it would get even better with a 4 speed overdrive.

05-12-2008, 03:39 PM	#13 (permalink)
oldscsc Junior Member Join Date: May 2008 Location: Kansas Posts: 11	Those Quadrajets are great for mileage. Good economy until you romp on it __________________ '94 Cutlass Supreme Convertible (3.4 Mini-Hemi DOHC/204 c.i.d.) '99 Chevy Suburban (5.7 Vortec/350 c.i.d.) (Sold) '01 Chevy Silverado (4.8 Vortec/294 c.i.d.) '66 GMC Pickup (5.0/305 c.i.d. Big Block V6) http://www.cardomain.com/id/oldscsc 3.4 DOHC Info http://www.angelfire.com/ca2/34Performance/dohc.html

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