427 Crew cab mpg question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DustyNova · 10-23-2015, 02:03 AM

What do you guys usually get for 427/454s in your crew cabs?

BLE 'BURBAN · 10-23-2015, 03:09 AM

87 cc dually,454/TH400 RWD running stock size 215/85R16 and 4:10 rear end gears on the highway I was lucky to get 7-8 mpg.
Swapped out the rear end gears for a set of DANA/SPICER 3:54's as well as a GEARVENDORS OVERDRIVE UNIT which when engaged gives me the equivalent of a 2:77 rear end.
Highway mileage is now 15-17 mpg depending on how much lead has filled my go-pedal foot.

SCOTI · 10-23-2015, 09:30 AM

8-9mpg's on the factory motor in my 89 (454/th400/4.10's/no OD/235-85-16's).
It's rebuilt now but haven't done highway miles to see if things are better now that it's fresh.

95 S_Trucker · 10-23-2015, 09:34 AM

Even the newer FI engines get bad mileage. My 99 with overdrive and 3.73 never gets better than 12. Its usually 9-11. But it stays at 9-11 when I tow.

If you buy a big block truck, you're not buying it for fuel mileage. I tell myself that every time I put gas in it.

jjmorrse · 10-23-2015, 02:18 PM

I think it is easier with the monster to measure in terms of gallon per mile,which is about 0.2 gpm

10-23-2015, 02:03 AM	#1
DustyNova Registered User Join Date: Mar 2014 Location: Salt Lake City Posts: 128	427 Crew cab mpg question What do you guys usually get for 427/454s in your crew cabs?

10-23-2015, 03:09 AM	#2
BLE 'BURBAN In the Forgotten far North. Join Date: Jul 2007 Location: Anchorage, Alaska Posts: 2,627	Re: 427 Crew cab mpg question 87 cc dually,454/TH400 RWD running stock size 215/85R16 and 4:10 rear end gears on the highway I was lucky to get 7-8 mpg. Swapped out the rear end gears for a set of DANA/SPICER 3:54's as well as a GEARVENDORS OVERDRIVE UNIT which when engaged gives me the equivalent of a 2:77 rear end. Highway mileage is now 15-17 mpg depending on how much lead has filled my go-pedal foot. __________________ 1987 R3500 CREW CAB DUALLY (BIG RED)Acquired 06/12/2015 1990 chevy suburban V2500 5.7L My cluster Mods-Nov 2007 overhead console Stereo install Round 2 Aug 2009 Heated/turn signal mirror upgrade

10-23-2015, 09:30 AM	#3
SCOTI Registered User Join Date: Apr 2001 Location: DALLAS,TX Posts: 22,071	Re: 427 Crew cab mpg question 8-9mpg's on the factory motor in my 89 (454/th400/4.10's/no OD/235-85-16's). It's rebuilt now but haven't done highway miles to see if things are better now that it's fresh. __________________ 67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... *Cubic inches is like Indiana Jones with a cheap pistol.*

10-23-2015, 09:34 AM	#4
95 S_Trucker Registered User Join Date: Oct 2009 Location: . Posts: 2,187	Re: 427 Crew cab mpg question Even the newer FI engines get bad mileage. My 99 with overdrive and 3.73 never gets better than 12. Its usually 9-11. But it stays at 9-11 when I tow. If you buy a big block truck, you're not buying it for fuel mileage. I tell myself that every time I put gas in it.

10-23-2015, 02:18 PM	#5
jjmorrse Registered User Join Date: Aug 2010 Location: east tx Posts: 128	Re: 427 Crew cab mpg question I think it is easier with the monster to measure in terms of gallon per mile,which is about 0.2 gpm __________________ jjmorrse 86 C30 crewcab big dooley. 454- 400



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