Highway RPMs? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Smokin72on20s · 02-06-2005, 07:14 PM

what do you think my rpms would be at 65mph?
turbo 400 trans with 3.08 rearend 28" tall tires
also, whats a good rpm to be at at 65mph?

Fred T · 02-06-2005, 07:21 PM

You should be around 2500 rpm, figuring some tire radius loss due to the vehicle weight. Driving rpm range for a sbc is 1800-2800 rpm.

Longhorn Man · 02-06-2005, 08:01 PM

Here you go..
3.07 gears
28 inch tall tires (275/60R15 on 9 1/2 inch wide rims)
Th350 non lockup converter

And one lead foot.

Smokin72on20s · 02-06-2005, 09:40 PM

i will be doing alot of highway driving with my truck, should i get rid of the turbo 400 and get a 700r4? if i could be at 2000 rpms or so, it would be easier on my motor and i would get better mpg, so maybe 700r4?

CHEVY & GMC FOREVER · 02-06-2005, 10:01 PM

Is that all that trucks got???? 90 MPH lead footed??.

**kwmech** · 02-06-2005, 10:02 PM

I doubt it he's only tach'n 3500, he is almost outta gas though

**kwmech** · 02-06-2005, 10:04 PM

The 3.08s with a 700 will essentially make the rear axle a 2.21 final drive ratio.

CHEVY & GMC FOREVER · 02-06-2005, 10:13 PM

Hey longhorn man what type of engine and trans do you got in that thing??

Longhorn Man · 02-06-2005, 10:59 PM

well, i think that truck is sittin engineless at themoment...(sold to chevye about the time you were joining the board with a knocking 305) but back then it had a 355 with mild porting on 2.02 882 heads, a *500 lift edelbrock cam* with rhodes lifters, flat top pistons, an edelbrock dual roller timing chain, performer RPM intake, and at that time, an Edelbrock 600 cfm carb.
*The guy i bought the engine off lost the cam card, and couldn't remember the specs, all he remembered was it was 500intake/501 exhaust...when i killed the engine I pulled it out and it did in fact have some HUGE lobes, but I couldn't verify anything.*
The tranny was a stock Th350 with a 1900 RPM B&M converter. Not enough converter to let her idle in gear, but with the 3.07 gears, I couldn't put the converter that the cam needed, so i ended up popping it in neutral at every stop light...that gets old after 3 1/2 years.
That thing wasn't all that great off the line...it had enough to make some smoke...but it really shined out on the open road.

I had it wrapped to the M in MPH once, and still had RPMs to go, but I was on a 2 lane black top in texas (commonly refered to as a Farm to Market rd) which was way too narrow and hilly to be playing around like that on so i lifted. I took a pic of the speedo, but that was in the 35mm camera days, and the camera ended up doing a gravity check and the pic was ruined...along with 6 months worth of truck pics.
That pic up there wasn't maxed out by far...I had to lift for the off ramp i was quickly headed to...that was here in Columbus a couple years ago. When i picked up the camera I was doin a hair over 100, but by the time I turned it on and it took the pic, I was already down to 92-ish.

Longhorn Man · 02-06-2005, 11:06 PM

BTW, back to the question at hand...smokin...honestly I never thought that 'normal' freeway driving was very bad at 2500 RPM. That was high enough to have some good power, yet low enough to get somewhat decent MPG...esp considering the engein that thing had in it. I got an average (both city/highway) of about 11 MPG, a best of 14 MPG (all freeway holding at 75 or so) and a low of 9 havin fun in town stop light to stop light.
It would take a whole lot of cruising to make the 700 pay it's self off, and it won't last nearly as long as a stock TH350 or TH400 would. (90% of the time this is correct, but there is that 10%...)
There is the cool factor, and the minimal engine longevity factor...I say minimal becouse 2500 isn't all that hard on a motor.

4x4Poet · 02-07-2005, 01:18 AM

Quote:

Originally Posted by Longhorn Man

...and the minimal engine longevity factor...I say minimal becouse 2500 isn't all that hard on a motor.

I sure hope not! My K10 has 3.73 gears and I expect the 350 (fresh rebuild) to turn ~3000rpm all day long @ 75mph on freeway trips with 32-11.50-15s. You 2wd guys crack me up.

Longhorn Man · 02-07-2005, 01:32 AM

Yup...I know what you mean...my truck has 31 inch tall tires and 4.10's in the diff.

powell72 · 02-07-2005, 02:58 AM

3.08's with a 700R4 might be lugging it down a bit unless your really haulin'

1972 · 02-07-2005, 03:14 AM

Quote:

Originally Posted by Smokin72on20s

what do you think my rpms would be at 65mph?
turbo 400 trans with 3.08 rearend 28" tall tires
also, whats a good rpm to be at at 65mph?

http://www.tyres1.com/calculators.html
Enter "1" for transfer case ratio if you have a 2wd.

lloyd k · 02-07-2005, 03:27 AM

you should step up to big block gm land with a 273 and 472 cadillac to go too upper regions of freeway driving

02-06-2005, 07:14 PM	#1
Smokin72on20s Ebay Junky Join Date: Oct 2003 Location: CO Posts: 893	Highway RPMs? what do you think my rpms would be at 65mph? turbo 400 trans with 3.08 rearend 28" tall tires also, whats a good rpm to be at at 65mph? __________________ 1972 CHEVY C-10 SWB 2WD - Possible Typhoon 4.3 turbo drivetrain.. 1983 Chevy c10 swb 2wd - possible 350tbi supercharged...

02-06-2005, 07:21 PM	#2
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	You should be around 2500 rpm, figuring some tire radius loss due to the vehicle weight. Driving rpm range for a sbc is 1800-2800 rpm. __________________ Fred There is no such thing as too much cam...just not enough engine.

02-06-2005, 09:40 PM	#4
Smokin72on20s Ebay Junky Join Date: Oct 2003 Location: CO Posts: 893	i will be doing alot of highway driving with my truck, should i get rid of the turbo 400 and get a 700r4? if i could be at 2000 rpms or so, it would be easier on my motor and i would get better mpg, so maybe 700r4? __________________ 1972 CHEVY C-10 SWB 2WD - Possible Typhoon 4.3 turbo drivetrain.. 1983 Chevy c10 swb 2wd - possible 350tbi supercharged...

02-06-2005, 10:01 PM	#5
CHEVY & GMC FOREVER Registered User Join Date: Nov 2004 Location: New Lenox,IL Posts: 306	Is that all that trucks got???? 90 MPH lead footed??. __________________ 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

02-06-2005, 10:02 PM	#6
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,499	I doubt it he's only tach'n 3500, he is almost outta gas though Last edited by kwmech; 02-06-2005 at 10:05 PM.

02-06-2005, 08:01 PM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Here you go.. 3.07 gears 28 inch tall tires (275/60R15 on 9 1/2 inch wide rims) Th350 non lockup converter And one lead foot.

02-06-2005, 10:04 PM	#7
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,499	The 3.08s with a 700 will essentially make the rear axle a 2.21 final drive ratio.

02-06-2005, 10:13 PM	#8
CHEVY & GMC FOREVER Registered User Join Date: Nov 2004 Location: New Lenox,IL Posts: 306	Hey longhorn man what type of engine and trans do you got in that thing?? __________________ 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

02-06-2005, 10:59 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	well, i think that truck is sittin engineless at themoment...(sold to chevye about the time you were joining the board with a knocking 305) but back then it had a 355 with mild porting on 2.02 882 heads, a 500 lift edelbrock cam with rhodes lifters, flat top pistons, an edelbrock dual roller timing chain, performer RPM intake, and at that time, an Edelbrock 600 cfm carb. The guy i bought the engine off lost the cam card, and couldn't remember the specs, all he remembered was it was 500intake/501 exhaust...when i killed the engine I pulled it out and it did in fact have some HUGE lobes, but I couldn't verify anything. The tranny was a stock Th350 with a 1900 RPM B&M converter. Not enough converter to let her idle in gear, but with the 3.07 gears, I couldn't put the converter that the cam needed, so i ended up popping it in neutral at every stop light...that gets old after 3 1/2 years. That thing wasn't all that great off the line...it had enough to make some smoke...but it really shined out on the open road. I had it wrapped to the M in MPH once, and still had RPMs to go, but I was on a 2 lane black top in texas (commonly refered to as a Farm to Market rd) which was way too narrow and hilly to be playing around like that on so i lifted. I took a pic of the speedo, but that was in the 35mm camera days, and the camera ended up doing a gravity check and the pic was ruined...along with 6 months worth of truck pics. That pic up there wasn't maxed out by far...I had to lift for the off ramp i was quickly headed to...that was here in Columbus a couple years ago. When i picked up the camera I was doin a hair over 100, but by the time I turned it on and it took the pic, I was already down to 92-ish.

02-06-2005, 11:06 PM	#10
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	BTW, back to the question at hand...smokin...honestly I never thought that 'normal' freeway driving was very bad at 2500 RPM. That was high enough to have some good power, yet low enough to get somewhat decent MPG...esp considering the engein that thing had in it. I got an average (both city/highway) of about 11 MPG, a best of 14 MPG (all freeway holding at 75 or so) and a low of 9 havin fun in town stop light to stop light. It would take a whole lot of cruising to make the 700 pay it's self off, and it won't last nearly as long as a stock TH350 or TH400 would. (90% of the time this is correct, but there is that 10%...) There is the cool factor, and the minimal engine longevity factor...I say minimal becouse 2500 isn't all that hard on a motor.

02-07-2005, 01:32 AM	#12
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Yup...I know what you mean...my truck has 31 inch tall tires and 4.10's in the diff.

02-07-2005, 02:58 AM	#13
powell72 Senior Member Join Date: Jan 2005 Location: Loveland Co. Posts: 3,098	3.08's with a 700R4 might be lugging it down a bit unless your really haulin' __________________ Chris 74 Custom Deluxe SWB 350/350/3.73’s 99 2wd Silverado RCSB 5.3/4L60/3.90’s http://www.classictrucks.com/feature...short_bed.html

02-07-2005, 03:27 AM	#15
lloyd k Registered User Join Date: Feb 2004 Location: columbus,ohio Posts: 201	you should step up to big block gm land with a 273 and 472 cadillac to go too upper regions of freeway driving

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.