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01-18-2010, 12:46 AM
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#1 |
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Registered User
Join Date: Nov 2008
Location: Gwinnett GA
Posts: 1,803
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Best RPM for highway driving? Tires too?
I just installed a tach on my '87 K20, and I was wondering what the best rpm for mileage is on the highway. Now I know 1800 rpm is usually best but the highway near me is really hilly, and I need lots of throttel below 2krpm to climb hills, resulting in worse mpg. Is 2500 rpm too high for good mpg?
Also, I currently have 245/75r16 tires, and am soon due for new ones, I'm wanting something a little taller looking to fill the wheel wells just a little better, what tire size? 235/85 looks ok on other trucks... what do you think? The truck in question is an 87 TBI350, 3.42 gears and 4 speed granny transmission, seems to run 2200rpm or so at 60mph, who knows how accurate the speedo is, thanks for the input. 
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1982 K10 SWB 1987 V20 - Sold - Doh! |
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01-18-2010, 12:50 AM
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#2 |
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Account Suspended
Join Date: Jul 2008
Location: Where I come from, it's cornbread and chicken...
Posts: 3,122
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Re: Best RPM for highway driving? Tires too?
My C20 crewcab has 235/85/16s on it, don't have any pics with the motor in it or the bed on it or I'd post it...the tire size is a nice size...
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01-18-2010, 12:59 AM
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#3 |
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Registered User
Join Date: Nov 2009
Location: goodland,ks
Posts: 217
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Re: Best RPM for highway driving? Tires too?
i would say between 2200 to 2500 is good but what do i know BTW that is a nice truck!!
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01-18-2010, 01:15 AM
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#4 |
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Badass
Join Date: Jan 2009
Location: lox. fl
Posts: 4,586
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Re: Best RPM for highway driving? Tires too?
i did 3k rpms for 4hours straight (well 2 stops for gas) didnt have a problem
__________________
Think outside the box? -84c10 (1stcar)→My Build←  -00 Saturn 5spd drop a gear and disappear! 1/4:13:90 
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01-18-2010, 01:34 AM
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#5 |
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Registered User
Join Date: May 2009
Location: Washington
Posts: 663
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Re: Best RPM for highway driving? Tires too?
285/75r16 FTW.
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01-18-2010, 11:04 AM
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#6 |
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Watchin the rust grow
 
Join Date: Oct 2008
Location: Western Nebraska
Posts: 950
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Re: Best RPM for highway driving? Tires too?
I like the 32x10.5R15's
2300 at 55 for an hour last night........gas suckin.
__________________
1979 Chevy K10 (H/D Front end) - 350 w/ Holley Truck Avenger, Weinald Intake manifold, headers, bored .060 over, mild cam, Built up TH350 (TranStar Shift kit) with a part-timed NP203 t-case SOLD ($3,000) 1997 Chevy Silverado 1500 - 4.3 vortec, extended cab, 21 highway MPG, stock. "Red" SOLD ($3,000) 1987 Toyota 4wd Pick-up - work in progress, future DD SOLD ($1,850) 1998 Dodge Ram 2500 Cummins 5spd Quad cab - old 12 valve with some work done  2004 Chevy Silverado - Black, 4x4, 5.3L, stock for now Underneath that rust is a heart of gold
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01-18-2010, 01:08 PM
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#7 |
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Registered User
Join Date: Mar 2008
Location: Salt Lake City UT
Posts: 441
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Re: Best RPM for highway driving? Tires too?
Bear in mind if you install "taller" tires, the overall gear ratio will change.
Best way to determine the engine's most efficient rpm (without using a dyno) is to determine the cam specs and find out where the torque curve is. Hopefully you'll be into the front half of the curve at the road speed you'll most often drive. Last edited by dan76; 01-18-2010 at 01:10 PM. |
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