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03-13-2015, 03:27 PM
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#1 |
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Registered User
Join Date: Jan 2015
Location: Hudson, fl
Posts: 118
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rpms = speed
I've got a 350 with 305 heads. At 2200 rpms,,,,shows I'm running 50 mph. Is that about right? Its got the 3 speed trans in it. Lets say I want to go out on the interstate,,,,can I run 70 and not hurt the engine? Thanks
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03-13-2015, 03:38 PM
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#2 |
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Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: rpms = speed
It could be right, depends on tire size and rear gear ratio.
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71 K20 64 GMC mud truck |
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03-13-2015, 04:14 PM
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#3 |
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Registered User
Join Date: Aug 2010
Location: Edwards, CA
Posts: 7,503
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Re: rpms = speed
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Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID ** Blazer SPID ** Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders ** Do you have a 1972 Plaid Pickup? ** Plaid Blazer ** Plaid Suburban |
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03-13-2015, 04:57 PM
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#4 |
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Registered User
Join Date: Jan 2015
Location: Hudson, fl
Posts: 118
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Re: rpms = speed
Its a '69 chey 1/2 ton pickup. My mechanic says its the stock rearend for that year. 15 inch tires.
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03-13-2015, 05:09 PM
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#5 | |
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Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: rpms = speed
Quote:
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71 K20 64 GMC mud truck |
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03-13-2015, 05:19 PM
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#6 |
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Registered User
Join Date: Jan 2015
Location: Hudson, fl
Posts: 118
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Re: rpms = speed
25in tire height,,,,its a 3 speed auto. Thats the next question,,,LOL. It really likes the gas,,,which is expected for the engine,,,could I change the transy out for,,say one with an overdrive in it,,,
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03-13-2015, 05:22 PM
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#7 |
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Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: rpms = speed
Using this calculator, I figure you either have 3.08 or 3.23 gears.
http://www.ringpinion.com/Calculators/Calc_RPM.aspx You could change the tranny out for say a 700r4, but is the expense really worth it?
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71 K20 64 GMC mud truck |
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03-13-2015, 06:23 PM
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#8 |
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Registered User
Join Date: Jan 2015
Location: Hudson, fl
Posts: 118
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Re: rpms = speed
Yea I think he said a 3.08,,,,,,,, he was surprised
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03-13-2015, 06:41 PM
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#9 |
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Registered User
 
Join Date: Jul 2010
Location: memphis
Posts: 2,537
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Re: rpms = speed
if you have a smart phone you can dl a speedometer app,,there pretty accurate
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1981 C-10 (Pop's) 1978 Camaro 2006 Lacrosse |
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03-13-2015, 07:08 PM
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#10 |
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Hittin E-Z Street on Mud Tires
Join Date: Nov 2004
Location: Greenville, SC
Posts: 23,090
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Re: rpms = speed
The majority of automatic trucks had a 3.08 rear, the majority of the 3 and 4 spds all came with 3.73 or 4.11 (mostly 3.73)... there's a chart somewhere... These trucks went 70 mph just fine when they were new.
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Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride  American Born, Country by the Grace of God  1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications! |
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03-13-2015, 08:08 PM
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#11 |
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Registered User
Join Date: Jan 2015
Location: Hudson, fl
Posts: 118
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Re: rpms = speed
Thanks,,,,I'll run it for awhile and see ,,,,, LOL,,,,of course,,,I'm not used to the gas being sucked in,,,. but the more horsepower,,,the more gas,,,,and it sure ****s and gits it,,,,LOL,,,,thanks for all the input,,,,,Bill here
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03-14-2015, 01:17 PM
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#12 |
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Registered User
Join Date: Jan 2015
Location: Hudson, fl
Posts: 118
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Re: rpms = speed
Hey,,,,more questions,,,,LOL. At idle,,,I'm pushing about 20lbs of oil pressure,,,at around 3k rpms,,,its steady at 38lbs,,,running 20/50 oil in it. Is this ok,,,,my mechanic says he thinks with the age of the engine,,,,the bearings might be worn,,,says if it goes lower or doesn't stay steady,,,we'll pull the engine and rebuild,,,,
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03-14-2015, 02:57 PM
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#13 |
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Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: rpms = speed
I've always heard 10lbs per 1k rpm is acceptable. It could be higher (mine pushes 45 psi at idle), but I don't think it's enough to really worry about.
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71 K20 64 GMC mud truck |
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03-14-2015, 03:06 PM
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#14 |
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Registered User
Join Date: Jan 2015
Location: Hudson, fl
Posts: 118
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Re: rpms = speed
Thanks,,,,he was more concerned about it staying steady,,,,or dropping out,,,,
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03-14-2015, 08:41 PM
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#15 |
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Registered User
Join Date: Dec 2014
Location: Newark, De
Posts: 58
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Re: rpms = speed
mine has a 350/sm465 4.57 rear and 265/75/16 tires. it used to have 245s and was worse. I usually drive around 75-80
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03-14-2015, 10:08 PM
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#16 |
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Registered User
Join Date: Jan 2015
Location: Hudson, fl
Posts: 118
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Re: rpms = speed
Tire on mine are Cooper Cobra,,,,P235/60 R15,,,,LOL,,,,jeeeez ,,,its been years since I drove a vehicle that had some damn horsepower and sound LOUD,,,,and no overdrive,,,,
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