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

Re: rpms = speed
 

It could be right, depends on tire size and rear gear ratio.

Re: rpms = speed
 

Re: rpms = speed
 

Its a '69 chey 1/2 ton pickup. My mechanic says its the stock rearend for that year. 15 inch tires.

Re: rpms = speed
 

How tall are the actual tires? Rim height makes no difference in rpm's. Also, is it an automatic or manual 3 speed?

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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,,,

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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Yea I think he said a 3.08,,,,,,,, he was surprised

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if you have a smart phone you can dl a speedometer app,,there pretty accurate

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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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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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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,,,,

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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Thanks,,,,he was more concerned about it staying steady,,,,or dropping out,,,,

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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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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,,,,