average RPMs
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average RPMs
I'm looking to get a sense of average RPMs with a 400. i've not driven so many older cars or trucks so i'm a little surprised to see 4000 RPM goin about 50 down the highway, though i see many torque ratings at 5500 RPM.
Rebuilt 400 now .040 over
What are 'HIGH" RPMs with this 400 in 78 F150?
How fast can/ should i go down the highway?
i'm sos - stuck on stupid
Rebuilt 400 now .040 over
What are 'HIGH" RPMs with this 400 in 78 F150?
How fast can/ should i go down the highway?
i'm sos - stuck on stupid
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ya its a shucks tach from equus, the directions want it set at 4000 for a 8 cylinders - which i did. The coil is an aftermarket though.
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Post Fiend
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Is it a 4x4? Take it out of low range, or make sure you are actually in high gear..
3.55 gears and 31" tires would only net less than 2500 rpm. If you are getting 4K rpm, then the tach is telling you lies, or you are in low range, or the trans is not in the high gear.
3.55 gears and 31" tires would only net less than 2500 rpm. If you are getting 4K rpm, then the tach is telling you lies, or you are in low range, or the trans is not in the high gear.
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Post Fiend
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From: Big Sky Country
I'm not quite sure what you mean by "the directions want it set at 4000 for a 8 cylinders" most tachs (not all) have a setting on the back for 4,6 or 8cyl. if your tach has such a setting verify it's set to 8cyl.
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the tach has no number of cylinders setting : to adjust you turn off the igntion, hold the button in back to set the tach to 0, turn ignition on and then repeatedly push the rear button until the tach reads 4000 (for 8 cylinders). seems kinda flaky to me - could be the problem eh?
Truck is a 4x4 and in high
Truck is a 4x4 and in high
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From: Skyway, WA
Your transmission is shifting right? 4K RPM should sound like its about to blow up (well maybe thats a bit dramatic). Before I changed my rear end to a higher ratio, I had a 3.5 9" rear with 31" tires. 50mph was roughly 2K RPM give or take a couple hundred (I don't wanna do the math and don't remember precisely) Assuming you don't have an overdrive gear, or you have a low range transfer case and your not in low range, and assuming your speedo is accurate, knowing your rear gear ratio, tire diameter, and 60mph, you can calculate your RPM. Speaking of speedometer, is it accurate? Have you changed tire size from stock? If so, was the speedo gear changed and/or calibrated by a speedo shop? I'm most suspicious that the aftermarket tach isn't set up correctly combined with an inaccurate speedo reading.
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C6 tranny has just been rebuilt also, i get three shifts and the motor doesn't seem to be reving extermely high; so i'm going back to check my stuff : speedo and tach set correctly.
Thanks Everyone : sounds lije i surely got somethin goofy! and should be between 2000 and 2500 RPM @ 50 MPH.
Thanks Everyone : sounds lije i surely got somethin goofy! and should be between 2000 and 2500 RPM @ 50 MPH.