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Cruising RPM ?

65-440

65-440

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Ok, finally temp wired a tach just to get a baseline reading now that my 3.23's are fully broke in. Had my wife write down the readings. I'm pretty sure the tach is accurate, if compared it with my digital timing light at idle, but these seem low too me ! 383, 727, 275/60 rear tire, 3.23 gear .... here's my speed/ RPM and vac readings

20180121_162714.jpg
 
I threw a couple of them in the calculator at Wallace racing site and it was pretty close, 70mph calculated at 27** rpm.
 
Real. TKO 5. 3:54 Dana. 2150 @ 70 mph.
 
If at 35 mph your turning 1,500 rpm then at 70 mph you should be turning about 3,000 rpm doing the simple math. It appears something is a little off, could be tach, could be speedo, could be both, could be what?
 
Looks like I'm good to go then. I just expected more RPM, I'm used to my 340 4spd dart with 255/60 and 3.55 gears turning 3k at 65mph ! My Speedo is very close compared to gps, tach is What it is ... but based off you guys and the calculators there is a very minimal difference in what I wrote down and the calculators.
 
Numbers look about right; it could be a problem with your ears/brain after years of overdrive and 2.50-2.76 rear ends and better sound insulation?
 
Dibbons said:
If at 35 mph your turning 1,500 rpm then at 70 mph you should be turning about 3,000 rpm doing the simple math. It appears something is a little off, could be tach, could be speedo, could be both, could be what?
Click to expand...
Maybe it had not shifted gears yet and the fact at lower rpms there is more converter slippage.
 
Those numbers look about right to me as well. I turn
2800 @ 70
2600 @ 65
2400 @ 60
with a 4 speed and a 3.23 on 245/60/15's
 
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