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bpu699 bpu699 is offline
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Join Date: Apr 2007
Location: wisconsin
Posts: 1,810
Missed shifts... when is it an issues? Physics of it...

Read lots of posts on here about missed shifts....

Obviously if you bend valves, you did something bad. Need to redo the heads, rod bolts,rebuild, etc...

But what if you have no immediate damage? Leak down normal, car runs fine... then, whats the thought process... Hard to know what peak rpm was unless you have a datalogger...

Was doing some mental math for the fun of it...

If you are trying to up shift from 3-4, and hit 3-2 instead...

Say red line is 6500, and you usually shift below that....

You take your foot off the gas, RPM starts to decay immediately... By the time it slips into gear you have decayed from 6500 to 5500 or so...

Now, you pick the wrong gear...

If your cars speed stays exactly the same, you have RPM going up quite a bit. Could jump 33% or so. So, in theory, you are going from 5500 to 7500+

But, in reality, the motor immediately starts slowing the car down... So if you were going 100mph, you are decaying to 70mph or so... So you never get the full 33% RPM increase...

So, your motor doesnt spin up as much? No?

Long question made short... if you guys miss a shift yet the motor and valves seem fine... do you do a rebuild? And with a 5-2 I suspect the answer is different than a 3-2 (rather than a 3-4). 5-2 is a HUGE ratio difference. 3-2, not so much.

How do you assess the motor if there are no apparent issues? You can't reach rod bolts without a complete teardown...
Old 07-13-2017, 08:12 AM
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