[Lee]

Originally Posted by ponyakr

Since I raced a 4-speed car for a few years, I'll take a stab at this one.

You experiment with shift points, til you find those which produce the lowest ET. Without actual, on track testing, all you have are opinions. And, as we've seen on this and most every forum, opinions can differ WIDELY, on most any given subject.

There can be too many variables with engine & cam torque & power numbers, trans & rear gear ratios, etc.

I totally agree. After running a wide variety of cars at the track, and having tested several of them on a chassis dyno, the track testing is THE way to figure it out.

One variable I've not seen mentioned, is the tachometer. Not all are accurate. Not all respond as quickly as the engine rpm actually changes.

My FIRST 455 I ever totally built, was in the very early 90's. I bought the block & crank, all parts, all machine work, and rented an engine hoist for under $1,500. That was my tax refund that year, and was ALL the money I could spend. In a '79 T/A, stock torque converter, Q-jet, pre-EGR iron intake, and 2.93 gears, it was running 13.8's shifting at 5,000rpm. On a whim, I tried shifting lower - eventually ran 13.2's shifting at 4,600. Between 4,600 and 5,000 rpm, THAT car would lose a solid half-second at the track.

I had an '03 Mach 1. It had a redline around 7,000 (DOHC motor). On the chassis dyno the HP peaked a bit after 6,000rpm. While the rest of the world were shifting these cars at close to redline, I started dropping shift points and running quicker. Totally stock except for stock-size Nitto DR's, I ran several 12.9's shifting at 6200rpm.

My old Falcon wagon had a 427 inch Windsor. I probably made close to hundred dyno pulls with that car, testing various things (intake manifolds, valve lash, air cleaners, timing, jetting, etc.) and it always made peak HP right around 6,200. Now, my instincts were that this motor should perform best when shifted around 6,500, MAYBE 6,600. But it always gave best e.t. and MPH when it shifted around 6,900-7,000. I retested several times, but always got the same results.

Some combos like short-shifting, others like to be revved. Some are not very sensitive to shift point, while others are hyper-sensitive.