Editing Openai/695c4a9d-28a0-800d-9f93-cab63ec35c09 (section)

=== Assistant: Great question — this is one of those drag-racing terms everyone uses but rarely explains clearly. ===
Great question — this is one of those drag-racing terms everyone uses but rarely explains clearly.

I’ll explain it plain English first, then tie it directly to your Buick + TH400 combo.

==== A loose torque converter is one that: ====
* Allows the engine to rev higher before the car really starts moving
* Slips more under load
* Multiplies torque more aggressively at launch

Opposite:
* A tight converter grabs earlier, slips less, feels more “direct”

==== ### ====
* Engine revs up quickly on launch
* Car may feel “soft” for a split second, then pulls hard
* Higher RPM at the finish line than the math says
* More heat generated
* Better for heavy cars and big torque motors

===== - Car moves immediately with throttle =====
* Lower RPM at the stripe
* Less heat
* Better for highway and mild combos

==== ### ====

The RPM where the converter stops slipping and starts pushing the car hard.

There are TWO stalls:
* Flash stall (what racers care about)
* Footbrake stall (what you see on the line)

Your:
* Footbrake: ~2,000 rpm
* Flash stall (estimated): 3,200–3,600 rpm

That difference = looseness.

==== We know it is because: ====

===== Math says ~4,900 rpm =====
You see ~6,000 rpm

That’s 20%+ slip at the top end — classic loose converter behavior.

===== Big-block Buicks: =====
* Make huge torque early
* Push converters harder than Chevys
* “Act looser” than rated stall

So a “3,200” converter in a Chevy might act like a 3,600–3,800 in your car.

==== For your setup: ====
* Heavy-ish car
* Big torque
* Footbrake launch
* Drag radials

A loose converter:
* Helps you leave cleanly
* Keeps the engine in the torque curve
* Explains your strong 60-ft times

Your 1.47–1.49 60-ft proves it’s working.

==== At the top end: ====
* Excess slip = lost MPH
* Gear + loose converter = RPM ceiling
* Engine works harder than necessary

That’s why:
* MPH is capped at ~99 in the 1/8
* You’re at 6,000 RPM early

==== You don’t want: ====
* Super tight (kills 60-ft)
* Super loose (kills MPH)

For your Buick / TH400 / 28" tire:
* Ideal flash stall: 3,200–3,400
* Stripe slip: 10–12%, not 20%+

You’re currently looser than ideal for maximum MPH.

==== ### ====

Going from 4.10 → 3.73 or 3.55:
* Reduces load on converter
* Lowers slip
* Picks up MPH
* Often keeps ET the same or better

This is the cheapest, smartest move.

===== Manual shifting: =====
* Reduces flare during shifts
* Helps the converter couple sooner
* Stabilizes RPM

Free ET and MPH.

==== Only if: ====
* You go faster than 10.50
* Or add more cam / RPM
* Or go transbrake

Right now:
👉 Your converter is helping more than hurting — the gear is the bigger mismatch.

==== Loose converter = more RPM slip under load ====

In your car:
* Great for launch ✅
* Hurting MPH ❌
* Fixable with gearing and shift strategy ✔️

If you want next, I can:
* Estimate your actual flash stall
* Or tell you exactly what converter spec would be perfect if you ever change it