TH 400 1st gear?

[Dano]

Been "advised" much concerning correct 1st gear needs for my 3500 lb car with 5.14 gears and 30" tire, behind a decent BB chev Stocker and TH 400 trans. Any "rule of thumb" I should be using?

[Jim Kaekel]

Originally Posted by Dano

Been "advised" much concerning correct 1st gear needs for my 3500 lb car with 5.14 gears and 30" tire, behind a decent BB chev Stocker and TH 400 trans. Any "rule of thumb" I should be using?

You didn't say if it's a Stocker, S/S or bracket car but the stock 2.48 is a good starting point. Keep in mind that we're racing at least 1/8 or 1/4 mile and not just to the 60'. A close ratio trans may result in a slower 60' time but due to less RPM drop on gear changes, could result in a quicker E.T. On the other hand a trans with a wide ratio, say a 2.75 for example may provide a quicker 60' but may fall down too much on the gear change. Converter stall also comes into this discussion as well.

[Glenn Briglio]

Originally Posted by Jim Kaekel

You didn't say if it's a Stocker, S/S or bracket car but the stock 2.48 is a good starting point. Keep in mind that we're racing at least 1/8 or 1/4 mile and not just to the 60'. A close ratio trans may result in a slower 60' time but due to less RPM drop on gear changes, could result in a quicker E.T. On the other hand a trans with a wide ratio, say a 2.75 for example may provide a quicker 60' but may fall down too much on the gear change. Converter stall also comes into this discussion as well.

Says BB chev stocker

[Dano]

Originally Posted by Jim Kaekel

You didn't say if it's a Stocker, S/S or bracket car but the stock 2.48 is a good starting point. Keep in mind that we're racing at least 1/8 or 1/4 mile and not just to the 60'. A close ratio trans may result in a slower 60' time but due to less RPM drop on gear changes, could result in a quicker E.T. On the other hand a trans with a wide ratio, say a 2.75 for example may provide a quicker 60' but may fall down too much on the gear change. Converter stall also comes into this discussion as well.

Have been told about the "fall Down" several times. Converter is a ATI 8" set up pretty loose. Haven't run it yet but anticipating a flash of around 5800-6000 rpm. I wish cost wasn't an issue, but of course it is......making the mistake on the ratio is concerning. Have been looking at the Coan LW 400 with the 2.48....and comparing with same trans with the 2.75. any way to determine existing trans 1st ratio? It's a Kilgore deal, recently freshened locally, but the trans guy said he couldn't tell and Kilgore "couldn't" locate original build paperwork.

[Pedigo Perf]

What class and combo BBC?

[Dano]

Originally Posted by Pedigo Perf

What class and combo BBC?

70 Nova.....B/SA....402", GM 401 Alum Head

[Painter]

Turbo 200 with 2.75 low, swap converter for one for a 200. Put the 400 in a pick up truck where it belongs. The fast big blocks are successfully run in 200s.

[Mark Yacavone]

Originally Posted by Painter

Turbo 200 with 2.75 low, swap converter for one for a 200. Put the 400 in a pick up truck where it belongs. The fast big blocks are successfully run in 200s.

..Or 33.5' Class A 454 motor home, like the last one I built for anything ;-)

[Tim H]

Originally Posted by Painter

Turbo 200 with 2.75 low, swap converter for one for a 200. Put the 400 in a pick up truck where it belongs. The fast big blocks are successfully run in 200s.

Or sell TH400 to bracket racer, I ran my TH400 for many seasons no issues @ 700hp and 2900lbs.

[Dano]

Originally Posted by Mark Yacavone

..Or 33.5' Class A 454 motor home, like the last one I built for anything ;-)

so much for defending stock racers as being snobby.....LOL