Trans brake and delay box question(s)

Posted By: dodge340dart

Trans brake and delay box question(s) - 07/28/13 06:37 PM

After racing the last two seasons in a .500 pro tree bracket racing eliminator and winning the track championship both years I have decided to move to another class. This is based upon the fact that the car count has dropped so low that the payout even when you win puts you at a major loss for the night. I have been footbraking the Dart since I started racing in 2001 and while I am decent on a sportsman tree I am very good on a pro tree, I am thinking of moving to super pro so I can react to the top bulb similar to a pro tree reaction. I have to add a transbrake and a delay box and while I have a good idea of what to do I would like some input from those who have used these in the past. I have a '69 Dart that weighs 3033lbs with me in it; the Dart 60fts around 1.50 and run the quarter at about 11.40 at 115mph. It is a 340 with a 904LBA reverse manual and an 8 3/4" with 4.10 gears. I footbrake the Dart to 3500RPM and slam the pedal to the floor on the flash of yellow, the converter (PTC 9.5") flashes to 4800RPM and I am off. I averaged a .024RT for two years with this technique.

So what mods do I need to perform to my transmission or car? Should I move the vent? Do I need to go to billet drums? 4 clutch packs? 5 clutch packs? Drill additional vent holes? Modify the pump? If I hold the RPM to 3500-4000RPM on the transbrake will the 8 3/4" have similar impact on it as when I footbraked?

Any input would be great.

Thanks,

Chris

Posted By: 70AARcuda

Re: Trans brake and delay box question(s) - 07/28/13 06:58 PM

Quote:

After racing the last two seasons in a .500 pro tree bracket racing eliminator and winning the track championship both years I have decided to move to another class. This is based upon the fact that the car count has dropped so low that the payout even when you win puts you at a major loss for the night. I have been footbraking the Dart since I started racing in 2001 and while I am decent on a sportsman tree I am very good on a pro tree, I am thinking of moving to super pro so I can react to the top bulb similar to a pro tree reaction. I have to add a transbrake and a delay box and while I have a good idea of what to do I would like some input from those who have used these in the past. I have a '69 Dart that weighs 3033lbs with me in it; the Dart 60fts around 1.50 and run the quarter at about 11.40 at 115mph. It is a 340 with a 904LBA reverse manual and an 8 3/4" with 4.10 gears. I footbrake the Dart to 3500RPM and slam the pedal to the floor on the flash of yellow, the converter (PTC 9.5") flashes to 4800RPM and I am off. I averaged a .024RT for two years with this technique.

So what mods do I need to perform to my transmission or car? Should I move the vent? Do I need to go to billet drums? 4 clutch packs? 5 clutch packs? Drill additional vent holes? Modify the pump? If I hold the RPM to 3500-4000RPM on the transbrake will the 8 3/4" have similar impact on it as when I footbraked?

Any input would be great.

Thanks,

Chris

I have 3 904 with brakes in use, I use Tranzact Pro Brakes, I would use 5 disc in front drum, if you use the thin disc and steels 5 disc can be put in the standard 4 disc drum. The 904 front drum does not explode like the 727, so a billet drum is not required. I would recommend upgrading to the 24 spring kit in the front drum and get rid of the large single wound spring.

I have left the vent in the stock location and have done no modifications to the pump.

I also use a msd 2 step to control the rpms on the starting line...The cars use 8 3/4 rear and weight from 2700 lbs to 3000 lbs with driver.

Posted By: Cab_Burge

Re: Trans brake and delay box question(s) - 07/28/13 10:03 PM

I would make sure your converter is built properly for a transbrake first

Posted By: MR_P_BODY

Re: Trans brake and delay box question(s) - 07/28/13 10:23 PM

Quote:

I would make sure your converter is built properly for a transbrake first

I dont think thats gonna be a problem.. looking at his
numbers he isnt making a ton of torque so that conv
should be able to handle it just fine.. even without
anti ballooning plates

Posted By: dodge340dart

Re: Trans brake and delay box question(s) - 07/31/13 12:11 AM

Thanks for the input. I am still questioning if the 489 case 8 3/4" with a bearing spacer will be strong enough to handle a 3500RPM launch on the transbrake. Is leaving off a transbrake at 3500RPM a similar impact on the drivetrain as footbraking at 3500RPM? Any thoughts?

Thanks,

Chris

Posted By: cgall

Re: Trans brake and delay box question(s) - 07/31/13 01:56 AM

Just go run S/P with what you got. If your car is within .01 every run, you are already at a .034 package. If you drive the finish line well, you can do well in S/P against those dreaded 7.70 dragster guys. Trust me, they are far from .00 and dead-on every run.

Posted By: MR_P_BODY

Re: Trans brake and delay box question(s) - 07/31/13 02:02 AM

Quote:

Thanks for the input. I am still questioning if the 489 case 8 3/4" with a bearing spacer will be strong enough to handle a 3500RPM launch on the transbrake. Is leaving off a transbrake at 3500RPM a similar impact on the drivetrain as footbraking at 3500RPM? Any thoughts?

Thanks,

Chris

Its the same impact but it happens quicker
EDIT
I hope you have that 8 3/4 back braced

Posted By: CHAPPER

Trans brake and delay box question(s)