Footbraking the car do you go up on the converter or off idle and why do you do what you do. Also does one way or the other get you a better 60ft? On my previous 64 car which was lighter then my current car I left at idle and had a better 60ft (1.36) and et then if I tried to go up on the converter. However I think leaving off idle has an impact on my RT and not being consistent. So lets hear it and thanks!!!


Russ

Russ,
I can "true" foot brake, no box or box with very little (and quick) changes. Any of the three ways, I leave at 3000 RPMs. One benefit is that I can compare runs "apples to apples".
When I foot brake, I some times have to give HUGE spots. (I'm 10.65, spotted racers 7 & 8 sec), but even being on the converter for 8 seconds, my 60' times are consistant as are my reaction times.
When I have messed up and left at basicly an idle (1800-2000) my 60' is OK, but the reaction times are real bad (.2) I usually have plenty of time to reflect upon that gaff.
The key is to do the same thing EVERY time.

Brian Dunnigan

Hey Russ. The question of which way nets the best 60 ft depends partly on your converter and how well you have your carb tuned for leaving off idle. I personally always set my carb up to get max pump shot AFTER the throttle blade was past the transition slots, which was usually about 2500 rpm's. This always took the headache out of trying to get it to leave "clean", and with the usual 4500 plus race converters holding it at 2500 was easy. You'll get dozens of diff approaches/opinions, but this is how I chose to do it and my car was always VERY consistant on the 60's. I was never one to "timeslip race", just looking for consistancy.
Ken.

I tried leaving off a dead idle years ago and RT and ET was too inconsistent.

I leave around 2600 RPM with my car.

Bringing it up on the convertor also preloads the driveline a little. I think it helps. Seems to take any play out of the system on the launch, and is very consistent. Launch rpm depends on your convertor. A drastic change in 60ft from launching one way or the other is probably the squirter shot arms not adjusted right on the carb. When the carb is at idle, there should be 0.00" to 0.004" gap between the pump arm and the head of the bolt with the spring on it that pushes it down to open the squirter shot. Do not have either the front or rear preloaded when at idle. If you change you idle screw, this has to be reset.

Off-idle or on the converter - 60' times have a lot to do with how the carb and whole car overall are set up.

I put priority on RT's so I stage and launch in a way that produces the best, most consistent reaction times for me. I actually stage at idle, THEN bring it up to 3,300-3,500 and launch at the first hint of 3rd yellow. Some people stage and launch around idle while others come up on the converter and bump in with the rpm's up already. You have to be fast and ready my way because you can get caught not ready with the lights coming down while bringing the rpm's up when staged. There is no "best" way. Too may variables and what's comfortable for each driver.

I actually lose a little 60' when I bring the rpm's up after staging. When the rpm's go up and the suspension tenses up, it actually rolls a little forward and "loads" the suspension. Less "slop" and movement is available to use up time. If I staged shallow and launched at the rpm I staged at, 60' would be better IF the carb and rest of the car was set up to work well that way. Mine does not work well from idle. Each car and driver will be different.

If you find a comfortable spot to launch and have consistent RT's and 60's, but not necessarily "good" RT's, you can alter it by a few hundredths with different tire diameters and then fine-tune it with tire pressures.

Taller tires and less air pressure = more rollout, faster 60' and slower RT.

Shorter tires and more air pressure = less rollout, slower 60' and faster RT.

This is if you do EVERYTHING the same way and put the car in the same spot every time. You can change the launch rpm also to change the RT a bit. Raising it after staging will roll the car in a bit and a higher rpm will provide a little less rpm range and time for the converter to lock up when you launch for slightly quicker RT's.

Squirters and pump cams for 60' and jet for mph.
Consistent water temperatures after the engine is heat-soaked, is also important to provide accurate results from changes to anything with the engine. A car launching with water at 120* will tend to react differently than at 160*.
Different temps can lean or richen the accellerator pump circuit from optimum. The higher you come up on the converter, the less fuel is left in the accellerator pump circuit to squirt when you floor it. Lots you have to be aware of and tune for. Too much fuel being introduced initially at launch can make the car sluggish (rich) just like not enough can make it bog (lean). Duration of the squirt can do the same.

All can affect 60' and RT's.

Leaving off of a trans brake of just a 2-step is easier for RT's but, again, it depends on the whole car set-up whether or not it works better than footbraking for 60' times.

Boy, that got long quick!

I turn on the first bulb and take the slack out of the car. Turn on the second bulb and go up to my launch rpm. To me the rt is the most important aspect along with consistant 60' times.

The converter size and chassis will react different on every car, test yours to find out what you and the car do the best with some of the cars I have raced and owned like 2300 to 3100 RPM( 8 inch converter, leaf springs and ladder bars both ) and some of them like lower and higher RPM

I`m just an et chaser but my car 60`s better and has the best EVERYTHING leaving around 2800-3000 rpm`s............tried lower tried higher w/lesser results.

i will add a little to what Myron said..
the pump shot is key to the 60ft..
if you bring the car up on above idle rpms...you employee less pump shot when the car leaves..
you may need that to get the better 60ft..
it may need to be bigger shot initially or a longer more gradual shot...
obviously your engine will want what it wants..
but if you get good 60s off idle and they drop off when you stall more rpm at the launch..
then you may need the pump shot to keep a good 60 ft...pump cams,squiters and diaphrams can change/move/fix this.
fwiw...something to consider.

to make my car super compeditive in footbrake and nobox heavy/pro in local 1/8. raised idle to 1,250 hold converter at 2,500 rpm, got tighter converter,taller slicks,got twin 50 cc pumps on 660 center squirt t-ram carbs, did same count to 8 second high gear burnout everytime,same temp in motor and same tire pressure. car was deadly on and feared 5.05 lights all the time, 1/2 races were won at tree and 60 foot, and in finals always had free round for lowest reaction time.

Kevin is the hired gun in the car, but it depends on what we are running. In nostalgic super stock, they run a 4/10's full tree so we put on a short tire and depending on what motor is in the car he will go up on the convertor between 2000-2800 to change his reaction time. On a 5/10 tree with a taller tire, the launch rpm is slightly lower. ET and 60' are better off-idle, but this is bracket racing. We don't care about ET, just reaction time and consistency.

Good post...I have a heck of a time if I stage 2nd and have to bring my RPMs up to 2500 or whatever before the lights start falling. Just too much to watch for me. I'm not that experienced....so I've been leaving off the 2 step set a 2500. But I tend to get worse 60' times like this.

I light the first bulb bring the rpm's up to 2000 hold it there and bump in shallow, leaving at the same 2000. Depending on the track, if my rt are slow I'll bump in a little deeper.
Yea I have have no idea how much deeper but...

in my experience the lower the rpm the better the 60ft

When I run a double pumper carb, I can leave at lower rpms; 2200-2400 and let the converter flash help the 60'. With a vacuum secondary carb it likes 3500-3800 - I think that it helps get the secondaries in sooner.