RPM launch suggestions
 

Was just looking for some info on launching my 461. I understand every combo is different but I thought I would get some ideas on where a solid starting point would be. What suggestions do you have and what RPM should I launch at? ??? My combo is…
..
461 340 heads 4L80 Holley terminator X
PTFB drop leaf springs….anti squat bars…Viking adjustables
MT E street R’s
Dyno numbers 610hp 600ftlbs

Thanks fellas

The hp and torque info you posted are useless without the rpm they where produced at, and that’s what matters most.

That makes sense…I will try and find and posted the dyno sheet with the curve……I figured the combo was a pretty common one and there was a general place I could start

How do the peak HP/TQ numbers from a dyno equate to the RPM the car should launch from?

I have a somewhat similar stroker combo that works out to about 525-550hp that peaked around 5400rpm... but after lots of low 11 sec runs at 121+mph, i found the car launches best off idle or maybe foot braked to around 1000-1200 rpm. With a continental 10" converter flashing to about 3300 it seems to work best off idle or very low rpm, if i try to launch at higher rpms 1500-1800 the M/T drag radial tires usually break free so bad the run is all but lost & 60ft sucks compared to off idle/low rpm. Using the same PTFB dropped leafs & their subframe connectors but no other traction aids besides a home made pinion snubber that does help a little.

I would say you really need to experiment with the car some to see where it launches best, play with the anti squat bar & shock adjustments as well as tire psi. But for my combo & others like it such as cliff r's old car, it made best times off idle for that combo, if you have a very high stall then higher rpm may work better. Just gotta play with it some at a couple test & tune events.

I'd heard 1000 rpm under converter stall speed. I got a new converter, did exactly that (4800), and put my car on the rear bumper for the first time. Hope you have better results.

Thank you guys….exactly the kind of info I was trying hear…. I have a triple lock up converter with a 3600 stall….I’m thinking with my torque I will start just off idle because I’ve given it around 2k before and just got sideways …..I believe the Mickey thompson e street R’s should be around 17 PSI?

I also have there subframe connectors from PTFB

I launch my car at 1500rpm, I'd start there and then raise or lower it 200rpm each way. Your car will tell you what it wants...

Need some Caltracs, what are your front shocks..with my car I stall up as high as I can which is only about 2500 or so before I push the tires and send it. You have to find the sweet spot..I've seen guys with FI have to tune out a lean spot at the track.

I am running the same Viking adjustable shocks up front…..I was gonna go with cal tracks but dave from PTFB told me the anti squat brackets did just as good of a job

My converter stalls at 4400 on the trans brake. But I don't use the trans brake because I red light every time if I do. I launch just off idle around 1100 RPM to eliminate a bog if I go right off of idle. Yeah I have a T-brake but I foot brake the car. If I launch off the brake at 4400 RPM my 60' times are not different than if I launch at 1100. So I do agree with what was said about launching below your stall point as you can take advantage of the torque multiplication of the convertor that way.

I tried to practice alittle last night on the street which is probably not a good comparison to the track because I wasnt aired down on the tires or even did any burn outs or anything…. But just off 1,500 rpm it spins like crazy and then off idle which for me is still around 1,100 is doesn’t spin but I can only part throttle it.

I would like to know for the street also as I do mess with some of my friends a bit….Im pretty sure flooring it even off idle on the street it’ll spin like crazy

You need some better tires. Doesn't matter how you launch it or how much power your car has if your tires and spinning like crazy even a SBC with a 283 with beat you in a race.

100% agree there…..But I am running mickey thompson E-street R’s on my 17 inch snowflakes….what else would you suggest running?

With a traction limited car, the brake probably doesn't help much. It can be used though to hold the car and keep the rear end from loading up like without the brake. (which also helps on the launch)

If running slicks it is great. (I've never used any kind of street tire that ever hooked)

With the break you can also hold the rpm steady even without watching the tach usually. Giving a more consistent launch and testing opportunity.

I've known a few fellers who have made a '2-step' type of setup for launching full throttle at low RPM and leave great.

:)

I have to "roll into" the throttle on my launches otherwise the tires will break free pretty bad, I have M/T drag radials & even on a good prepped track they will break free. I go to about half throttle or a little more very fast, but then roll into it to full throttle being ready to feather it a bit if i feel the tires wanting to break free. Its a balancing act, but for traction limited street/strip cars you gotta play with the throttle a little. I have zero traction aids on mine, just a homemade pinion snubber, might look into the anti squat or cal trac bars.

Also a 15" tire will do better than a bigger one because of more sidewall, thats why most late model cars with bigger factory wheels use 15" in the "drag pack" wheel set ups, 15" rear & 17" or whatever front to clear the bigger breaks. Ive heard the M/T pro bracket drag radials are the best hooking radial tire, but they are not DOT approved although I see guys running them on the street all the time, they do have a few small lines in them so that probably gets by the police if they see them.

I guess I just need to get a feel for exactly how to do that “roll into the part throttle” to go into full on my launches and the only way is to play with it and work on it

You have a lot of power going to the rear wheels so pretty hard to hook it up on the street. You didn't mention anything about your converter. There are things you can do to help with weight transfer like drag shocks and removing the front sway bar but it will not be practical for a street car. Moving the battery to the trunk will help a little taking weight off the front with a glass hood and/or front bumper. Adding ballast to the rear of the car will help too. What I would do is as soon as the tires start roasting shift it into 2nd gear it won't eliminate the spin but will slow it down quite a bit and the big cube motor won't know the difference between 1st and 2nd when the tires are spinning. In a drag race that first 60' will determine the winner most of the time. As stated above going to a 15" wheel/tire will help. In racing it's not the one thing it's a combination of a bunch of little things and for a street car it's a compromise. Weight transfer, a 15" tire with a soft sidewall taking weight off the front adding weight to the rear these things will make a difference. Putting a one inch spacer under the front springs will make a big difference too.

Following this thread with interest. I lost my lower right leg to sepsis 10years ago so I drive with a BK prosthetic leg. I made in to the track several times last year. First time I've been on the track in almost 50 years. I'm running in the high 12's but my reaction time and 60' are all over the place. Using the foot break I'm trying to get more consistency in my launch. Practicing on the street is just about useless due to tire spin. At the track I'm lucky to get in 3 or 4 runs during t'n't. Does anyone else have any issues were they have to modify their launch or driving technique? All comments welcome. Thanks!

The tranny brake would work great for that.
You can leave at any RPM you like. Stage with your mechanical brakes, pumping. Push brake when bulbs lit. Push tranny brake button. When when ready to leave release button. Then continue flooring it if not at full throttle when button released.


:)

You need to eliminate any factors that affect traction off the line and then go back and try. If you have traction issues with tire you run you need to upgrade. What tires do you use and what are the range of your 60' times? Do you have an A-body or F-body type suspension?