School me up quickly on drag racing please

Russ Noble

GT40s Supporter
Lifetime Supporter
I am doing a Classic race meeting at Ruapuna this Saturday. I have just seen there is a Drag meeting there on the Sunday. If my car comes through the Saturday OK, and the weather is OK, I am sorely tempted to to enter the drags.

I still know next to nothing about drag racing but have re-read this thread from a few years ago. http://www.gt40s.com/forum/worldwide-gt40-events/15505-gt40s-take-honours-shelby-festival-oz.html

I will be running the car in my standard race trim, ie treaded historic race rubber. With no line lock to hold the car, how do I get sufficient heat into the rear tyres before the run? Or can't I?

Any tips, particularly from kiwis familiar with the local conditions would be most appreciated.

Thanks in anticipation,

Russ
 
have you picked out a nice dress ?

Good luck. Be kind to your tranny ......... oh dear, that came out wrong......
 

Russ Noble

GT40s Supporter
Lifetime Supporter
Gee, thanks Tim!

With a heavy duty tranny chasing me up the track, I could forsee some pretty quick times....:burnout:
 

Keith

Moderator
Not sure that I would personally be too keen to drag the car at this time, before the wrinkles have been ironed. V hard on the drive train. Still, you (and Lim) really like working on it don't you Russ? :)
 

Russ Noble

GT40s Supporter
Lifetime Supporter
Every race start is a drag race and you don't get to call it quits after only 1320 feet! We've got the car, we might as well use it.....

On top of that there has been discussion on here, in days gone by, of times a GT40 can achieve. I'm just curious to find out mine! This is the last local drag meeting of the season and I only have a few circuit races left this season as well. So it is a little fortuitous that the opportunity has arisen now.
 
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Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
Hi Russ -

What the others said about the transaxle (can't hear it too many times now can you?)..
Also remember that the CV's and axles are taking quite a pounding as well..

I realize that your standing starts are a lot like drag racing - however - there is a difference. In a Road Race - the standing start is not a precision one that's measured over the distance of a quarter mile.
In Drag Racing - every hundredth of a second is precious, so you optimize your chances for not giving away any more time than absolutely necessary.

Prior to staging your car, you will be given an opportunity to warm your rear tires by doing a burn-out.

With the noted exception of Top Fuel / Alcohol classes which can do their burn-outs half-way up the track, the Sportsman classes are relegated to doing all their dirty-work "behind" the starting line and it is not only considered bad form to burn out across the line, but it may well get you ejected at some tracks.
You will generally get time to do one burn out and maybe a couple of "dry-hops" where you can actually test the tire's grip.

There are a couple of light beams that you will need to position your front tires in.
Pre-Staged and Staged. The idea here is for you to put your tires all the way through the pre-stage beams and just barely into the stage beams. If you go too deep or too shallow in the beams and your car rolls even a few millimeters, the beam will be complete and the timing starts. That's fine if the GREEN light is on. If, however, the car moves prior to the green light, you will be disqualified with a "RED" light... No sense in pounding on the car any more once you see that Red light as they typically stop the timing on your lane when that happens..

The rest below here I just went online and found at an NHRA site as I didn't want to type it all in manually (lazy this AM I reckon).. Drag racing can be a blast - I did it for many years in the sportsman ranks and all the way up to Top Fuel Dragster back in the early 70s.. I've since "come to my senses" and embraced the road courses..

Basics of Drag Racing
Drag racing made easy

A drag race is an acceleration contest, on a track, or dragstrip, that begins from a standing start between two vehicles over a measured distance. A drag racing event is a series of such two-vehicle, tournament-style eliminations. The losing racer in each contest is eliminated, and the winning racers progress until one remains.

These contests are started by means of an electronic device commonly called a Christmas Tree because of its multicolored starting lights. On each side of the Tree are seven lights: two small amber lights at the top of the fixture, followed in descending order by three larger LED lights, a green bulb, and a red bulb.

Two light beams cross the starting-line area and connect to trackside photocells, which are wired to the Christmas Tree and electronic timers in the control tower. When the front tires of a vehicle break the first light beam, called the pre-stage beam, the pre-stage light on the Christmas Tree indicates that the racer is approximately seven inches from the starting line.

When the racer rolls forward into the stage beam, the front tires are positioned exactly on the starting line and the stage bulb is lit on the Tree, which indicates that the vehicle is ready to race. When both vehicles are fully staged, the starter will activate the Tree, and each racer will focus on the three large amber lights on his or her side of the Tree.

Depending on the type of racing, all three large amber lights will flash simultaneously, followed four-tenths of a second later by the green light (called a Pro Tree), or the three bulbs will flash consecutively five-tenths of a second apart, followed five-tenths later by the green light (called a Sportsman, or full, Tree).

Two separate performances are monitored for each run: elapsed time and speed. Upon leaving the staging beams, each vehicle activates an elapsed-time clock, which is stopped when that vehicle reaches the finish line. The start-to-finish clocking is the vehicle's elapsed time (e.t.), which serves to measure performance. Speed is measured in a 66-foot "speed trap" that ends at the finish line. Each lane is timed independently.

The first vehicle across the finish line wins, unless, in applicable categories, it runs quicker than its dial-in or index (see glossary). A racer also may be disqualified for leaving the starting line too soon, leaving the lane boundary (either by crossing the centerline, touching the guardwall or guardrail, or striking a track fixture such as the photocells), failing to stage, or failing a post-run inspection (in NHRA class racing, vehicles usually are weighed and their fuel checked after each run, and a complete engine teardown is done after an event victory).

-------------------------------

Good luck and let us know how you make out!
 

Ian Anderson

Lifetime Supporter
Run low pressure on rear tyres for more mechanical grip
Up the pressure on front tyres - less rolling resistance

Beef up engine mounts (Especially left side that "streatches" under acceleration) - bust mine on old BF Goodrich tyres!

At Santa Pod they wet the track behind the start line for burnouts Gets the tyres spinning really quickly but without line lock you'll quickly move forward

Don't break it but fun for a laugh
About 14 seconds here by strictly road cars road tyres.

Ian
 
1- Line up
2- Rev engine to redline
3- Dump clutch (that's why God invented shocks springs in your
clutch plate)
4- Rev engine to redline
5- flat change every gear (Don't worry your valve springs will keep
the revs under control)
6- Pick up all your bits of metal and clean up the mess:lipsrsealed:
 

Russ Noble

GT40s Supporter
Lifetime Supporter
Thanks Randy for all that, particularly the comments of an old hand on the finesse of positioning the front wheels when staging.

Re all the comments about the trans, you know I think the 930 is bulletproof, it certainly doesn't get any preferential treatment. Feel free to say "I told you so!"

Flatchat, thanks. And a bench mark to aim for..... 11's...... optimistically..... hmmmm.....

Haha Dave, good one :thumbsup: I think I've got that side under control. I think there will only be one gearchange too, but at this stage I'm really into the unknown (for me)
 

Terry Oxandale

Skinny Man
IF (notice the big IF) the transaxle can take the shock, the hole-shot is the key to a win for comparable cars. I'd suggest a cheap set of rear wheels dedicated to drag slicks for this run, raising the ride height, and unhooking the front shocks and or sway bars to allow as much transfer of weight to the rear on the hole-shot. if you've got a sloppy set of springs and can soften the shocks on the rear, this will help the bite as well.
 
I say pull up to line, rev to limit, when light goes green dump clutch and speed shift. If you blow it up, repair and redo.
 

Howard Jones

Supporter
Set rear shocks to full stiff compression and full stiff rebound. Set front shocks to full soft rebound and full stiff compression. Set rear antiroll bar to full stiff. Front bar will do nothing in a straight line, leave alone.

Go up to 6 inches front ride height and down to 4 inchs rear ride height. Camber to as close to straight up as possible. Any change in camber (narrows contact patch) under compression is to be avoided. This is why IRS doesn't work drag racing.

Remove any extra weight, extra seat, run with 3 gals fuel each run max. Driverside fuel tank dry.

Any aero downforce to min downforce setting.

Borrow drag tires for rear of correct height for car. Don't worry to much about width. Hot drag slicks have a lot of grip and a 8 inch drag slick when nice and hot will have as much grip as a 12 inch street tire. Ask tire owner what to run for pressure.

Depending on gear ratios you might want to leave in 2nd and run through the traps in 4th. This is something you will know for yourself after one run.

Or........skip all this bullshit and just go for it once and see what you run, Have fun!!! Let us know how you do. Startline, out of car, video would be cool!!!!!
 

Russ Noble

GT40s Supporter
Lifetime Supporter
Some conflicting advice here about shock settings. I think I like Howards option.

Or........skip all this bullshit and just go for it once and see what you run, Have fun!!!!

The car seems pretty quick off the line in standard race trim, I'm just curious to put a number on it. This time next year, when I've sussed the lay of the land, I might do a max effort with drag slicks and screwing the suspension around.

Thanks for all the advice.

Any kiwi drag racers got any local info to add.....?
 
In my own experience of drag starts, which is pretty much what we do for sprints and hillclimbs, your terminal time will be very much determined upon the launch (how much wheelspin) and your terminal speed will be determined by how much power you have.

On Roy's GTD40, with the 347 stroker in it on an UN1 with Quaife ATB diff and 3.7? diff with straight cut 1st and longer 1st/2nd - IF I launched with anything more than 2500-2800rpm, the car would light up the rear slicks and basically hardly move. Road tyres or slicks, if you gave it loads it would just light them up.

Also - when driving another GTD40 on Webers with an organic clutch, a much higher rpm was required for the launch. This was about 4000rpm and below that the car would bog and falter. At about 4000rpm, it would spin just a little till but once the clutch was fully engaged, lifting very slightly on the throttle would be enough to regain the bite of the tyres and off you went..

Roys clutch was a more brutal metallic paddle type and not really slippable.

I'm surprised if you only need one shift - must have some very wide/long ratios. At Brighton quarter we needed 4th on occasions although if you can rev high enough you'll be ok.

Shift points are normally determined by your engine's torque characteristics. As soon as the torque starts to drop you really want to shift to remain in the max acceleration area of power delivery. (subj to ratios too)..

Another trick - Occasionally we used to launch in 2nd to save a shift. Worked well on slicks and was proven that saving time lost on the shift reduced overall ET. Data logging showed that the car speed dropped by 3-4mph during a change..
(can be a bit brutal on the ring-gear though and don't miss-select. I tried it in 4th by mistake and BANG - snapped a driveshaft - only time ever!)

Oh and if you can get a launch by max-revs and side-stepping clutch - Good luck! but I hope you've got 'deep pockets'....:shocked:

If you can get below 12s - you're quick. (mph 120+)
If you can get below 11.5s - you're very quick. (mph 130+)

Have fun!

ps - forgot to add - warming tyres will only really work if you get them to smoke, otherwise you are only really smoothing up the surface of the tyre. We spin them up in 1st by gently engaging clutch at low rpm then nailing throttle to hold 'near' max rpm for a couple of seconds. Be ready to hit brakes and also beware of rear slipping one way or other..
 
I seem to remember that your lower rear trailing arms are adjustable on the forward end for changing mounting height/pivot point.

If so you can raise them to try to intersect the cars CG, maximizing anti-squat.

Mostly though, just go have fun and rip it up!
 

Pete McCluskey.

Lifetime Supporter
From My limited experience, reaction time is very important. Try to anticipate the green light on the tree. To much anticipation and you red light of course.
If your wheels are spinning you are not going forward, if you have a low first gear it may be worth trying a start in second.
Good luck.
 

Pat Buckley

GT40s Supporter
Not to be negative, but if you get everything "right" you WILL break something expensive.

I would just do it for fun.

Hold the revs at about 4000 when the tree starts and feed the clutch in quickly and smoothly.

When the last yellow light goes on, leave.

The difference between doing it "right" and having fun won't be that great.

Of course this is your choice!
 
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