A 9-10-11 range SLR is desirable.

When shooting for the best SLR would a 9 be consider your best SLR or do it even matter?

Need a little more info, like size of engine, weight of car, size of the rear tires.



Joe

As much as you can get and still hook. I run 10.53 SLR with 10.5Wx31 tire. Car has 54% on the nose. Mid 1.2x 60ft foot braking. it took awhile but it is pretty consistent.
Doug

I would agree with this but add "and not go on the back bumper "!

Really depends on weight and power. Power adder combos can and need to run lower SLR's to manage the car at the hit.

Manual or automatic?
(I suppose most are running torque converters but there are a few of us shift-lovers out there)

My new combo will have a SLR of 13.22:1... But it's a stick car.

IMO it will deped alot on the combo and intended purpose for sure. But the most you can hook up consistently for sure. FWIW the Vette is 11.3:1 and my Stratus 7.72:1. The former has been 1.13 60 and the latter 1.02, as pointed out is fairly combo dependent IMO

Many many variables. Cant single out a number, its whatever SLR the combo wants.

And if you are shoe polish racing sometimes less SLR is better.

My Dart with a Glide has a SLR 8.75 1.80 X 4.86

My old Duster has a SLR of 10.0 2.45 X 4.10

It matters a great deal. Hit the sweet spot and the rest of it becomes much easier (less difficult?).

Mine was 9.6 for what I was doing. Yours is probably different. Every combination is. Weight & bias, power, suspension, tire, track, what you are trying to accomplish, etc....

I had everything from 1.76 to 2.74 in mine with a couple of different rear ratios. A four link and good shocks will let you get more aggressive with it.

What are you using to calculate SLR ?

i always thought SLR was transmission low gear ratio times differential ring and pinion ratio.

Math
AKA, I change the low gear ratio and rear end ratio in my old NHRA legal M.W. 1963 415 HP Stocker, took out the 4.89 rear gear with the stock 2.45 727 low gear ratio = 11.98 SLR to a 4.56 rear gear and swapped the trans to a Mopar 2.77 low gear ratio which made SLR 12.63 ratio.
Those two changes made that car a lot quicker and faster
I was running that car in B/SA at that time and it had to weigh 3520 with me in it, NHRA had lower the HP factor on the 1963 low compression motors 405 HP due to them having a smaller set of carbs and a smaller camshaft than the 1964 M.W. low compression motors had
Test, test and test some more to learn and hopefully go faster and quicker

More factors besides low gear + axle, which is why some PG trans work well.
AT: add the stall ratio, stall speed, launch RPM (crankshaft inertial mass), and converter-flex plate stored inertial mass.
MT: add the launch RPM and clutch-flywheel-pressure plate stored inertial mass.

If the total is too high the car is not repeatable or violent on launch.

Torque multiplication. Which is why auto trans low gears will be ~1.80 to 2.70 and manual trans will be very high 2s and more commonly low to mid 3s.

SLR is a simple arithmetic calculation. Low gear times rear gear. A hundred other factors will determine what that sweet spot is for your situation.

The last 4 speed drag race SB 340 car I drove at the track was a 1970 Duster with a set of 5:57 rear gears with a 3.09 first gear NP833(17.21 SLR, let the clutch out at 7000 RPM and shift at 7000 RPM 3 times very quickly ), you were real busy the first 400 to 500 feet or so with that car

My GTS has a 2.66 1st gear and a 3.23 R&P in the diff. 235-60-14 tire.

Thoughts?

We changed the SLR in this car from 9.17 to 7.77 , literally no change in the ET . But now it barely picks the tires up

In a perfect world, you would take a car like yours and reduce the trans gear, and increase the rear gear. Experimentation like this would accelerate the car and help tighten the converter at the stripe. This would pick the car up on both ends as more rear gear doesnt work the converter so hard and allows it to not slip as much. Im sure you know this but just a good example for people to read. Once you get a good SLR that the car likes you play with it, you can keep the SLR but change the trans gear and rear gear. keep the slr the same and change the mechanical advantage at both ends of the track.

My opinion is your car might be faster with less SLR because wheelies are slower than wheels on the ground passes......BUT who am i to say that?>??? LOL

In the end its expensive and a lot of work, but thats how you go real fast

3.28 in trans 5.57 in Dana 18.27 SLR 9 X 29.5 tire Shift in the air.

Cab, you could give George Carlin a run for his money.

Op, let me clarify, auto or manual? What is your current axle and low gear ratio.

As Poly mentions, with an auto STR greatly affects SLR.

I know that car Fast then and faster when I saw it last

500 cu " 3350 race weight , 727 stock tranny gears,10.5 29 tire on a 12
' wheel.

Wallace cal.

^^^ Right here is what i'm trying to get rid of,i trun down the two step and it's doesn't get as high but my 60's have went from a best of 1.27 to 1.31.
Also i should have mention that i also went from 4.56 to a 4.10

I have a stock geared 727 in my cuda and I use 295 drag radials. Motor makes somewhere around 850 hp, plus 300 hp of nitrous.
With a 4.10 rear gear, the SLR was 10.0 and it was uncontrollable on nitrous. I rarely ever got it to hook, but when it did, it just did wheelstands. I had a couple of "good" passes where it went fast, but the vast majority of runs were aborted.
I swapped in a 3.54 gear for an 8.67 SLR and it made a HUGE difference. It has hooked almost every pass since. The only time it didn't hook, I had the front shocks set too loose.

The drop in SLR hasn't seemed to affect the ET much so far...on the nitrous anyway. I'm still tuning this thing, so getting it to hook and repeat has been priority.
With the tight 4k nitrous converter and 3.54s it still ran 9.69 at almost 142 mph on motor only, super sluggish 1.43 sixty foot.
Best NA pass w/ loose 5k converter and 4.10s was 9.54 at 140.4 mph, 1.32 sixty foot. The car would usually hook anywhere the track was at least halfway decent w/ the NA setup.
At my car's weight (over 3800 lbs), I really need a different trans.

COUGH....Glide with 1.58.....COUGH

LOL, I know, I know! It's just a toy though and I'm not spending that kind of money on it. Just gonna see what I can do w/ what I have.

Who's making a transbrake for Torqueflites that will use second gear?

CRT does.

I think you need to work on the shock settings(maybe valving)and concentrate on the wheelspeed side of things more than worrying about the SLR. . Here is a video of 11.3:1 SLR that builds wheelspeed right now, and what most here would consider to muchbut if you can control wheelspeed it will always be the fast way down the track with a bias slick. We run the same tire you do a 29.5x10.5, we have been 1.13 60' with no wheelie at all, but if I wanted to i can just about flip the car over with a twist of a couple screws. If we are talking radial tires its a different animal but I assume when you list your tire size its a bias tire. And in that case wheelspeed is the key...Oh yeah excuse the make of the car its what we race these days

Guess i could ad the Savoy has an SLR of 10.4:1 and seems to work ok. Dont get hung up on an "ideal" SLR number as it is VERY combination dependent. Savoy ran a string of 1.33 60's a couple weeks ago at 7000' plus DA ar 3530lbs in Vegas pulling 12 degrees ramped in over 1.25 since we cant get new tires, well the ones we want anyway.

Very true.

Being over center, one way or the other a little bit, can be tuned around - shocks, four link, nitrous or timing timer, etc - but being way off is not going to work.

My car was a miserable turd with a 1.76 and a 2.45 low gear, but for different reasons.

With a 1.98, it would 60' the same as the 2.45. The difference was it would do it every time, everywhere, and not whip the tire every third run.

Thanks Al...i made the switch from a stock front end to a tubular front /coil overs i have the single adjustable fronts shocks , i had to have the shocks re-valve cause of weight transfer issues (is there a thin line between valving?) By the way the shocks are the Afco's if it matters. Some here say that they pull timing and ramp it back in that's a ideal to but that would require a ignition box change for me. My SLR right now is 10.05 and me thinking 9 something would be a better SLR but i see some here have SLR in the 7.

The trap rpm is as high I want with what parts are in the motor. The front shocks (Afco doubles) are running full tight. They have been tightened up once. Going to see if they can make them tighter yet. We aren't allowed any timing ramps in N/SS.
Doug

We pull zero timing, in fact we ADD timing in first and second gear in the Vette. I did in the Savoy because the tires are 7 years old and track temp was 155, and its a bracket car which is a different animal.I used those two examples to show why dont get hung up on a "magic" SLR number, there is not one every car is unique. Wanna really throw a wrench in the works our dragster is 7.38:1 and has been 1.03 60'(dont pull timing there even with a torque monster of an engine, good shocks control the housing and tire)

IMO ramping timing in on an NA deal is a crutch at best to cover up a poor working chassis or chassis issue. Make the chassis work and leave the timing alone, unless you have some huge torque monster on an engine like some we run with in NA 10.5, they go up to 700"+ or maybe a leaf spring car as I don't have much experience there so wont comment. NA engines generally don't recover very well when you pull timing in them and in some cases can be a significant amount of power lost. if and when I can get new tires on the tank I don't plan to be pulling timing for sure.

We had AFCO's on the Vette for a very long time up front. But the car basically has no front end travel, at most its 1/2" of travel. The travel simply is not needed in this case we let the ladder bars do the work. The single biggest gain we have seen was going to a shock built specifically for this car and its intended purpose. Our shock guy is Adam Drzayich and the shocks are custom Penskes. FWIW the Vette is 100% factory Chebbie stuff, sans the shocks obviously. Stock A Arms, stock steering box, stock steering with the addition of a steering stabilizer for the bumpsteer the stock front gets us.

in the end it is a give and take. The only way to find what works for you is try different stuff. IMO learn to make the car work with full timing. Ultimately adding it in low and second gear will make the car faster. It will help burn the excess fuel off from being on the chip at the hit and will benefit in second gear from the multiplication of the gear set. Get it back to base in high gear. But if you have a box that cannot make that happen for sure quit pulling timing. Learn to make the car work with all the power. Video is your friend for sure as well as info, Not sure if you have any data logging capability but alot can be learned there.

Al , adding timing instead of pulling more is how a lot of nitrous cars are picking up the last few years now. and yes Data logging is key to making smart choices. The data logger pays for itself in Converter , Gears, and trips to the track, wear and tear on the car. It cost a lot to make a lot of passes, Data logger is the cheaper route in the long run.
I recently helped some guys go faster than they have been with a progressive VS no progressive and a tiny bit more timing while progressing....but thats another topic LOL

Safe to assume you have a Glide in the 64?

Joels on Joy Proflite...FWIW the Vette has an A1 Proflite in it.

How you getting such a low numerical SLR.

If money wasn’t an issue , I would have a 1.80/4.56 glide tomorrow. I bracket race only, and like to win. I also abhor the sub 10.00, over 130 s.f.i. mandates. Before I get roasted, ALL my safety equipment is ALWAYS in accordance with all NHRA rules, I just don’t want to wear more. As good as the car is with a 2.45 torqueflite, and as much as I love them, a glide combo would be even tighter. Different strokes and different rules for all racers, make any combo good, or null and void. I like them all, just don’t want to race em’

2.28 first gear 4.56 rear gear=10.40, not exactly that NUMERICALLY low as most bracket cars are much lower numerically. Like our dragster being 7.38 or the Stratus being 7.72.

Low to me since I assume (I know, don’t assume) you had the standard 2.45 low gear in the 727.

So that meant to me either a 4.24 axle with 2.45 low or some other 1st gear ratio and axle combo.

Thanks for the info.

Al , does the savoy have double adjustable on the front or all the way around if any?
I see you are able to pull timing out so i assume that you use a digital 7 or better box .
I guess my SLR is consider a decent one at 10.05

Yes it has double adjustable front and rear, Strange to be exact and so far seem to work well. It has a Grid in it, we will try to take the timing ramp out with these tires but when new ones go on it will be gone for sure and we will be adding timing at the hit rather than removing it. Was just worried the 7 year old tires and hot track might be a problem. Neither was an issue but we were bracket racing and just left it alone.

Like I say there is no magic bullet number. Some cars will gain nothing switching dramatically in SLR, others will react to small changes. Suspension style and efficiency IMO has a lot to do with that.

Transman, I am sure you are aware there are a myriad of gear ratios available for a torqueflite. We run a 2.19 and 2.14 first in the Vette, in conjunction with rear gear and converter to get it to respond to weather conditions to find the "sweet spot" for this combo. I was just using it as an example of how one can make a steeper SLR work. Heck most folks here would faint at where we like the converter to stall at, 95-9600

Tell me where you get your valve springs so I can buy stock in the company

PAC I know a guy. You probably dont wanna know what kind of RPM it sees at the stripe then Its just a small block after all

What kind of “converter out” fluid temp you seeing at the stripe? If you don’t mind sharing.