More Tracks R Going 1/8 How to gear a low HP Car??

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72DMag

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It sure seems like the sport of bracket racing is going more and more towards 1/8 mile. I'm sure there are various reasons such as insurance, longer shutdowns, quicker program etc....
How is everyone gearing there cars now?

I have what I consider a mild/low hp 360 with a 904 behind it in a 72 duster. With my fat butt in it, the car weighs around 3100 pounds. In the rear are 30" hoosiers and the engine makes about 500 hp at the flywheel at 6200 rpms.

Every calculator I see online says I need something like a 5.60 gear. To me that sure seems like alot!! Is everyone converting to such a short gear ratio for the 1/8 mile races? Or do you race with a 1/4 mile gear and try to hit 3rd gear before the finish line?

One of the online calculators I have used for reference is wallace racing:
upload_2021-7-19_12-3-9.png
 
The "problem" with 1/8 mile tracks is that in order to be competitive, you almost have to run a 4.10/4.30/4.56 gear or lower no matter what engine or power level you have.

Kinda kills the street/strip builds unless you're just running for fun.
 
I would suggest a 4.88 gear.
 
i run i/8 and the is about 3200#, 29.5 tall tire,5:13 gears, best time so far is a 6.78@ 101.9 and about 6200 rpm at the traps
 
I just leave my 1/4 mile gears in for 1/8th mile. It would be nice esp if you are a slower/lower hp car to pickup some and go faster in the 1/8th, but I don't see the gain in E.T. being that great. With increasing the gear you will have to be quicker to shift to 2nd and will launch harder so if your track isn't great or car can't hook on ice you will give up some consistency for a little bit of E.T. gain. As long as your shifting to Drive before the 594ft cone and it gives you a chance to have a look or 2 to play the stripe I'd let it be. If your having to shift between the 594 and 660 cones than you may want consider a gear change. I run a 4.56 and 30" tire. I'm shifting to drive before the 594 cone and have a chance to give a look and decide on what I'm going to do. It happens quick especially after running 1/4 mile but you get used to it.
 
@moparmarkk what stall converter do you have? I am running a 4200 stall and the car is footbrake. Are you getting that low of an et on a trans brake?
 
I've got a Dart Sport with a 360 weighing 3,540+ running mid-low 11's in the 1/4 and low 7's in the 1/8. Running 4.86 gears with 30"x9" radial slicks was already a lot, shifting just under 7000 and touching valve float in the lights. I tried 5.13 gears in the 1/8 and it didn't help. More gear can also overcome traction limits of the car/track.

There is always that "depends on your combo, your results may vary". Converter and spring pressures are likely factors but I can's say how much. I do know that it's easy to get into valve float without even realizing it. It starts before the car noses over on your shifts and/or at the finish. I also felt that too much gear would hurt longer stroke engines because they would blow through the usable torque range too quickly. Again, these are just my theories which may or may not be entirely sound.

I built my combo to the edge of the rules because I was trying to go as fast as possible within those class rules. For bracket racing, it best to stay on the conservative side. Consistency, predictability and reliability is what wins races, not necessarily being as fast as possible. Either way, you don't want to shift 2-3 "just" before the lights when you should be judging the finish line against your opponent. But I don't think that shifter 2-3 very early to max out your 1/8 mile rpm's is the best way to go either.
 
Depends on your build. I ran 4.30s to 5.13s my best 1/8 mile time was with the 4.30s. 600hp 440 with 5000 stall. 6.49 at 106.
 
moparmarkk said:
i have a 4200 also, but yes last run was off the trans brake.
Click to expand...

What gears are you currently running? I'm not a huge fan of big gears unless you're engine is built to turn a bunch of rpm's.

When I had the 340 in my Dart it ran mid 7.20's in the 1/8 and 11.60 in the 1/4, shifting at 6400 on 275 radials, 1.57 60' . It started out with 3.91's and I decided I needed more gear so I put 4.30's in it. The car picked up .04 in 60 and carried it through the 1/8. Not worth the money or time spent IMO.

It's currently running 4.10's with a 275, at 55mph it's turning 2900. Very easy for me to live with.
 
Old school way was, what is the 2-3 shift point and then rpm at the stripe ?
So let's say shift 2-3 at 6200 and cross the line as close as possible to that peak rpm or a little less say 5800 at the stripe.
What you don't want is to have the peak (as stated above) before reaching the stripe.
I hope it makes sense. Just a thought.
 
thanks for all the inputs. I have an 8 3/4 behind the car so swapping gears won't be as hard compared to a dana. I might go with the 5.13 just to see how the car reacts.

I kinda want to capitilize on all 3 shifts within the 1/8 mile. Last year and this year the local track has no 1/4 mile races for competition. :( Mark's car mentioned above sounds very similar to mine. I'd suspect with foot breaking I would see closer to 6.88 - 6.95 et in the 1/8. based on all the comments as long as the car doesn't have traction problems the shorter 5.13's should work better than a taller gear. Also sounds like this is a trial and error thing but I just really needed a good starting point. Thanks again for everyone sharing their input!!
 
when it hits third it just pulls, have 590 mopar cam old school ,at 101 center line ,the car is pulling like hell in third ,good luck and keep us posted
 
Darter6 said:
Old school way was, what is the 2-3 shift point and then rpm at the stripe ?
So let's say shift 2-3 at 6200 and cross the line as close as possible to that peak rpm or a little less say 5800 at the stripe.
What you don't want is to have the peak (as stated above) before reaching the stripe.
I hope it makes sense. Just a thought.
Click to expand...
This is what I was told and have always done good with. Basically I was told you want to finish at your shift point in high gear.
 
I run 433 spooled in a bullet proof 8 3/4 like so many have already replied I simply run the same ratio 1/4 or 1/8. That being said I am not really that serious and our track is 1/4. If we changed to 1/8 I guess I would rethink my position. I stay just north of 10 so as not to end up in a different class. Going below ten is a black hole for money and I ain’t got it. To a serious racer my Philosophy is blasphemy. I just like getting out there and throwing my junk down the track.
 
I, too, avoid the nine second threshold.
I have two tracks near my house, twenty miles in opposite directions, one 1/8, one 1/4. (I personally prefer the 1/8 track, but thats neither here nor there.)
My small block car, i started with 5.14s in a nine, because of 14x32 tires. It seemed a little much, so i changed to 4.71, and the car slowed down......nothing. I can run either track.
My big block car has had 4.56, 4.11, currently using 3.91s. It doesnt care what gear is in it. I also learned it runs just as fast shifted at 5900 as it does at 6400. I am in high gear by about 400 feet.
My new big block car is going out at first with 3.50s for the eighth, we will see how that works. 4.10s might be the first change.
I guess what i am trying to say, is..... i am not really impressed with success with very low gears.
 
I would even endeavor to go 5.33! with 30" or taller tires!

I ran 4:56 with 29" tires and ran out at as high as 105MPh. Stupid top end number and 7.56 ET or so with 383/509 purple. The 1/8th can be lots of fun!
 
As mentioned, they have to be geared to be in high gear and maybe a couple hundred RPM's before shift point. Sorry, I'm kicking concrete, but I just can't stand the movement of 1/4 out - 1/8 in.
 
1969383S said:
I would even endeavor to go 5.33! with 30" or taller tires!

I ran 4:56 with 29" tires and ran out at as high as 105MPh. Stupid top end number and 7.56 ET or so with 383/509 purple. The 1/8th can be lots of fun!
Click to expand...
My Dart runs 7.20 in the 1/8th... 11.50 in the 1/4 on purpose.. car is slowed down to run 11.50s / 7.20s. 3150 lb Dart 408 small block, 904, 4.30 gears going thru traps (1/4 ) at 6300. went from a 4.10 to a 4.30 gear.. no difference 60 fts. still 1.49-1.51 foot braking

33523EDD-4AB8-4A7F-878A-882C305C8AE0_1_201_a.jpeg
 
BVoelzke said:
My Dart runs 7.20 in the 1/8th... 11.50 in the 1/4 on purpose.. car is slowed down to run 11.50s / 7.20s. 3150 lb Dart 408 small block, 904, 4.30 gears going thru traps (1/4 ) at 6300. went from a 4.10 to a 4.30 gear.. no difference 60 fts. still 1.49-1.51 foot braking
Click to expand...

What MPH on the top end of an 1/8th? Always foot braked and was talking 1987.

Protrac Street radials.

With full exhaust and cast Iron!
 
Last edited:
I always thought running 1/8 mile on a quarter mile track was to keep cars under 150 mph.
No need for a chute.
 
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