1/8 Mile Gearing ?

For door cars with SBC that are racing strictly 1/8 mile, what RPM are you crossing the finish line at? Please list your trans first gear, diff gear, tire size and engine cu in with 1/8 finish line RPM. If you post the ET and MPH, include 60’ time and the car weight with driver. Thanks!

I like to shift at about 200 RPM over peak power and come across finish line at same RPM.

Do you know what RPM peak power is on the motor?

Currently, 14:1 383, AFR 220's as cast, 850 Holley, .570/.590 Comp 4/7 swap flat tappet.
TH-400 w/2.10/1.40 low gear set, 5800 flash spragless converter, 4.33 rear, 29.5x10.5 M/T PBR's
4200 2-step, 6400-6500 shift, cross finish @ 6400+ and 100-102 MPH
1.40 60', high 6.50's to low 6.70's dependent on atmosphere. 3250# w/driver

Going back to 4.56's which will put it back to 1.35-1.36 60' times.
Best of 6.48 @ 103 / 10.36 @ 126 crossing 1/4 at about 7200, -400 DA

4.56, 1.80, 32" tire, 406 alky carb, 3050 lbs launch 4000, 1.38-1.39 60',flash 6100-6150, shifts at 6600, across 1/8th 6200-6300, depends on weather a bit or headwind. There are some occasions it seems to go from 6200-4800 several times just before the finish line though??? Seems to happen in eliminations.

Jok

This message has been edited. Last edited by: Toad1,

370ci, PG, 180 low, 4.88, 29.5x10.5 PBR's

Flash to 6200
Shift at 7000
Crosses at 6600

Tried to run 1/4 but it hit the high side limiter at 7800 at 9.01 seconds.

quote:

I like to shift at about 200 RPM over peak power and come across finish line at same RPM. Do you know what RPM peak power is on the motor?

After a recent SLR change, flashes 6250, shift completes @ 7050 and 1/8 finish line 7200

Just wondering.
1/8 vs 1/4 gearing is something I never got my head around.
1: Why would it matter to a bracket racer?
2: If you go 2 hundredths quicker in the 1/8 is your life forever changed for the better?
3: If you get your best 60 and 330 with X gear, why change?
4: Will your track be consistent enough to switch from say, a 4:56 to a 4:88?

I'm a bracket racer & primarily race 1/4 mile but also race 1/8th mile. I have a set rpm range I'm looking to keep the engine within. My current SBC combo was shifting at 6,950 & going thru the traps around 7,200. Depending on how I was ripping the throttle or how I got rid of ET earlier in the run.

Anyway, I made a gear change in the off season that will hopefully get me where I want to be for the upcoming season. I changed the rear gear from 3.89 to a 3.55. That will knock some rpm out of it, but will raise my mph. Not good, I was cutting it too close with running 149.90 ripping the throttle on one run.

I also wanted to have the converter loosen up for this year. After talking with Kevin at Hughes, he wanted me to hold off due to the gear change. He thought I would pick-up 3 - 4 hundred rpm in stall. I was flashing to about 5,550 depending on weather. I still don't think the additional stall will be enough. I want to have around 6,200 - 6,400 rpm flash. With a tighter shift drop than 1,000 rpm I have now.

Hope to find out with the new changes & engine upgrades soon. Our season starts end of Jan.

2BKING

All of the bracket racing in Texas is 1/8 mile yet I still gear my cars for the 1/4 mile.

The key is the right converter and you will not lose much if any ET while being easier on parts.

May sound strange but a loose converter will usually hook up better. Yes it allows the motor to get up in peak power band quicker but it also lets the car get a little further down track and car momentum up before it reaches stall.
Quite a difference between say a 3500 stall that is in full stall 3 feet off starting line and 6200 stall that is not in full stall until 10 feet off the line. The car is going much faster before it goes into full stall and that will help you hook up in addition to faster ET's.

Still really to answer your question what GEAR or STALL for that matter you really need to know peak horsepower and torque at what RPM. Best way to do that is on a Dyno or lots of track testing and changing gears and converters.

Certainly hate to answer your question with another question and no answer but no way we can tell you what you need if you do not know what it has. With that said one of best in the business is Kevin Klienweber at Hughes converters. If you give him good information on your combination he can get you perfect converter and tell you perfect gear.

I know a few of us are straying away from the OP of 1/8 Mile Gearing. While gearing is important to help to keep you in your rpm range. IMO, the converter is more important than gearing. Don't get me wrong, they need to work together.

I like to study from the best & Luke Bogacki is one of them, along with Justin Lamb. I'm lucky enough to race with/against Justin pretty often & occasionally Luke. You only get better by racing against better racers & applying the lessons learned.

Anyway, in the video Luke primarily talks about converter looseness but to me there's one key word he used: efficiency! I know what I take away from word efficiency as it applies to gearing & stall/shift rpm drop. You also have to apply efficiency in other areas of your program also.

https://www.facebook.com/ThisI...deos/781196690853290

2BKING

With DC sbc, was curious what others finish line rpm results were if set up for only 1/8 mile. The response shows lower rpm for 1/8 finish line and some still able to run 1/4.

I stopped 1/4 ET racing in 2017 but was still geared for it until 2021 when I switched to only 1/8 gearing. A recent planetary change has me looking at possibly switching the rear gear now. My present SLR is not set for fastest/ best 60’, nor do I want it to be. I have used the same engine combination since 2015.

Being the faster competitor can be an advantage for first red light. I believe the faster car is less affected by wind.

This is apples to oranges but we race the heads up car at both 1/8 and 1/4 mile events. While the 1/8 mile events are mainly used for testing we don't change anything in the rear or trans gearing to run 1/8. While it may hurt us a little I don't think its killing it a lot. We can go 1.08 60' with an NA SB and we have three gears which IMO is big help here. FWIW RPM wise we go through the 1/8 on the converter, just having shifted into third gear 100ish feet before the 660 we are going 9500ish. 1/4 mile runs we go through at 10-10200. For us we would likely look at trans gear ratios as rear gear if it becomes a dedicated 1/8 mile car.

quote:

Originally posted by Al Alguire:
This is apples to oranges but we race the heads up car at both 1/8 and 1/4 mile events. While the 1/8 mile events are mainly used for testing we don't change anything in the rear or trans gearing to run 1/8. While it may hurt us a little I don't think its killing it a lot. We can go 1.08 60' with an NA SB and we have three gears which IMO is big help here. FWIW RPM wise we go through the 1/8 on the converter, just having shifted into third gear 100ish feet before the 660 we are going 9500ish. 1/4 mile runs we go through at 10-10200. For us we would likely look at trans gear ratios as rear gear if it becomes a dedicated 1/8 mile car.

Is this SB2? What is the engine size and car weight? List more details of what this is as I don't follow heads up racing.

Its a 400" Sb with Little Chief heads. ProFlite with a drop out 12 bolt in back, weighs 2750ish pounds deepening on what we need to make it work. It was an NMCA NA10.5 car which this coming year will be a new organization called Small Tire Pro Stock. Can find them on Facebook if interest4ed. Same rules as NMCA just a new name and venues.

quote:

Originally posted by Al Alguire: ProFlite with a drop out 12 bolt in back,

What ProFlite planets and diff gear?

Firs gear depends on which trans is in it either a -1, 2.16 first or the F-8, with a 2.18. Rear gear is from 5.00 to 5.28. FWIW we havea bolt together billet aluminum converter and a few stators.