starting line gear ratio?

older racer · 08-12-2021, 11:23 PM

watched vid on 289 mustang, ss/L 20.398 start ratio

Rory McNeil · 08-13-2021, 08:00 AM

What is the intended combination, and combination? With my old M/S 85 5.0 Mustang, I ran a 3.19 low gear in the Jerico, and with 4.88 gears, that made for a 15.56 SLR, and with 5.13, a 16.36 SLR. That was with 29-29 1/2" tall tires. I would have liked to have tried a bit lower rear axle ratio, but for the Ford 8.8, there was nothing between 5.13 and 5.7. Unless it is a really lightweight car with lots of power, and borderline ability to hook up, I can`t imagine a 11.25 SLR would be anywhere close to ideal. My SB Ford 4 speed G Force bracket car also has a 16.36 SLR,albeit with 31" tall tires, plus an additional 25 MPH, but looking to add a bit more rear gear ratio, or shorter tires to give another 1 or 2 hundred RPM at the 1/4 mile finish line. Same with my old hot rod type cruiser, currently has a 2.78 low Toploader with 3.50 rear and 28" tall tires, a 9.73 SLR, and I am barely hitting 4th gear at the finish line. Plus at over 4000 pounds, the organic street style clutch isn`t very happy. Hopefully the 4.33 gears (12.03 SLR) will help performance, and clutch life, at the track. And if I was to decide to switch to a modern overdrive 5 speed, I would be looking for a low gear in the 2.8 to 3.1 range.

Stan Weiss · 08-13-2021, 09:24 AM

This is what my software suggests.

Stan

Mike Pearson · 08-13-2021, 10:31 AM

Back when I ran a stick in my car the SLR was about 19 to 1. With the same engine combo and a glide the SLR is 12 to 1. The engine is much better now and the car is about a second faster than it was with the stick.

Bench Racer · 08-15-2021, 10:06 AM

For what it’s worth, my brother ran a 58 Chevy wagon back in the 80’s in IHRA Super Stock (basically a econo modified engine). It was a 283 that weighed 3839 and ran a turbo 350 with a 6:83 Dana and 29 and 30 inch tires for the 1/8 and 1/4. The torque converter was pretty a good piece back then but could likely have been ran on the street now. The car held the IHRA class record before he bought it and did until he sold it. I don’t remember any 60’ numbers but the car got quicker after putting In a 2:75 low gear. Don Jackson

Bernhard · 08-15-2021, 12:51 PM

How does engine cubic inch and an engine's ability to RPM factor into the SLR?

Mike Rietow · 08-15-2021, 11:23 PM

I caught a little NHRA Stock qualifying highlights today from Topeka. I don't know much about this class really as far how elaborate the engines are allowed to be, or how much they have to weigh, but this car runs about like my n/a 23 degree sbc on 10" tire 69Nova.

What SLR do these class cars typically run? What transmission and how many rpm's do they typically cross? It was a current model Camaro, is it limited to an LS? I think the announcer said 409cid. Just curious, run pretty good seemed like.

08-12-2021, 11:23 PM	#1
older racer Member Join Date: Aug 2010 Posts: 212 Likes: 13 Liked 68 Times in 26 Posts	Re: starting line gear ratio? watched vid on 289 mustang, ss/L 20.398 start ratio

08-13-2021, 08:00 AM	#2
Rory McNeil VIP Member Join Date: Jun 2007 Location: from Vancouver BC Canada, now in Nova Scotia Posts: 1,311 Likes: 317 Liked 1,104 Times in 302 Posts	Re: starting line gear ratio? What is the intended combination, and combination? With my old M/S 85 5.0 Mustang, I ran a 3.19 low gear in the Jerico, and with 4.88 gears, that made for a 15.56 SLR, and with 5.13, a 16.36 SLR. That was with 29-29 1/2" tall tires. I would have liked to have tried a bit lower rear axle ratio, but for the Ford 8.8, there was nothing between 5.13 and 5.7. Unless it is a really lightweight car with lots of power, and borderline ability to hook up, I can`t imagine a 11.25 SLR would be anywhere close to ideal. My SB Ford 4 speed G Force bracket car also has a 16.36 SLR,albeit with 31" tall tires, plus an additional 25 MPH, but looking to add a bit more rear gear ratio, or shorter tires to give another 1 or 2 hundred RPM at the 1/4 mile finish line. Same with my old hot rod type cruiser, currently has a 2.78 low Toploader with 3.50 rear and 28" tall tires, a 9.73 SLR, and I am barely hitting 4th gear at the finish line. Plus at over 4000 pounds, the organic street style clutch isn`t very happy. Hopefully the 4.33 gears (12.03 SLR) will help performance, and clutch life, at the track. And if I was to decide to switch to a modern overdrive 5 speed, I would be looking for a low gear in the 2.8 to 3.1 range. __________________ NHRA 6390 STK M/S 85 Mustang

08-13-2021, 09:24 AM	#3
Stan Weiss Senior Member Join Date: Apr 2020 Location: Phila, PA Posts: 794 Likes: 0 Liked 734 Times in 385 Posts	Re: starting line gear ratio? This is what my software suggests. Stan Attached Thumbnails

08-13-2021, 10:31 AM	#4
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,450 Likes: 615 Liked 1,931 Times in 580 Posts	Re: starting line gear ratio? Back when I ran a stick in my car the SLR was about 19 to 1. With the same engine combo and a glide the SLR is 12 to 1. The engine is much better now and the car is about a second faster than it was with the stick. __________________ Mike Pearson 2485 SS

08-15-2021, 10:06 AM	#5
Bench Racer Member Join Date: May 2002 Location: Green Creek (Tryon) North Carolina Posts: 331 Likes: 69 Liked 99 Times in 21 Posts	Re: starting line gear ratio? For what it’s worth, my brother ran a 58 Chevy wagon back in the 80’s in IHRA Super Stock (basically a econo modified engine). It was a 283 that weighed 3839 and ran a turbo 350 with a 6:83 Dana and 29 and 30 inch tires for the 1/8 and 1/4. The torque converter was pretty a good piece back then but could likely have been ran on the street now. The car held the IHRA class record before he bought it and did until he sold it. I don’t remember any 60’ numbers but the car got quicker after putting In a 2:75 low gear. Don Jackson

08-15-2021, 12:51 PM	#6
Bernhard Junior Member Join Date: Jan 2012 Posts: 30 Likes: 0 Liked 1 Time in 1 Post	Re: starting line gear ratio? How does engine cubic inch and an engine's ability to RPM factor into the SLR?

08-15-2021, 11:23 PM	#7
Mike Rietow Junior Member Join Date: Apr 2017 Posts: 93 Likes: 19 Liked 30 Times in 16 Posts	Re: starting line gear ratio? I caught a little NHRA Stock qualifying highlights today from Topeka. I don't know much about this class really as far how elaborate the engines are allowed to be, or how much they have to weigh, but this car runs about like my n/a 23 degree sbc on 10" tire 69Nova. What SLR do these class cars typically run? What transmission and how many rpm's do they typically cross? It was a current model Camaro, is it limited to an LS? I think the announcer said 409cid. Just curious, run pretty good seemed like. __________________ 7x S/Pro 'Sunshine" http://ottm.store https://youtu.be/I8QWEaqeFRw Last edited by Mike Rietow; 08-15-2021 at 11:31 PM.