Another Question On Gearing

Old 06-21-2007, 12:02 PM
  #1  
raz1056
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Default Another Question On Gearing

I'm running a 500 ci bbc with a glide in a 2650# Camaro, 14x32 tire with 4.11 gears. It runs 5.80/9.20 leaving easy and shifting at 6800, 1/4 mile rpm is around 6700. I want to make a gear change to pick up my 1/8 mile times because I run more 1/8 mile but don't want to gear it to where I can't run 1/4 from time to time. I'm thinking of a 4.56 but my friend is saying with that tall of tire I should go with a 4.88. The motor is still pulling hard at 7200 that's where te shift point was set when I purchased the car but it dosen't run any faster shifting higher. Just wondering how much the gear change might effect the ET's
Thanks in advance.
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Old 06-21-2007, 12:41 PM
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sp2816
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Since you are wanting to run some 1/4 mile and you want to keep the rpm's around 7200, I would have to say to go with the 4.56 instead of the 4.86's.

My car weighs 2650 with me and it has run a best of [email protected] and a best 1/8 of 5.69. It has 4.56 gears and 16x33 Goodyears and a BBC. I shift it at 7400 and go through the lights at about 7300-7400 at the 152mph. I run an 1150 dominator.

The second car is a 1967 Camaro (2450lbs) with a SBC. It has run a best 1/8 mile of 5.75, which would have run about 9.05 if they had been running 1/4 mile that night. So far, it has run a 1/4 mile best of [email protected] a few weeks ago. It has the 4.56 gears and 14x32 Goodyears. He shifts it at 7400 and it went through the lights at about 7300-7400 at the 148mph. He has the Holley 950HP.

Hope this helps some,

Bill M
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Old 06-21-2007, 01:13 PM
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raz1056
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Great Thanks that tells me what I need to know!
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Old 06-21-2007, 09:49 PM
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Wow, that info makes me feel like my 568 gear in my 2400pound camaro is a bit much.( bought the car rolling) I was shooting for 550's in the 1/8 at a local track that is just a little short, most cars run about 2 tenths quicker there than at a full 1/8 track.
The motor I'm building is a 13 to 1 comp 496 bbc w/ 722 lift, 316 duration lunati solid roller, merlin heads, 1050 dominator, glide and 5500 stall and the rearend is a dana 60 w/ 568 gears and 10.5w x33 slicks.
What do y'all think?
I will only be racing the 1/8 no 1/4 tracks around here. Do I need to change the gear to like a 513 or 488? or should I try it like it is and see?
I currently driving another car for someone with almost the identical motor, but its a full bodied 71 nova which is pretty heavy I would guess 3800#. he runs a 538 gear but has the shorter 29 inch tire and we are running thru the traps at about 7000 with 6'00s e.t respectivley.
Thx Charles
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Old 06-21-2007, 10:26 PM
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sp2816
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It looks like you would be running at about 124-125mph in the 1/8 when running the 5.50's. Sometimes the ET can be quicker with less MPH, but we will figure it being even for now. When I ran yours through the calculations, it showed at 7200rpms (no slippage) with the 33" tall tires and the 5.68 gear that you would be running at about 124.5mph. Depending on converters, a rule of thumb is to figure 300 rpms for slippage, so that would put you around 7500 through the lights, which I would think would be about ideal.

Since you said that the track is a little shorter than the full 1/8, you will probably only be at about 122mph and be at less rpms.

I would say that this would be about the correct gear for running the short track. With the light car and steep gear, it should give you some 1.1x's 60ft times, which will be a rush. My best was a 1.23 which felt awsome.

Good luck and let us know what it runs,
BillM
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Old 06-22-2007, 05:51 AM
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studeracer
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what information do you need to select gear ratio ? can you help me on my selection?
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Old 06-22-2007, 06:14 AM
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sp2816
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The things necessary are the rear tire size (assuming rear wheel drive), transmission (overdrive? torque converter?), max engine rpm, and max mph expected (1/8 mile, 1/4 mile, or ?).

A page with some of the calculators is:
http://www.wallaceracing.com/Calculators.htm
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Old 06-22-2007, 08:24 PM
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cepx111
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Thx sp2816,
I appreciate you do the calculations , I will stick with the gear I have.
I cant frigging wait to get this car together , unfortunatley my wallet and bank account arent as enthusiastic as I am.
I have the motor about done now, but still have no tranny or converter yet, paying for everything with cash sucks but its nice not having credit cards bills though.
Hey one more question if you dont mind.
What first gear ratio is best for a glide the 1.82 or the 1.76?
Thx again, Charles
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Old 06-22-2007, 09:42 PM
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sp2816
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cepx111 wrote:
What first gear ratio is best for a glide the 1.82 or the 1.76?
Thx again, Charles
The stock 1.82 gearset is very light weight and I have broken them with 9.90 cars. The 1.76 stock gearset is pretty stout and I have run 8.99 with them, but I now have a 1.80 straight cut gearset. I would recommend that you run the 1.76 for the strength and affordability.

Bill M
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