Author Topic: 1/8th mile gears  (Read 6226 times)

Offline retroboy

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1/8th mile gears
« on: April 16, 2016, 08:26:44 PM »
Howdy.
Following from my post about gears and tyres what are you guys running on the 1/8 mile? A Mate has a set of 5.0 gears gathering dust and I'm thinking 6500 RPM through the top end would see me right.  I had a look at a couple of online calculators but don't really think they are very accurate.  Here's my story :-  I have a 366 Chrysler basic engine - standard heads. Should make 400 - 420 HP 400 Ft/Lbs with a carb. My TF904 has a 2.45 1st gear. Currently 4.3 diff and 31" tyre. I lashed out on an 8" converter that has 5200 stall but because of Torqueflight transmissions willingness to literally explode I'm not using a trans brake and the the car isn't heavy enough to get the converter to flash up properly.  Most of the basic 1/8th mile cars in my area are using 1/4 mile gears so I figure the only way I can get around 'em from the back of the qualifying order is to beat 'em in the first half of the track hence the change to a lower gear set. Any thoughs and no I don't see a powerglide in my future. What Tyres Gears Rpm are you guys running in your little guy 1/8th mile combos.
Cheers

Offline wideopen231

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Re: 1/8th mile gears
« Reply #1 on: April 17, 2016, 05:51:42 AM »
Since you don't agree with calculators this may not be worth anything. My drag simulator and Wallace both say that 4.80 is max gear for 6500 rpm setup. Not sure why  no PG comment.IMO the weight savings alone would help not to mention a lot of rotating mass removed.For  400 or so hp motor a PG is fAIRLY CHEAP BUILD.You could use a 1.76 gear with mostly factory stuff and few upgrades.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline retroboy

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Re: 1/8th mile gears
« Reply #2 on: April 17, 2016, 06:16:25 AM »
Hi Wideopen. I went from a clutch 904 to a PG 35 years ago and the PG was a dull rid like my first wife. I'll be honest this whole gears and converter thing has me bluffed. The calculators seem to give high expectations ?
Cheers

Offline dusterdave173

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Re: 1/8th mile gears
« Reply #3 on: April 17, 2016, 07:40:52 AM »
I raced a Torqueflite for over 25 years  here is the scoop
Never--Ever do a burnout in first gear PERIOD! Always start in second and go to 3rd as soon as tire speed is up and you will never hurt a TF.
When you do a burnout in first and the tires bite--the over running clutch or sprag comes to an instant stop
and as it is pressed into the case on a 727 it is easily damaged so that the next run it fails --then there is no control so it will spin the guts the engine RPM x the rear gear ratio usually over 20K RPM range and Kaboom!!  very simple to avoid
904 has a stronger deal on the sprag and usually is much tougher to hurt than a 727
You are correct in that there are not very good transbrakes for the TF--when the button is pressed it does not set instantly like a glide and when they do they change over the evening as fluid temp increases so not useful for winning a bracket race but should do OK for what you want
also 904 converter hubs are easy to crack--you can replace with thicker hub and machine down the support--easy to do or just replace the cracked hub every now and then--even when cracked they rarely fail there
Rick Allison at A&A transmission in Indiana is the DADDY of TF parts makers and TF knowledge--most builders get parts from Rick--he is the worlds BEST TF guru  Not cheap but simply the best parts and tech available
Wallace Racing Calculators--online-- just google are the very best out there--we use them every single day
I have always had a fascination with fast cars at the expense of more normal character development

Offline George

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Re: 1/8th mile gears
« Reply #4 on: April 17, 2016, 07:44:52 AM »
We have run very well with the PG (1.80). A 600+ hp SBC, injected on methanol, 4.88., 12X31 tires @ 1500 pounds went low 5.0s on 1/8 mile. I suggest you put the 5.0 gear in and go try it.

Offline masracingtd1167

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Re: 1/8th mile gears
« Reply #5 on: April 17, 2016, 08:09:51 AM »
One thing to add about a TF trans . Never throw it into neutral at the end of a run unless the valve body has a clean neutral . That can make them blow up !

Offline masracingtd1167

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Re: 1/8th mile gears
« Reply #6 on: April 17, 2016, 09:29:23 AM »
If it was my car I would try something like a 29x 10 inch tire and leave the gear alone . with that low first gear you are going to have a tough time getting the car to leave . The weight of the car has nothing to do with stall speed !   Bill

Offline retroboy

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Re: 1/8th mile gears
« Reply #7 on: April 18, 2016, 03:18:43 AM »
Howdy Thanks for the various opinions. I went and looked at Wallace Racing .. man they have a lot on there. In the formulas are they looking at flywheel or rear wheel HP ?
Cheers

Offline jeff/21

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Re: 1/8th mile gears
« Reply #8 on: April 18, 2016, 04:58:49 PM »
how wide are your 31s , do you stage at idle or a higher rpm? i would try the 5.00 gears, even with 29 x 10 which would like because of your hp i would run more gear

Offline Scott Krieger

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Re: 1/8th mile gears
« Reply #9 on: April 18, 2016, 07:23:21 PM »
You just playing or trying to get round wins in, will determine gearing right.

Bracket racing works best rolling the front tires thru the staging beams for consistency in any conditions. Not the easiest of things to do with a front motor cars. That's why ya don't see many bracket racing, let alone getting wins in. More gear less tire for brackets.  ;)

Offline wideopen231

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Re: 1/8th mile gears
« Reply #10 on: April 19, 2016, 11:36:06 AM »
Scott,

If don't mind more on your thought of more gear and less tire for bracket comment. Seems your in favor of spinning tire more.Wouldn't that inturn hurt consistency on questionable tracks?Wouldn't more weight on frontend be better for keeping fronts in lights? Not saying add more just put more stuff towards front some. Maybe better to do in  PM or another thread so as not to highjack this one.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline masracingtd1167

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Re: 1/8th mile gears
« Reply #11 on: April 19, 2016, 02:25:34 PM »
Chris is 100 percent right ! Try and take the weight that you have and get it as far forward as you can . Over the winter I moved even more stuff to the front of mine . My ignition box primer tank and primer pump are now all the way up front and the total weight is as much as the lead bar I had in the front .Even a long wheelbase car will try and pop the wheels up at the hit so it is something you have to deal with and make adjustments from there . What I try to do with mine is keep the wheelie bar low enough so at the hit the tires squat and the bar hits and the front end stays down . As the car moves and comes up on the tire it will drive the front end up a little but it dose not matter because you are past the starting beams . 

Offline Scott Krieger

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Re: 1/8th mile gears
« Reply #12 on: April 19, 2016, 08:26:46 PM »
Yes with putting a big fuel tank and two batteries and what ever else you can as far forward on chassis as possible. :)

wideopen,

More/Taller gear meaning, going from 4.30 to like a 3.90 gear. Calmer launch more MPH.

I like the 4.30 gearing retoboy has now, just a lot of tire 31/13/15 M/T for 400hp. I'd try airing the tires up around 7-8 lbs. to try and get some tire off the track and see if it can spin them. If not keep airing up 1/2 pound till it starts to spin a lil on launch, then back down 1/2 pound.


Offline wideopen231

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Re: 1/8th mile gears
« Reply #13 on: April 20, 2016, 05:28:25 AM »
Ok taller I understand it was the more part had me thinking you meant lower gear.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline Van

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Re: 1/8th mile gears
« Reply #14 on: April 20, 2016, 06:04:55 PM »
My approach to this is very different. I run a T400  = 3 speed. I run a 354 gear and 33 tire. My 1/8 mile times are just about the same as most 7.60 NE1 cars run in the 1/8 using shorter tires & lower gears. Doing the math I think it's real close to the same RPM across the board with the Power glide crowd. I recommend a 390 or 410 gear for the Mopar 360 and spend the money on a good converter & work with the tune up. I have never seen the real need to change gears for 1/8 mile when using a 3 speed as the high gear shift is much later and with the right tire and gear not made until after the 1/8 mile. Done right the car will think it's just a 2 speed ( with 1/8 mile gears). Things to think about.

 Can you post up a time slip so we can see the brake down  on your runs.  PS I have a NOS set of W2's out in the shop, those would wake up that 360 !!
« Last Edit: April 20, 2016, 06:18:11 PM by Van »