1/8 mile gearing

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hotrodhp
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1/8 mile gearing

Post by hotrodhp » Tue Jun 14, 2016 7:44 pm

I need some help with the rear gear selection. I have a small block, 3300lbs,28" tire and need to be at 7000 rpm at the traps. I have a Rossler Turbo 400 for a trans. Now I have a 4.30 and can stand more gear. Now I'm at 97mph. Thoughts?

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Re: 1/8 mile gearing

Post by bigjoe1 » Tue Jun 14, 2016 7:55 pm

Once you get close to where you want to be, the exact RPM through the traps will make very little difference in you ET for the 1/8 mile. I have worked with several cars, and getting the exact RPM you want MIGHT be worth one, two or three hundredth. It is not very cost effective if you are buying rear end gears every time, If you are way off, you might see a little more improvement, but not much. Of coarse, the slower the car is, the more room there is for improvement


JOE SHERMAN RACING

hotrodhp
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Re: 1/8 mile gearing

Post by hotrodhp » Tue Jun 14, 2016 8:10 pm

Right now the best 60' the car will do is 1.70 w/trans brake and 5700 stall (pro torque converter). This is a 525hp small block with full caltracs setup in the rear. Last weekend I had it to the track and wasn't using all of 3rd gear and thought I might pick up my 60' while coming close to using more of my gear at the end. I've played with some online gear ratio calculators and just was curious if anyone had combos close to this and what gear they were running.

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Re: 1/8 mile gearing

Post by VegaJohn » Tue Jun 14, 2016 10:15 pm

What tires do you run? I've set up 4000lb pick ups that 60 foot in the 1.5s with only slide a links. I think you have something other than gearing hurting your 60 foots

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Re: 1/8 mile gearing

Post by hotrodhp » Tue Jun 14, 2016 10:31 pm

28x9 Hoosier slicks. I also think I need to look at front suspension. Right now I only have a set of cheap 90/10's (competition engineering) shocks on it. I'm looking to buy some moroso trick front springs and some better control arms to free up the front end.

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Re: 1/8 mile gearing

Post by VegaJohn » Tue Jun 14, 2016 10:44 pm

hotrodhp wrote:28x9 Hoosier slicks. I also think I need to look at front suspension. Right now I only have a set of cheap 90/10's (competition engineering) shocks on it. I'm looking to buy some moroso trick front springs and some better control arms to free up the front end.
If you have those poly bushings make sure the pivot bolts aren't too tight. I've seen it several times. The front end won't lift and transfer weight and you'll never hook. What tire psi do you run?

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Re: 1/8 mile gearing

Post by hotrodhp » Tue Jun 14, 2016 10:47 pm

10-11 psi.

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Re: 1/8 mile gearing

Post by ijames » Wed Jun 15, 2016 9:44 am

The easy way to simulate more gear is to borrow some 26" tall slicks if you can, will be the same as changing to 4.6 gears.

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Re: 1/8 mile gearing

Post by Steve.k » Fri Jun 17, 2016 11:11 am

I'm also racing 1/8 mile. We recently did mods to engine that bumped our rpm to 7200 from 7000. We were crossing the traps at 5500 ish now with power band up it feels laggy in third. We have 5.14 gear and 32 tall tire. Think we need closer to 6.0 gear. What do you think?

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Re: 1/8 mile gearing

Post by F-BIRD'88 » Fri Jun 24, 2016 8:58 pm

If you want to trap @ 7000 rpm @97 mph in the 1/8th yod want 5.57 gears.


What is the true tire rolling diameter?

ground to axle center loaded x2 = that.

true weight w driver? peak hp rpm? cid?

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Re: 1/8 mile gearing

Post by Steve.k » Sun Jun 26, 2016 10:15 am

Thanks I'll do some calc. The weight is 2980 and pk hp rpm 7300. 358 cubes. We bumped our shift rpm to 7300 last weekend and car picked up. Ran our best of 6.87@99.44 in 1/8. We have not dynoed this engine so feeling our way around to peak hp rpm. My desktop Dyno says 7500 so we inching our way up. =D> 65 mustang coupe, 358 iron headed Cleveland,850 quickfuel,flat tappet cam .657 lift 260-264@.050 on 106 set at 102, 1 7/8 header 5500 convertor, c4, 5.14 gear, 32x13.5w Hoosier ! We had aDA of 5800ft that day!

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