1/8th mile gearing question

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VegaJohn
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1/8th mile gearing question

Post by VegaJohn » Mon Apr 20, 2015 9:15 pm

The car is a Vega notchback ladder bars 2520lb race weight. It has a 355 with 12.5 to 1 compression but huge cam 283/281@50 644 lift 104 lobe sep. Powerglide tranny with 4.88 gears. I have never run the car yet and only have 1/4 numbers from previous owner. They were 10.30@ 130mph. I have a shot at getting a centre section with 5.83s and spool for a smoking deal. It will only be used for 1/8th mile. Is it worth switching over? Will that low of a gear make the car too hard to hook. Anyone running a similar set up. He was shifting it at over 7200. I thought maybe it will help overcome the overkill camshaft.

barnym17
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Re: 1/8th mile gearing question

Post by barnym17 » Sat Apr 25, 2015 7:25 am

what tire is on the car? converter etc? Lower gear will tighten converter may offset any gain from gear.I know in my case I switched from 4.10 gears to 5.13 and the the car ran exactly the same number only the rpm at the stripe changed.

VegaJohn
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Re: 1/8th mile gearing question

Post by VegaJohn » Sat Apr 25, 2015 6:39 pm

The slicks are M/T 31x13 et drag. The converter is a JW 5500. If all I'm going to gain is a tenth of so I'll just leave the 4.88s in to save wear on the engine.

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Re: 1/8th mile gearing question

Post by pdq67 » Thu May 28, 2015 11:01 pm

You don't mean "5.38" gears do you??

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wheelsup330
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Re: 1/8th mile gearing question

Post by wheelsup330 » Tue Jun 02, 2015 9:23 am

I ran my 355 combo, in my Vega, when it was Backhalfed, with 30" tires, in the 1/4 with 4.88, 10.30's and went to 5.38 for 1/8th and saw 0 ET change. I was shocked that gear swap did nothing at all.

VegaJohn
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Re: 1/8th mile gearing question

Post by VegaJohn » Tue Jun 02, 2015 6:52 pm

wheelsup330 wrote:I ran my 355 combo, in my Vega, when it was Backhalfed, with 30" tires, in the 1/4 with 4.88, 10.30's and went to 5.38 for 1/8th and saw 0 ET change. I was shocked that gear swap did nothing at all.
Thanks for letting me know. I left the 4.88s in there. Can you tell me what engine combo you had in your 355?

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Re: 1/8th mile gearing question

Post by F-BIRD'88 » Fri Jun 05, 2015 9:06 pm

If the car has good traction and peak engine horsepower occurs at more than 7200 rpm and the enigne has good "afterpower"

(power beyond the HP peak rpm) then the gear change will likely help. if the car has poor traction now it may not help.
Sometimes more gear actually helps the car to hook. You need good (new) tires.

powerglides like more rear gear, especially on small motors that need to rev up high.

A 355 motor like yours should be trapping about 7700 rpm. +/-. (1/4 mile) IMHO it can probabily use more rear gear ratio.
especially if traction is good. especially for 1/8th mile track.

does the car/track have trouble with traction? Consistency? Bracket racer?

Is a bit better ET going to make you more MONEY? Or make you more popular with the girls?

Does the car "leave" hard enough for you or is racing the car about as much fun as watching paint dry?

VegaJohn
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Re: 1/8th mile gearing question

Post by VegaJohn » Sun Jun 07, 2015 4:24 pm

It doesn't leave hard in my opinion. 1.48 is my best 60 foot so far. Our track has premo traction this season. Several cars were pulling wheels off. I also notice my car just seems to come alive after I cross the finish line. I'm really thinking of dropping in a smaller roller cam with a 260/270@50 630 lift roller cam and putting on a nitrous kit for beating up on the odd big block :) oh and a quicker ET won't get me cash or any girls. My wife wouldn't like that lol.

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Re: 1/8th mile gearing question

Post by BirdMan » Sat Jun 13, 2015 9:38 am

I would figure out what rpm's would be with the 5.83 and it will probably work out! You may have to adjust rear end bars and shock settings to get the best setup. 1.88 low gear x 4.88=9.17 final drive ratio, 1.88 x 5.83 = 10.96 final ratio for low gear which should be better launch and of course more trap rpm.
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Re: 1/8th mile gearing question

Post by 1972ho » Sun Jun 14, 2015 5:10 pm

My cars weight is about the same as yours same size rear tire about the same et and mph but my .60ft or 1:39 or better and I run a 5:67 gear and my rpm in the quarter is 8100,But only 7000 in the 1/8 so I figured to get my rpm up to 8100 in the 1/8 I would need like 7:00 or better gear.

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