410s or 430s???????????

[babiixoxbritty]

lookin for a little advise to see if it would help to go to 430s from 410s. the cars combo is afr 165s,stelth intake,575 demon carb, f cam, stock 90 bottom end, tremmic tko 600. the cars best time has been 12.48 a 112mph, but usually does 12.50s to 12.60s at 111 with 1.74 60 ft times. it goes through the traps at about 5800 rpms and the rev limit is 6300. car is runnin on 26 in tall bfgs. just wondering if anybody had any advise on this before i swap, i dont want to loose any top end and ive heard i might. appreciate any opinions.

[Sharad]

it might spin more with the 4.30s. How well does the car hook?

[MADMOD]

Don't fear the gear!

[babiixoxbritty]

depending on track conditions, it usually hooks pretty hard and i'm also getting some e/t streets. usually 1.7 to 1.8 sixty ft times. i don't want to sacrifice my mid range kick racing abilities. some people say that it will but i don't know.

[Jeff88coupe]

I alway try to gear my car so that the shift light comes on just before I go threw the traps. What is your shift rpm? You can play around with an online gear/tire size calculator to get you close to what your ideal rearend gear should be.
As an example..i use to run stock shortblock 302 gt40p head combo in my coupe ~7 years ago. I ran 4.30's with 28x9 slicks at the track. I shifted it at 5800....it would go 12.2's at 110 with mid 1.6 60's.

[babiixoxbritty]

thats inpressive, my shift point is around 6200 and i have about 500 rpms left at the end of the 1/4 so i think im gonna try the 430s. what was the rest of the combo you were runnin when you ran the 12.20s?

[flyin2jz]

I have 4.30s in my car and its shifted at 6800 and goes thru the traps at 7k with a 26in tall tire with a t5 tranny..just a little info. Kevin

[Jeff88coupe]

thats inpressive, my shift point is around 6200 and i have about 500 rpms left at the end of the 1/4 so i think im gonna try the 430s. what was the rest of the combo you were runnin when you ran the 12.20s?


Stock 302 shortblock, ported gt40p heads, gt40 intake with ported lower, mild HR cam (.513 lift), 65mm t/b, 76mm mas, 1 5/8" lt, 2 1/2" exhaust and dumps, fms HD clutch, tremec 3550, 4.30's, basic drag suspension front and rear. Drove it like I hated it. It went a best of a 12.19 at 110 n/a...and 10.98 at 126 on a 200 wet shot (with only a 1.65 60')

[babiixoxbritty]

Thats awsome, ill be spraying with a 100 shot soon. I got a 87 notch with the same combo as this car but its fuel injected, havent ran it yet but my buddy and me have a carb vs. fuelie competition, tryin to solve a long time argument. lol

[PHAT69AMX]

More gear most likely will lower the trap speed.

For 110 mph ideal E.T. is 11.90 sec. per Moroso Power Speed Calculator
For 12.50 sec. E.T. ideal mph is 104 per Moroso Power Speed Calculator
So from that it looks like some more gear would help.

So we'll use a 110 mph = 9680 ft per min.

26 inch dia tire (pure) = 26 x pi = 81.68 inches = 6.80 ft circumference
Actual working tire dia is a little less due to tire squish from cars weight that reduces the radius.
This will increase the rpm's in the caclulations a couple few hundred.

9680 fpm / 6.80 circ. = 1425 rpm @ tire = 26 inch tire (pure) @ 110 mph

1425 rpm tire @ 110 mph x 4.10 gears = 5845 rpm motor with 1:1 trans 4th gear

1425 rpm tire @ 110 mph x 4.30 gears = 6130 rpm motor with 1:1 trans 4th gear

Let me guess, are you currently running 3.91 gears ?
111 mph = 9768 fpm
5800 rpm motor existing
25 dia tire (effective) = 6.545 ft circ
9768 fpm / 6.545 circ = 1492 rpm tire
5800 / 1492 = 3.89 gears ( existing ? )

:cool2:

[PHAT69AMX]

Let me guess, are you currently running 3.91 gears ?
working backwards
111 mph = 9768 fpm
5800 rpm motor existing
25 dia tire (effective) = 6.545 ft circ
9768 fpm / 6.545 circ = 1492 rpm tire
5800 / 1492 = 3.89 gears ( existing ? )

So using the "reduced" 25 inch "effective" tire diameter

25 dia tire (effective) = 6.545 ft circ

110 mph = 9680 ft per min.

9680 fpm / 6.545 ft circ = 1480 rpm tire (25 inch "effective" dia )

1480 rpm tire @ 110 mph x 4.10 gears = 6068 rpm motor with 1:1 trans 4th gear

1480 rpm tire @ 110 mph x 4.30 gears = 6364 rpm motor with 1:1 trans 4th gear

Looks like 4.30 gears will give 6300 rpm motor at 110 mph using 25 inch effective tire dia.

:cool2:

[babiixoxbritty]

thanks, thats helpful, i guess weight and traction are why my e.t.s are a little off, its weird that on some passes i hook harder, get a better e.t. but less m.p.h., on others i spin more get a slower e.t. and 60 ft. but a faster trap speed.

[babiixoxbritty]

please delete