datsun71 Posted January 1, 2010 Share Posted January 1, 2010 i have a s30 with a built 383 sbc all motor with th350 tranny (torque converter 2600) with r180 rear diff, here the thing it bothering me....why gear ratio it too short...th350 come with 3 speed...i shift every gear at 9000rpm on my autometer tach...YES 9000RPM...by end of 3rd gear im at 120mph on the datsun oem speed gauage..but it not the end of a 1/4 mile yet.... my goal is hitting 10sec on a 1/4 mile with nitrous HELP ME.....WHAT IS THE SOLUTION.... Quote Link to comment Share on other sites More sharing options...
datsun71 Posted January 1, 2010 Author Share Posted January 1, 2010 help.....help Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 1, 2010 Share Posted January 1, 2010 (edited) It would sure help to know your tire diam. and rear gear ratio,and the rpms your running thru the lights and launching at the line at. and any 383 that sees a true 9000rpm is doomed to a short life expectancy, I'm sure, most guys reading that 9000rpm assume your either b.s,ing or your tachs defective, as theres no way an auto trans without full manual control shifts at 9000rpm without being damaged, and even then its on borrowed time Edited January 1, 2010 by grumpyvette Quote Link to comment Share on other sites More sharing options...
johnc Posted January 1, 2010 Share Posted January 1, 2010 HELP ME.....WHAT IS THE SOLUTION.... Fix your tach? Quote Link to comment Share on other sites More sharing options...
John Scott Posted January 1, 2010 Share Posted January 1, 2010 http://www.wallaceracing.com/calcmph.php Even with my lowly 383 7000 rpm, my 3.7 rear and 225 50 16s are nipping at 140 mph when I'm in 4th 1:1 Hmmm. maybe your trannies stuck in 2nd gear or perhaps the tach is set for six cylinders. Using my tire size, 3.5 rear, and 9000 rpm in 2nd gear ratio from a T 350 of 1.52:1, that computes to 123 mph!! Quote Link to comment Share on other sites More sharing options...
datsun71 Posted January 2, 2010 Author Share Posted January 2, 2010 the tire size 225/60/14r......it could be my tach be default, rear end diff 3:7...i think....the lunach at 4000rpm..... Quote Link to comment Share on other sites More sharing options...
deja Posted January 2, 2010 Share Posted January 2, 2010 Uh yeah, its your tach. At 6500 rpm you should be doing 128.6 mph If your tach is accurate your would be doing 178 mph at 9000 rpm. I don't think you're doing that before you get to 1/4 mile! Quote Link to comment Share on other sites More sharing options...
datsun71 Posted January 2, 2010 Author Share Posted January 2, 2010 if the tach to be fix....my gear ratio still too short for a 1/4 mile... Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 2, 2010 Share Posted January 2, 2010 (edited) your current set up results and if your tachs reading 9000rpm its probably set to read a six cylinder engine, and your really running at about 6600rpm ******************************* Final Gear Ratio : 3.73 Tire Size : 225-50-14 Max Power RPM : 6000 Limit RPM : 6500 ******************************* ********************* Gear Ratio Compound ********************* 1 2.520 9.400 2 1.520 5.670 3 1.000 3.730 *************************************** Gear MPH/1000 MPH @6000 MPH @6500 *************************************** 1 7.24 43 47 2 12.00 72 78 3 18.24 109 119 ********************************* MPH RPM (in Gears) ********************************* 1 2 3 ********************************* 5 691 417 274 10 1382 833 548 15 2072 1250 822 20 2763 1667 1096 25 3454 2083 1371 30 4145 2500 1645 35 4835 2917 1919 40 5526 3333 2193 45 6217 3750 2467 50 4167 2741 55 4583 3015 60 5000 3289 65 5417 3564 70 5833 3838 75 6250 4112 80 4386 85 4660 90 4934 95 5208 100 5482 105 5757 110 6031 115 6305 120 6579 ********************************* Gear Change RPM drop (change @6000) RPM drop (change @6500) ************************************************************* 1->2 -2381 (To 3619) -2579 (To 3921) 2->3 -2053 (To 3947) -2224 (To 4276) ************************************************************* in an ideal world you swap to a WELL BUILT 700R4 with full manual controls, and get results that change to those below ******************************* Final Gear Ratio : 3.73 Tire Size : 225-50-14 Max Power RPM : 6000 Limit RPM : 6500 ******************************* ********************* Gear Ratio Compound ********************* 1 3.060 11.414 2 1.630 6.080 3 1.000 3.730 4 0.700 2.611 *************************************** Gear MPH/1000 MPH @6000 MPH @6500 *************************************** 1 5.96 36 39 2 11.19 67 73 3 18.24 109 119 4 26.06 156 169 ******************************************** MPH RPM (in Gears) ******************************************** 1 2 3 4 ******************************************** 5 839 447 274 192 10 1678 894 548 384 15 2516 1340 822 576 20 3355 1787 1096 768 25 4194 2234 1371 959 30 5033 2681 1645 1151 35 5872 3128 1919 1343 40 3575 2193 1535 45 4021 2467 1727 50 4468 2741 1919 55 4915 3015 2111 60 5362 3289 2303 65 5809 3564 2494 70 6255 3838 2686 75 4112 2878 80 4386 3070 85 4660 3262 90 4934 3454 95 5208 3646 100 5482 3838 105 5757 4030 110 6031 4221 115 6305 4413 120 6579 4605 125 4797 130 4989 135 5181 140 5373 145 5565 150 5757 155 5948 160 6140 165 6332 170 6524 ******************************************** Gear Change RPM drop (change @6000) RPM drop (change @6500) ************************************************************* 1->2 -2804 (To 3196) -3038 (To 3462) 2->3 -2319 (To 3681) -2512 (To 3988) 3->4 -1800 (To 4200) -1950 (To 4550) ************************************************************* read thru these and the sub links http://forum.grumpysperformance.com/viewtopic.php?f=45&t=2042&p=5443&hilit=+tire#p5443 http://forum.grumpysperformance.com/viewtopic.php?f=71&t=555 Edited January 2, 2010 by grumpyvette Quote Link to comment Share on other sites More sharing options...
deja Posted January 2, 2010 Share Posted January 2, 2010 Grumpyvette, has stats but he has 225/60/14 not 225/50/14. BTW datsun71 did you change the speedometer gear for the 3.7 rear rear? In other words are you sure your speedometer accurate? Looks like you might need some taller tires, like 26" slicks. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted January 5, 2010 Share Posted January 5, 2010 I would think that taller tires would be the best (cheapest) way to solve the problem. The other thing would be to swap the 3.7 R180 for a 3.54 R200 (along with the other assorted bits in the rear for the conversion). In my mind, these are the cheapest 'fixes'. Next would be the transmission. How does an R180 live behind a 383 in drag racing anyway? Davy Quote Link to comment Share on other sites More sharing options...
datsun71 Posted January 6, 2010 Author Share Posted January 6, 2010 thank everyone okay what size of tire and rim is best fit at the rear wheel housing with no modification for drag racing....i think it is my tire is too small...every time i took off i think my tire not grabbing...and my rpm flying so fast that i just have to shift it....is it okay i run on suspension...r180 will upgrade to r200 soon... my goal to run in the 10 in 1/4 mile Quote Link to comment Share on other sites More sharing options...
deja Posted January 6, 2010 Share Posted January 6, 2010 From what I understand to fit in the stock wheel well you need slicks 26/15x8.0 with 4.5" backspace. Weld Wheel makes exactly the wheel you need. Quote Link to comment Share on other sites More sharing options...
datsun71 Posted January 6, 2010 Author Share Posted January 6, 2010 thank 26/15x8 will it get me into the 10sec 1/4 mile easy...i was thinking 26/10/15 with spacer... Quote Link to comment Share on other sites More sharing options...
deja Posted January 6, 2010 Share Posted January 6, 2010 That 10" rim will probably put the tires into the fenders. I have some Weld Wheel 9" with 4.5" backspace and 235x15 drag radial that won't fit under my stock fenders. You would probably need some flares. thank 26/15x8 will it get me into the 10sec 1/4 mile easy...i was thinking 26/10/15 with spacer... Quote Link to comment Share on other sites More sharing options...
GRUMPZ Posted January 6, 2010 Share Posted January 6, 2010 What did the time slip say? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.