Nealio240z Posted August 2, 2007 Share Posted August 2, 2007 Has anyone ran a th350 tranny w/ 3.90:1 gears in the 1/4 mile??? If so what was your trap rpm at crossing? Im worried that this combo in my 240 will top out in rpms before I reach the finish line... I got about 300hp, 27" tall tires, and a th350 w/1500 stall converter, 6000 rpm rev limit. With 3.36:1 gears, I crossed at 4500 rpms or so... I was just wondering what any of you have expeirenced in this matter... Thanks for the input. Quote Link to comment Share on other sites More sharing options...
280zwitha383 Posted August 3, 2007 Share Posted August 3, 2007 With a 3.90 and stock tires I was hitting right at 5k in the 1/8th. I have a 2500 stall converter and I should have 450hp/450tq. In reality I probably have/had less hp than that because at the time I was running out of 1 1/2" headers and a single 2.5" exhaust. I have also never messed with the jets at the track because I don't think it will do any good with the skinny tires I am running. This is also in a ZX which is generally accepted to be heavier also so that might even out some of the power difference. You can also manually type in your transmission gears and differential ratio. http://www.geocities.com/z_design_studio/ I was hitting 88mph in the 1/8th and I was pretty sure I wasn't at 6k like this thing says I should be but that's what this calculator says and that's without the torque converter spinning. Use 4th gear to figure out the top end as that is the 1:1 ratio of the 5 speed. It looks like 110+ is about an 11 second or low 12 second 1/4 mile time which you're probably not going to do so you should be good? Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted August 3, 2007 Share Posted August 3, 2007 don,t forget tire dia. effects results also http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html HERES OTHER INFO LINKS http://www.wallaceracing.com/reargear.htm http://users.erols.com/srweiss/calcmph.htm http://users.erols.com/srweiss/calcrpm.htm http://users.erols.com/srweiss/calcrgr.htm http://users.erols.com/srweiss/transc.htm#tabtop http://users.erols.com/srweiss/transc.htm#Auto Quote Link to comment Share on other sites More sharing options...
drzed Posted August 3, 2007 Share Posted August 3, 2007 3.90's should work out just about perfect. My 3 spd auto has the same 1:1 top gear as yours but maybe a bit looser converter. I run 11.17 @120 and run thru the lights at about 6700 RPM on a 26" tall tire. I have a little more power than you and a slightly smaller tire so this combo should work out great for the track IMO. It's a little buzzy on the freeway but I'm willing to live with it. Quote Link to comment Share on other sites More sharing options...
typhoone Posted August 3, 2007 Share Posted August 3, 2007 don,t forget tire dia. effects results also http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html HERES OTHER INFO LINKS http://www.wallaceracing.com/reargear.htm http://users.erols.com/srweiss/calcmph.htm http://users.erols.com/srweiss/calcrpm.htm http://users.erols.com/srweiss/calcrgr.htm http://users.erols.com/srweiss/transc.htm#tabtop http://users.erols.com/srweiss/transc.htm#Auto you always post useful links, do you just have all of these copy and pasted in a word document under certain subjects? you are probably one of the top 3 most helpful contributors on this forum. Quote Link to comment Share on other sites More sharing options...
Pete84 Posted August 3, 2007 Share Posted August 3, 2007 you always post useful links, do you just have all of these copy and pasted in a word document under certain subjects? you are probably one of the top 3 most helpful contributors on this forum. Grumpy is everywhere, over on http://www.thirdgen.org/ too. Great stuff. If I ever get around to a SBC or BBC, I know whom to ask Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted August 3, 2007 Share Posted August 3, 2007 if your serious about building engines and cars youll keep records and easy access to the data you use or need, Ive got 8 gigs of hard drive info on the cars and engines Ive built and the data used to build them, I hate randomly searching for stuff I know Ive used in the past so I keep most info/data under files in the shop computer and duplicated on the house computers hard drive Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 3, 2007 Share Posted August 3, 2007 if you are crossing the lights at 4500 rpms with a 3.36 you will now be crossing at 5223 with a 3.90. Sounds like you have some rpm room left over. 4500 rpm, 27 inch tire, 3.36, 1:1 top gear makes a 107.5 mph trap speed (in theory). 6000 rpms, 27 inch tire, 3.90, 1:1 top gear would make a 123.5 mph trap speed. My car traps at 135mph in 4th gear (1:1, T5, 26 inch tire) at 6800 rpms. Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted August 3, 2007 Author Share Posted August 3, 2007 That has been most helpfull. Ill give it a try and if I dont like it I can always change it... Thank you Quote Link to comment Share on other sites More sharing options...
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