How much time will I get if I go from a 342 gear to a 373?

86mino · Spanner Necoa #: 1859 Joined: Nov 26, 2003 Posts: 5

Hi Everyone I am new here. I have a question about gears. I currently have a 86 El Camino that I am fixing up. I have a 350 engine int it with 390 horse power, tranny is a TCI 350, and I am running a 342 gear in the rearend. I took it to the track hear in Middle Ga. at Silver Dollar Raceway. It is a quarter mile track and ran a 14.235 at 97.3 miles an hour. I want to know how much time can I pick up with a 373 gear or a 411 gear and at what speed will I be at. I would like to get around 110 miles an hour in the quarter. Thanks for any help that you might be able to give me

greasy5thwheel · Posted: Wed Nov 26, 2003 12:40 pm Post subject:

not much info to go on, but i'll step out on the limb and say that the 4.10-4.11 will put you at 110 at about 6000 rpms give or take a little depending on how much slippage you have in the tranny. probably drop your et by about 3/4 second if you can get it to hookup so mid 13's. i based all this on 26" tires and guess you are going through the lights at about 4300 rpms now. not knowing where you got your 390 hp rating from kinda makes it hard. low rpms or high. your speed vs. et also tells me you are having traction problems now so the steeper gears are only going to make this problem worse. oh yeah, assuming the 26" tires the 3.73 gears will put you through the lights at about 5500 rpms and should get you about 3-4 tenths again with the traction problems at around 103. just my .02 worth. hope this helps.
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86mino · Spanner Necoa #: 1859 Joined: Nov 26, 2003 Posts: 5

the 390hp is at the engine. I don't know what hp I have at the rear wheel. I have headman ellite headers and am running true dual with out cat conveters. I have P275/50R15 BF Goodrich Comp T/A Drag Radials on back. The engine is new and so is the tranny with only 1500 miles on it. Rear end was just re-built with the 342 gear.

86mino · Spanner Necoa #: 1859 Joined: Nov 26, 2003 Posts: 5

The guy that built my engine sent me a sheet with the hp rating of my engine. He said that I would get the best out of my engine if I shifted at around 5500 rpm.

87last1 · Posted: Wed Nov 26, 2003 4:13 pm Post subject:

Was that how much Fine or how much Time??[Just kidding] I Do`nt know about ETs and such,But I pulled a 3:42 out of my 87 with a little 305 and a 200 4R ,replaced it with a 3:73 posi. out of a 87 MCSS and it really come to life.I do`nt know if you`re concerned about the speedometer being correct or not,I had to get an adapter to correct mine.My EL started out with a 2:56 than a 3:42 and than a 3:73,"finally got what I want".

427chev67 · Posted: Wed Nov 26, 2003 6:07 pm Post subject:

I hope you don't do a lot of highway driving. The 3:73's work good on the strip but they stink on the highway without an overdrive tranny. I had 3:73s in my '81 with a th350 and would scream down the road at 3500 to 4000 rpm. Old ladies in mini vans passing me by. You might think about an overdrive trans, they have a deeper first gear for even more grunt off the line and still have good cruising rpm's for 3:73's or 4:11's. If all else fails try some nitrous.
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