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02-06-2008 08:00 PM #1
quick ?
I have a quick question you might have seen my other posts but my 87 camaro has ran a best of 12.10 at 113 with 2.73 gears with a th400 trans 26" tires. i only use 2 gears through the 1/4 mile i shift into second at 6700rpm and and cross the line at 6800 rpm in second gear. i had just put a set of 4.10's in it put a 3 gallon cell up front and got some control arm relocation brackets. my question is since i went with the 4.10's i heard my trap rpm will only be like 6100rpm in 3rd will this cause me to run slower time since im not turing a higher rpm like before or will it be about the same. Im hoping to hit around 11.70 . also taking front bumper support off and of course the stock gas tank think i will be able to do it.
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02-08-2008 07:03 AM #2
why no replies to this ?? . you will def be quicker with the new gears regardless of trap speed rpm`s .. probably even more so than you think ..especially if you get some grip and drop that 60 foot time a bunchiv`e used up all my sick days at work .. can i call in dead ?
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02-08-2008 07:34 AM #3
Originally Posted by steve88crx
I am guessing this is a sbc.
To run a 12.10 pass with a 2.73 that is doing very well and would require a very hard-core engine.
In fact I would love to see some specs. on this engine combo.
To add to this back in aug. he was running 13.75's with a 2.15 60 ft. time.
On Nov. 1 he says he is now running 12.10's at 113 mph along with 1.77 60 ft. times.
Pick a story.Last edited by erik erikson; 02-08-2008 at 07:47 AM.
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02-08-2008 08:42 AM #4
when i ran the 13.75 it had 1 broken pushrod and i did not notice till i got home i was going to adjust the valves and i seen it. i had to get new locks beacuse they kept backing off.
350 bored .30 over dart iron eagle 215cc platinum heads with 64 cc chambers , isky 507/507 lift 247/247.50 lift with 108 lsa, victor jr intake ,holley 650dp choke horn milled, 1.5 roller rockers, hyper flat top pistons with 4 valve relief, eagle crank, 1 5/8 longtube headers turbo 400 trans with b@m shift kit red neck 4000 stall..... in the first pass you can hear me shift into second right as i pass the camera the second and third runs i found out later but there was a plug wire on the header and it was breaking up.
YouTube - camaro1
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02-08-2008 08:58 AM #5
Nice vid, cool sound!" "No matter where you go, there you are!" Steve.
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02-08-2008 08:58 AM #6
Originally Posted by steve88crx
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02-08-2008 09:23 AM #7
Originally Posted by erik erikson
Steve,
all else being equal i.e. same trap speed you won't be turning as high but you will get there a lot quicker and will probably pick up some mph so maybe you hit the traps closer to 6500. Let's not forget about converter slip... Good chance you'll trap near the same rpm's
If you're at 12.10 today I would expect something in the 11.7's maybe even 11.68. For your mph of 113, the car should be at 11.9's already and I would expect you'll pick up quite a bit more with the gear.
With the shorter gear, traction becomes more important so if you had any trouble hooking before it will be harder now.
Most of this is pure speculative bench racing with a few slightly educated guesses. Run it and tell us how it turns out!
-Chris
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02-08-2008 10:41 AM #8
I got a 2.73 in a streetrod and I don't particularly like it, sure wouldn't want it a drag car.Bob
A good friend will come and bail you out of jail....but a true friend will be sitting next to you saying..."Damn....that was fun!
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02-08-2008 11:27 AM #9
if i knew that i had a 2.73 in it before i built the motor i definatly would have changed the gears but the guy who had it before me said he had put 3.73 in well i kinda knew he lied the first time i went down the track.
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02-08-2008 11:39 AM #10
Originally Posted by steve88crxIts gunna take longer than u thought and its gunna cost more too(plan ahead!)
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02-08-2008 12:46 PM #11
For TH 400 with a 1.48:1 second gear and 26" tires, at 6800 rpm you are at 130 mph. With a 1.57 second gear you are at 122 mph. Something is slipping or the tires is a spinning. The gears will help tire spin if that's it.
KitzJon Kitzmiller, MSME, PhD EE, 32 Ford Hiboy Roadster, Cornhusker frame, Heidts IFS/IRS, 3.50 Posi, Lone Star body, Lone Star/Kitz internal frame, ZZ502/550, TH400
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02-08-2008 01:27 PM #12
thanks for clearing up the trans gear ratio... I was figuring something like 1.7 from the calculations but didn't know typical 2nd gear ratios in th400. If you figure about 10% converter slip, it works out close to your 1.57 ratio...
-Chris
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02-10-2008 08:17 PM #13
Originally Posted by erik eriksonLast edited by rabid rat; 02-10-2008 at 08:39 PM.
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02-11-2008 06:50 AM #14
ya i hope i get a couple passes in it. i have a 9iinch sitting in the garage im getting it together little by little hope i can get it in by next year along with ladder bars.
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02-11-2008 02:54 PM #15
dana 60
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Welcome to CHR. I think that you need to hook up your vacuum advance. At part throttle when cruising you have less air and fuel in each cylinder, and the air-fuel mixture is not as densely packed...
MSD 8360 distributor vacuum advance