Engine/Tranny Question

[Stan Back]

Tom --

I used to have shifting problems with my Super T10 (?) and I believe it was Tex Racing that rebuilt and/or modified my Hurst shifter.  Apparently the $99 Indy shifter mechaniism and the more expensive models are basically the same.  I had them "tune it up" with their own rods and levers and haven't had a problem since.  And I didn't pay for the reverse set-up they offer and saved a few bucks.  You might talk to them about the shifters, too.

Stan

[desotoman]

Tom G.
Emailed you last night but got an error message back. Sent it again this morning. Let me know if you got it,
Thanks,
Dave Haller

Dave,

Got your email last night and the one you sent this morning. Just replied with an email.

Tom G.

[Rex Schimmer]

Dave,
I ran some numbers using your ratios and several things that you might think about. At 7500 rpm in second you should be going around 182 mph so when you shift into high the engine should pull down to 5050 rpm and you said it goes down to 4700 rpm, this may be simply the speed at which the 400 shifts. It takes so long that the car actually slows down before top gear is engaged. You might also think about turning the engine tighter in second gear, if you went to 8000 rpm your engine should then be at 5400 in top gear and maybe this is closer to your max torque range and the engine will continue to pull. A good big block should easily be able to go 8000 even 8500 in second. At 8500 you would be going 206 mph and the engine would pull down to 5750 rpm going into top gear.

As Doug and Sum say the real solution is more and closer ratios. The general rule of thumb on picking ratios is that each step should be about 1/2 of the previous step. Look at Doug's ratios, the difference is .55 first to second, .25 second to third, .17 third to forth and .1 forth to fifth. Very good selection, it mostly has to do with aero drag being a square function.

Rex

[SPARKY]

I have driven a AT 400 with 30" and 2.47s---ran 267. with a 509---I would advise what several have recomended---put it on a DYno and work with a BOAT eng. builder!!!!!!!!!!!

[Dave Haller]

Okay guys, I'm starting to see the light here. I will put the engine on a dyno. There are a couple available up this way. Once I do that I have arranged to have more work done on the engine if needed. The transmission change will have to happen. I am looking at racingjunk.com and see several options out there. Like most of you I am on my own dime on this thing so I need to be frugal but understand the need for bulletproof parts to survive. Thanks for all the suggestions and help. Listening to the very fast ones out there you can hear the rpm drop in higher gears and it isn't much.
Dave Haller

[fwillyj]

-x

[jl222]

I'm in a bit of a delema. I have a 481 inch BBC, running a Ron's Terminator Injection system hooked up to a Turbo 400 that has been beefed up. I ran with no problems at Speedweek 08. The engine came on strong in first gear, 2.48, second gear 1.48, then dropped to 4700 rpm in third, 1 to 1, and lugged to the best of 5900 in that gear. I kept changing out the rear end gears ending up with a 2.47 and speed of 213 which is way low for what I was trying to do. Shift points in 1st and 2nd were 7500 rpm. I'm running methanol for fuel, compression in the engine is about 13:1. Tires are the M/T 30", fronts are Goodyears 23". I know my scoop is way to big and the engine compartment is open. Any suggestions on horsepower needs, transmission gearing, transmission recomendations. I know Danny Boy shifts quickly with a Liberty trans with minimum rpm drop between 3rd and fourth as well as fifth. Any help is much appreciated,
Thanks,
Dave Haller #93 A/FL

  Dave
  It sounds more like a tuning problem to me. Unless your lakester is carrying tons of weight, what does it weight?
 I know Bob Joenck use to run high gear only in his roadsters and ran a lot faster than that on gas.
                                               
                                                   JL222



           

[jl222]

I have driven a AT 400 with 30" and 2.47s---ran 267. with a 509---I would advise what several have recomended---put it on a DYno and work with a BOAT eng. builder!!!!!!!!!!!

 Congratulations Sparky 300 + NA what an accomplishment!
  On your 267 run my program calculates about 7800 using 247s -30" tires with no growth 13 ft frontal area and .5 cd [guessing on fa and cd] and shows 1110 hp to go that fast. If i knew the actual hp numbers and frontal areas i could get closer numbers on cd,  but thats the numbers I needed to input to get that speed.
 If i knew your 300 mph hp and frontal area? But you might want to keep your speed secreats

                                 JL222

[SPARKY]

with the 2.47we were turning about 7300---at 269.--Dave the AT 400 is a good choice in my opinion---shift at 8 it comes back into the high 5's 

[SPARKY]

We have a real soft shift set up almost stock---we do not want to shock the tires---the eng pulls down, the trans slips some and the tires spin a little---we usually lock up again at arount 57-5800 with the 400---this meet I was running a 2 speed PG---shiffed at 8000---pulle down to 43-4400 after shift---thinking of raising that to 8200 trying to get 2 runs over 300.---do not know what my frontal or CD is---sorry

[racergeo]

  My car worked fine on a chassis dyno with a PG and no convertor. Turbo has way more gear in low so should start rollers easily. I was short shifting because of tire spin and pulling the engine to 4000rpm but still ran 237 to the 1/4. In a perfect world a 4 or 5 speed may be ideal, but if you don't have aero and traction, with a ample dose of H.P.what does it matter? Sparky's PG equipped lakester @ 300mph says it all.

[Sumner]

 ..........Sparky's PG equipped lakester @ 300mph says it all.........

He also has a gear vendors in there also, but i'm not sure exactly how he was going through the gears this year even though I think he told me  ,

Sum

[jimmy six]

Great accomplishment Sparky. I have some minor observation to make in the class you are running. Your record, lucky set at the end of the week, took one set earlier in the meet by Seth. (Oh-O) If I were you I would be at the WF first in line and get your 2-300's set quick; if you blink the record might be a bunch over the 299. I'm sure Seth and crew will be coming after ALL the lakester records he has the set with the earlier car and lost.

Knock-um dead Spark and get that Blue Hat..........JD

[SPARKY]

JD---I know that you seeing it the same way as I do---I know that my time is most likely very well limited---I just had slightly less new car Problems than Seth---I have been "Highly motivated" since I heard what Heads he ordered!!!!!!!!when he first started the car---I am going to be spotting him 2-300 hp --- my dumb Home Depot biginers luck will not luck out forver!!!!!!!

[Hans Blom]

Dave, as said before get the motor dyno'd, once you have a hp number you can figure a pretty accurate cd number for your car. As others have been saying you 'should' be able to run faster and probably can with the HP you have now. once you have your aero data you can plot a curve of speed vs hp for your car. Then you can overlay a plot of your rpm and HP over that plot and you see exactly WHAT rpm you need at a given speed in order to beat the aero drag. Keep that HP on the left side of the drag line!  With a little math you can insure the new tranny ratios you are proposing will have enough margin.  There is some very good advice on percent drop with each next gear, this alone will get you pretty much where you need to be but having some hard numbers...even if it's hard to get them right on, you will be close. Use the speed and rpm you hit the wall with the coinciding HP you will find at the dyno and your off to the races....but as always..racing on paper is much easier...and your results will vary..but hopefully in a positive direction...geting the right HP and driveline combo is half the fun, it has taken us 4 years or so trying to get a record on our GMR with a big block..finally got the A in August...that damn Murphy guy is an asswipe.