Starting line Ratio Help

Transmission to Rear-end

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Tom_McDunnah

Starting line Ratio Help

Post by Tom_McDunnah » Thu Mar 09, 2006 4:02 pm

Guys I have a T/S drag car 2002 Camaro 25-1E and I am having a problem trying to find an optum rear gear,
First the car weighs 2609 lbs fully loaded with me in it.
I have a 632 cu in BBC 4.600x4.750

I am running 2 stages of nitrous 1st stage comes on soon as trans brake releases and second stage comes on in about 40' ft out (only have run just one stage so far) tuning my nitrous system (225 shot each system)

Tires are 33 inch diameter Hoosiers with 103 3/8 circumference.DOT Hoosiers Quick Time Pro's 33x22.5x15(just some thing I am trying) They do work good tho,hooked excellent
I am running a T/S Trans 2 speed glide,with a 1.80 1st gear ratio
Also I am running a T/S 10 inch Big Dog Caddy converter
I leave the line between 3800 and 4400 rpms,been trying different rpm's

This engine is capable of turning 8800 rpm's but I don't think I want to shift at that rpm,I want to be more around 8000 to 8200 rpm and the same crossing the finish line.Give or take a hundred rpm

I would like to get 2 sets of gears to run 1/8 and 1/4 mile racing.
I am running a 9 inch ford rear.
I would like to beable to just change out the gear chucks for different tracks.

I have tried 2 different gear ratios so far 4.30 and 3.89,and feel like I have just wasted my time and money.Thats why I came here to ask some of you technical people here for advise
With the 4.29 gear it 60' at 1.10
With the 3.89 gear it 60' at 1.12

With the 4.30(7/30) gear it crossed in the 1/8 mile at 7300 rpm at 135 mph
With the 3.89(9/35) it crosses the 1/8 mile at 6900 rpm at 138 mph
I am looking to achevie optium mph with this combination and I now realise I went the wrong way with the gear swap.
The mph's I posted are with a safe tune up I think there is more mph there as I am still sorting out my nitrous tune up.

I'd feel comfortable to turn this BBC 7800 to what ever it take to make this car work,
I guess what I am getting at,I wanted to use a starting line ratio chart,but the old ATI one I seen only went to a 4 inch stroke crank,
from what I gathered I need to be in the 8 to 12 area for a starting line ratio,thats just a guess.
My last guess at being in the area of 7.002(starting line ratio) did not work I guess

So I am asking if someone here could shead some light on the gear combinations for me, I will need I assume 2 sets of gears,1 set for 1/8 mile and another set for 1/4 mile.

I guess I don't know which direction to take ,I got maybe and idea I am assuming possibley a 4.57(7/32) for the 1/8 and possibly 4.30(7/30) for the 1/4

I am trying to get to 160++ in the 1/8 mile and looking to get 200+ in the 1/4 mile,maybe this is not doable,maybe it is,I just need some professional help here with the math part,I guess I am missing some thing,lol gear ratios and rpms,lol

If I am wrong please help me I only want to do this just 1 more time,the pro gears are killing me,LOL
Any help would be appreciated

If there is anything I forgot to say,ask and I'll try my best to post up the info

Thank You, Tom McDunnah :roll:
Last edited by Tom_McDunnah on Sat Mar 11, 2006 5:02 pm, edited 1 time in total.

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BillyShope
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Post by BillyShope » Thu Mar 09, 2006 6:28 pm

I find it hard to reconcile the lower speed with the 4.3 gearing. I assume this was on a different day. Were atmospheric conditions different? It would seem that you were losing about 8% of the horses on that day.

Pages 2 and 3 of:

http://home.earthlink.net/~whshope

contain quarter mile and eighth mile performance programs. I think you'll find that, for the best speed, you want a gear that will have you turning higher engine speeds as you go through the traps.

Tom_McDunnah

Post by Tom_McDunnah » Thu Mar 09, 2006 7:02 pm

Billy,with the 4.30 gear ratio I had a T/S 9.5 converter in it when it was sprayed with nitrous,
I called T/S and they told me the converter most likely loosened up about 500 to 1000 rpm due to the nitrous,also that time it had a bunch of retard in the engine for the nitrous,

Since then I have added timing back to the engine about 8 degrees.And have been leaning out the fuel mixture.
I then went with the 10 T/S caddy converter and went with the 3.89 gears

Thanks for the link Billy,good stuff

Tom

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Post by BRENT FAY » Sat Mar 11, 2006 2:05 pm

Tom, You might want to contact Tom Hemphill he post on this forum as TSTOM. He has some badass tune ups that make alot of mph. You can visit his website www.hemphillracingengines.com Brent

Tom_McDunnah

Post by Tom_McDunnah » Sat Mar 11, 2006 4:57 pm

Thanks Brent, I did check Tom's site out good looking site,

What I have come up with so far I am going to go with a gear combo in the 4.3 range, but I have three combo's to pick from.
I am running a 103 3/8 circumferance tire and I want to get the best gear for my car,I am considering these 3 gear sets,can anyone elaborate on these gear ratio's? As in what is the power gear and what one would be the mph gear. Thanks guys

4.29 7-30 7 pinion and 30 ring gear

4.30 10-43 10 pinion and 43 ring gear

4.33 9-39 9 pinion and 39 ring gear

I guess if I was talented enough I could figure this out,but I am not good with gearing with math, what I am looking for is the best gear to run for the 1/8
I want to achieve the best mph and et

I am willing to turn this engine 7500 to 7800 at the finishline in the 1/8 mile, maybe I am wrong here with the rpm's I have suggested ,if so correct me.

Tom
Last edited by Tom_McDunnah on Sat Mar 11, 2006 5:09 pm, edited 1 time in total.

TSTOM
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Post by TSTOM » Sat Mar 11, 2006 5:01 pm

Thanks Brent...good to here from you ..do you ever see Bud anymore?

Tom, I would stay with the 3.89 for now and work on the nitrous tuneup for these reasons 1)as you get the nitrous right those tires will not be adequate and you will just be changing gears again 2) with nitrous if you gain 200hp you also gain about 300 ft. lb. tq so the car will tolerate a little taller gear 3) for that engine to only go 138 something more than just the rear gear is off ...post some info about your nitrous tune up or email me direct and we'll see if we can get you straightened out
be careful adding timing ....that is what burns most nitrous engines up
a good nitrous tune up will make a 4000 rpm convertor go to about 6000 rpm on the spray so my guess is that for whatever reason your not getting up on the convertor Do you have a data recorder?

Tom_McDunnah

Post by Tom_McDunnah » Sat Mar 11, 2006 5:53 pm

Tom
Thanks for your response,thats great to hear,I just put them gears in there this past summer,lol
On the data recorder,"I wish" not yet but I have been thinking about one,maybe this year.Up till now its been seat of the pants thing.

This is a new car and I have been trying to do this on my own now for 2 years,getting this car up and going.Hope fully this year I am going to get more time to turn the wick up on this thing. I am getting there but,slowly
I'll get there,as I don't want to get into hurting parts in the engine

Tom I sent you a PM

Thank you,

Tom McDunnah

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Post by TSTOM » Sat Mar 11, 2006 7:22 pm

Returned your pm A data recorder is not really an expense when you consider all the wasted trips to the track and wrong parts purchased
You don't have to have a full blown racepak just something to record & graph at least engine rpm driveshaft rpm and a few analog channels
Tom

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Post by T RICK » Sat Mar 11, 2006 7:48 pm

I agree with Tom get a simple data recorder it will save you a ton of money and frustration. Drive shaft RPM and engine RPM can tell you a lot about gears and convertor efficenices. This is an over looked inexpensive item that cost less then a dyno session.

Rick

Tom_McDunnah

Post by Tom_McDunnah » Sat Mar 11, 2006 9:26 pm

Thanks for the info T RICK and Tom,

I'll have to look into a data recorder,
What companys make these recorders? If you know of any do they have any websites on their products?

Thanks Guys

Tom

T RICK
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Post by T RICK » Sat Mar 11, 2006 10:53 pm

Look at this site they have a low cost one. http://www.rpmperf.com/
A freind of mine is going to try their basic one as it can be up graded later.

Rick

Tom_McDunnah

Post by Tom_McDunnah » Sat Mar 11, 2006 11:26 pm

Yes Rick the basic system is a great value,looks like the "cats meow" for the beginner. I am going to do a little research on a few of these models.


Thanks

Tom

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Post by BRENT FAY » Sun Mar 12, 2006 2:58 pm

TSTOM, BTW Glad to see you on this forum you add alot of very good advice and expertise........ Bud called me a couple weeks ago about doing a SBC for one of his coworkers. I aked him if he's ready to go racing yet,wants to but, he still doing the horse stuff with the two girls till they get older. Wanted to know about M.Hunt on his operation. He's doing well and sold the 57, building a 68 camaro. ..........Tom M, Yeah Tom H (lotta Toms here) is right about 3.89. You can use this gear for both 1/8 and 1/4. You didnt give your ET's. I was trying to figuire convertor slippage. ...........I'm guessing your ET is low 5.0s to teens. ...... With NOS the engine likes to be loaded like a blower to get the most out of it. On Hunts car tried 4.10 from 3.89 and slowed down. Runs 167 in the !/8 now since switching back to 3.89. with 1.72? low gear glide..........Also might want the first stage come in at @.5 to .7 out with the max timing on launch then ramp out slowly while in first stage and faster when 2nd stage comes in. ....shocking the tires/chassis too much? .........Definitly get a data recorder it will save a bunch $$$$........Edelbrock makes one also........nice unit.....but you will need a laptop or PC at the track so fiquire that in on the cost of a unit. Brent

Tom_McDunnah

Post by Tom_McDunnah » Sun Mar 12, 2006 3:59 pm

BRENT FAY wrote:Tom M, Yeah Tom H (lotta Toms here) is right about 3.89. You can use this gear for both 1/8 and 1/4. You didnt give your ET's. I was trying to figuire convertor slippage. ...........I'm guessing your ET is low 5.0s to teens. ...... With NOS the engine likes to be loaded like a blower to get the most out of it. On Hunts car tried 4.10 from 3.89 and slowed down. Runs 167 in the !/8 now since switching back to 3.89. with 1.72? low gear glide..........Also might want the first stage come in at @.5 to .7 out with the max timing on launch then ramp out slowly while in first stage and faster when 2nd stage comes in. ....shocking the tires/chassis too much? .........Definitly get a data recorder it will save a bunch $$$$........Edelbrock makes one also........nice unit.....but you will need a laptop or PC at the track so fiquire that in on the cost of a unit. Brent
Brent you hit the nail on the head with the et 5 teens,

I am running a 7al3 for ignition,so ramping timing in is out with this system,I have chips in the retard for both stages.
That would be awesome if I can get this rocket in the 160 zone this year,thats my goal.

I did have chassis issues the last 2 years I believe, I had my car in the chassis shop,(sgeracecars.com) pretty talented guy,
He found several things that needed attention,4 link, and front struts I believe were to blame for the slow et's.

I am hoping that the car now will handle the power and can further dial in my tune ups,and possible be able to turn on both stages now with the chassis set ups,I'm praying.

I am going to do a little reasearch on the data recorder some,but i am going to talk to someone that has run the a bit,there are a few things I would like to monitor, fuel,eng.vac, rpm,torque converter, drive shaft, not sure on the egt's as of yet.

I was turning the nitrous on .oo1 after the trans brake released and tried 2 nd stage at .800 out, worked great but aborted run 300 ft I believe, worked awesome but wanted to check plugs, all was good,
I went back and just used the 1 stage and continued tuning,

I only got 3 runs on this new 632 this past fall and had to put the car up due to the chassis
It going to be a different ballgame this spring, going to pick up where I left off with the tune up and try to run both stages with the different chassis set up,,should be interesting.

I believe the engine is making good HP where i am at with this (225) 1st stage and (225) 2nd stage,going to stick with that for now.
I am close now with that tune up,but I still can advance the timming a little more,(no heat marks on the grounds yet) but close to getting them,
good fuel ring down inside of porcilin tho, may up the fuel pressure and put little timming back in,1 degree at a time,
My last move I added 1 degree and gained 3 mph, so stuff is starting to happen.

I don't want to make too many changes as I want to see what all this chassis work did to improve the car, I am hoping maybe 2 to 3 tenths is possible, (I'm still praying) LOL
I am going to call Tom tomorrow and talk a bit on some of this and gain some knowlege from him,, but from his post and your post Brent you have given me some inner piece,I thought I was going in the wrong direction,with the gearing, but I guess not!!

I got another thing I may try,but I am going to see where this set up takes me, I got a hunch with the tire size I got I may have to gear uo to 3.70 for the quarter,and if this thing comes alive like I think it may,I just may do that. But that is later on
Thanks for the input Brent and Tom I feel much better

Tom McDunnah

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Post by BRENT FAY » Sun Mar 12, 2006 4:57 pm

I'm glad I could help. But when you talk to Tom H do what he says to the letter,dont run out and ask another 6 people for there advice. He has a ton of R&D he has been there done that, where others just give advice(bad) and doesnt have a clue why it might work. Each eng./car combo are like women! They all desire something different!....... As Charlie Taylor told me...If it's got tits or tires you will always have problems!:lol: ........ You will save alot of $$$ and not be seeing your engine builder each week with engine problems. He will probably give you some mild tune ups and get more aggressive from there once you get things sorted out........ You have to learn to walk before you can run.........and you will be flying in no time. BTW Tom H when is the next outing for your Cuda? Brent

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