RACING What did I miss? (cry for help)

Clipclop80

Not-quite-so-new-guy
Thread starter
Apr 9, 2021
21
3
If you have the graph for the dyno run, make sure you're shifting at the right rpm. When it changes gears you should be a few hundred rpm below your peak torque. Fixing that 60' time will definitely help too. Should be 1.6 or better.
I have not shifted it at the RPM you suggest...
peak torque is 527 lb/ft @ 4600 RPM. I have been shifting way too high then. peak HP is 523 @ 5800
I have tried at 5500, 6000, and 6500.
 

Clipclop80

Not-quite-so-new-guy
Thread starter
Apr 9, 2021
21
3
You haven’t mentioned your converter - what is it.
You’re crossing the line at 5200-5500rpms , correct? If not then what rpm is it?

And you really need to lose the air shocks. A good set of KYB’s or Bilsteins would help. A set of good drag shocks would be even better.

I agree with Fleming, you need to drop the 60’. A 1.60 puts you under 12. And I’ll reiterate, nitrous will put this in the 10’s. First things first though, converter and shocks?
converter is low: foot brake @ 2100. I must address the shocks. I have focused on UMI rear links, for the 12 bolt conversion, and tires. Rpm at the stripe is just under 5K
 

Streetbu

Know it all, that doesn't
May 22, 2011
2,708
113
Central NY
I have not shifted it at the RPM you suggest...
peak torque is 527 lb/ft @ 4600 RPM. I have been shifting way too high then. peak HP is 523 @ 5800
I have tried at 5500, 6000, and 6500.
I forgot you had a 700R4. The gear ratio split between gears is horrible. 1st is 3.06, 2nd is 1.63. That's a HUGE difference. Makes it very hard to keep it in the rpm band you want. Shifting at 6500 still puts you just under 4k rpm on 2nd. But is way over where you should be in 1st. :/
 
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Clipclop80

Not-quite-so-new-guy
Thread starter
Apr 9, 2021
21
3
I forgot you had a 700R4. The gear ratio split between gears is horrible. 1st is 3.06, 2nd is 1.63. That's a HUGE difference. Makes it very hard to keep it in the rpm band you want. Shifting at 6500 still puts you just under 4k rpm on 2nd. But is way over where you should be in 1st. :/
agreed. it has been suggested to start in 1 st instead of low. yes / no?
 

39F

Master Mechanic
Sep 9, 2019
474
63
Pittsburgh PA
Good to know 39F! can you give any more details on the improvement?
The changes I see to be most effective are to go to 1-3/4" headers, a 3000 stall, deal with the front & rear shocks, and higher flow thru mufflers .
This forum has been an excellent resource for recommendations and advice!
Well the car was more responsive but only gained 2 tens but the 60ft actually went from high 1.60s to mid to low 1.60s and car ran cooler it seemed ,car went best of 10.35@ 131 but I had a 4 speed manual transmission leaving at 5500 at the track ,but also went 10.80s on the street according to my friends draggy ,that 700r4 isn't the worse things having that low first gear but isn't doing you any justice but a little bit looser converter will help you out ,kinda funny good friend of mine has a 68 firebird with a 406 that was close to my 406 at the time and he had a 700r4 and 350 gears in his axle ,and I had a 406 to a t10 4 speed 2.43 1st gear but with 430 gears in my axle and we but had really close 60ft times and would go 11.50-11.70s on motor
 

-dw-

Apprentice
Mar 15, 2021
80
33
Central MN
agreed. it has been suggested to start in 1 st instead of low. yes / no?


Low is 1st. Unless its slipping your transmission isn't your issue. Neither is the 1-2 gearing. (ya ya i hear its not ideal). Still it won't lose 1sec et. Torque converter? Anything special, brand, stall? What headers was is it dynoed with? Small? Maybe? Current headers are probably not 1sec et too small. As said before if the dyno sheet is correct somehow your 406 became only about 375hp in the car. My Olds has run mid 12s, 108-109mph with shitty iron exhaust manifolds and a swap to headers has gone to 12.0, 112-114. Roughly figuring engine hp around 425-440. Puts 375hp to the wheels.
 

Clipclop80

Not-quite-so-new-guy
Thread starter
Apr 9, 2021
21
3
Low is 1st. Unless its slipping your transmission isn't your issue. Neither is the 1-2 gearing. (ya ya i hear its not ideal). Still it won't lose 1sec et. Torque converter? Anything special, brand, stall? What headers was is it dynoed with? Small? Maybe? Current headers are probably not 1sec et too small. As said before if the dyno sheet is correct somehow your 406 became only about 375hp in the car. My Olds has run mid 12s, 108-109mph with shitty iron exhaust manifolds and a swap to headers has gone to 12.0, 112-114. Roughly figuring engine hp around 425-440. Puts 375hp to the wheels.
The converter could be an issue. I have to check with my trans guy who rebuilt the trans and put in the converter but I had requested a 2400 stall but like I said I can only foot brake to 2100. I would bet the dyne runs were done with a 1-3/4 or 1-7/8' header. I have made enough runs to know it will not go faster than just over 108 MPH. I think my 2.5" exhaust and restrictive mufflers may be a problem. A 3000 stall brand name converter, 1-3/4" headers and flow thru mufflers is what I should try. I may be able to jet down a bit ( think its a 74 primary and 84 secondary which are factory jets for the Quick fuel 750) tire spin isn't the issue. I have the front sway bar still in, and stock front shocks, and stock springs with air shocks in the rear, which I know is not ideal, but the wider 12 bolt rear end makes the tires contact the fenders when it squats. so I do know I have weight transfer issues, but no wheel spin. The horsepower mystery, all I can think is jetting and exhaust...
 

Clipclop80

Not-quite-so-new-guy
Thread starter
Apr 9, 2021
21
3
quiet. but it seems to run well. small puff of black smoke at the start tells me I am rich on fuel...
 

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Clipclop80

Not-quite-so-new-guy
Thread starter
Apr 9, 2021
21
3
I would like to hear some opinions on what torque converter specs and brand recommendations for my build...
I want to retain fairly decent street driving ability, but more aggressive abilities for drag racing than foot braking at 2100 RPM obviously.
406 dyno sheet.jpeg
 

bracketchev1221

Royal Smart Person
Jan 18, 2018
1,021
113
I would like to hear some opinions on what torque converter specs and brand recommendations for my build...
I want to retain fairly decent street driving ability, but more aggressive abilities for drag racing than foot braking at 2100 RPM obviously.
View attachment 173392
The converter is way tight for a cam that big. You should be 35-4000 stall. That’s not saying where you’re gonna foot brake it to just allow the engine to flash quicker. And for shift point I would keep it at 62 and let the engine run back and forth over the peak. I think your exhaust may be an issue allowing the engine to get there.
 
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