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Post Info TOPIC: Launch tuning.


- Durand -

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Launch tuning.
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What do you see good and bad in the video?

Recommended changes?

 



-- Edited by LaVelle on Thursday 12th of April 2018 07:09:26 AM

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MVI_0173 (3).MP4 (8,388.6 kb)
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'65 Pontiac Lemans 468 t400 4.10 12 bolt

Best ET  11.43 @ 117.7



- Durand -

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It seems from playing back and forth with it on pause, that it gets separation for a split second crushing the side wall and then rebounds unloading the tire.
( my son needs to remember the 1/2 speed record function on the camera )
Resulting in tire spin after about a half a turn of the tire.
I only have regular Gabriel shocks on the rear and am thinking/hoping some DA rear shocks will take care of it.
I'm probably just second guessing myself
I reset the fronts back to 90/10 from the 60/40 as in the video and have Viking DA's for the rear ordered.


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'65 Pontiac Lemans 468 t400 4.10 12 bolt

Best ET  11.43 @ 117.7

TOG



- The Other Greg -
Olympia, WA


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What was your 60'?

Did the car pull left or right?

How is your rear suspension setup? 



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The Other Greg



- Durand -

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The 60's are 1.67-1.72 with the front shocks at 90/10, and inconsistent set at 60/40.
( 5" of travel )

It goes straight even when spinning.

The rear suspension is nothing fancy.
Factory upper and lower control arms, boxed w/poly bushings including the housing ears.
Cheap $20.00 Gabriel gas charged rear shocks
Team Z weld in ARB.
If I measured correctly I have the I/C at 49" long and 10" high from the rear axle C/L.


__________________

'65 Pontiac Lemans 468 t400 4.10 12 bolt

Best ET  11.43 @ 117.7

TOG



- The Other Greg -
Olympia, WA


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Sounds like a good setup. I agree with Martin, you could be chasing track conditions. 

We are always looking for better 60's, but consistent 60's will help to win races. If you can pull less than 1.70 consistently don't mess with it. My humble 2 cents



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The Other Greg




- Jason -
Marysville, WA


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Exactly what tires are you using? Drag radials or slicks, size, compound, tire pressure.....?
What does your car weigh?
What is your torque converter stall speed?
How do you launch it? Foot brake or tans brake? What RPM do you leave the line at? Off idle and mash it or Brake stall it up a it?

My 69 Chevelle, I was running 295/65-15 BFG drag radials on 7 inch rims (because that's all I had at the time) at 16psi but should have been around 10psi.
Leaving the line at about 1200 rpms the best 60' was 1.76

Using 28X10.5 Hoosier slicks at 11psi at Pacific I got back to back 60' times that were very consistent, 1.65 and 1.66. The only other change was lower control arm relocation brackets in the first notch down.

My car setup was the same otherwise: UMI rear trailing arms, adjustable uppers, Monroe gas mag shocks all around, front sway bar connected, 1/2 tank of gas.

Something to consider, if you have a full weight car with slicks, is a stiff sidewall slick. My cousin has had good success using them on his 3000 lb 68 Dodge Dart, 512 CID with trans brake and foot brake.

Attached my Chevelle times. Wish I would have wrote the temp and DA down also, maybe next time. My specs are in signature.

Good luck with the 60s.

Jason



-- Edited by JBSS396 on Saturday 14th of April 2018 05:25:09 PM



-- Edited by JBSS396 on Saturday 14th of April 2018 05:27:42 PM

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69 Chevelle SS 
454 10.4:1, Engle HFT cam 244/260 at .050", .570 lift, 850 Mighty Demon Carb, TH 350, 10" TCI 3500, 12 Bolt 373's, 28x10.5 slicks 

Best Time at Pacific 6/20/2014, 11.96 @ 110 mph.

79 Malibu: 350 with Vortec heads, Performer Intake, Q-jet, TH350, 3.31 gears

Tow rig: 82 Chev C20 Scottsdale 454



- Durand -

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Jason,

M/T ET. Street Dot. slicks 28/11.50-15
3520 wo/driver (1980 fr 1540 r ) 3700-3720 w/driver
4500 stall
Foot brake launch. Letting it flash from high idle ( 1000 to 1200 rpm)

I've been looking into switching to Drag Radials and you are a perfect person to help me with that.
Do you still have the M/t 295/65R15's around, worn out or not for measuring?
I have been looking at the M/T 275/60R15's and 295/65R15's.
The 275's are the same size as the slicks I have now, but I'd like to go to a little taller tire but I'm not sure if the 295 will fit with wise at the sidewall pooch, and I don't trust M/T's measurements. ( never the same as the actual tire in my experience )

Durand

__________________

'65 Pontiac Lemans 468 t400 4.10 12 bolt

Best ET  11.43 @ 117.7




- Jason -
Marysville, WA


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Posts: 1431
Date:
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Hey Durand,

I have the 295/65-15 BFG drag radials mounted on 7 inch Weld wheels right now. They should be on 8 or 10s.
You are welcome to use them for test fitting or you can have the tires for cheap. Still good tread on them but they are a few years old.

With your tires and instant center you should be launching good.

Let me know about the tires.

Jason

__________________

69 Chevelle SS 
454 10.4:1, Engle HFT cam 244/260 at .050", .570 lift, 850 Mighty Demon Carb, TH 350, 10" TCI 3500, 12 Bolt 373's, 28x10.5 slicks 

Best Time at Pacific 6/20/2014, 11.96 @ 110 mph.

79 Malibu: 350 with Vortec heads, Performer Intake, Q-jet, TH350, 3.31 gears

Tow rig: 82 Chev C20 Scottsdale 454

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