If all goes according to plan, and with the nice weather predicted for the weekend, we're going to take 2 cars down for some drag racing at Cedar Falls.
Jenna is running her G8 (her first time ever drag racing), and I'll be running my Chevelle.
Anyone else interested in going?
Derek69SS said
Oct 29, 2020
56° with a 20mph tailwind... Good weather for new bests!
Hoping to run a 11.9 with the Chevelle, and a 12.9 with the G8.
Expecting to be a tenth or two slower in both cars.
-- Edited by Derek69SS on Thursday 29th of October 2020 03:40:28 PM
BLyke said
Oct 29, 2020
Hope it goes well for both cars, looking forward to seeing the results!
Derek69SS said
Oct 31, 2020
Chevelle went 12.210 @ 115
G8 went 13.003 @ 109
Derek69SS said
Nov 2, 2020
So I'm now trying to figure out how much money to throw at the Chevelle again.
Online calculator shows: 3700lb Chevelle w/driver going 115 trap speed is making 439hp at the wheels 4150lb G8 w/driver going 109 trap speed is making 419hp at the wheels
Those numbers might be a little inflated due to tailwind, but they're not too far off. The most shocking part is that she's within 20rwhp of me with stock exhaust manifolds, cats, full factory exhaust (except the tailpipes), 5 mufflers, stock intake, 20 less cubic inches, and through an automatic!?!? The G8 has better heads, bigger bore, and shorter stroke. Both cars have the exact same cam.
I probably should be happy with 439hp at the wheels from 383 cubic inches... but I'm not.
Derek69SS said
Nov 2, 2020
Video of 12.210 pass...
Lost in the 60s said
Nov 11, 2020
Watching the vid, you are shifting rather slowly and carefully, to not miss a gear. I believe, if you were speed shifting, the et would have been lower and the calculator may have come up with a higher hp estimate. The trap speed seems low for the et too. My best time with my old '70 SS was 12.65 with a 118 trap speed with 3.73 gears. My gear ratio may account for the higher speed with a slower et and that was in 3rd gear. No room to pick up forth. Maybe you could have grabbed 1 more gear and raised the trap speed ? The calculator only takes into account the numbers and not all the variables. Running almost a full second faster than the G8 one would certainly expect your engine to be producing a fair amount more hp... and Jenna had the advantage of the automatic "speed" shifting for her. Get the Chevelle on a chassis dyno next year and you may have a different outcome and possibly, a more accurate estimate of rwhp What is really hard to believe is the et for the G8. I remember the days when a 13 second street car cost a LOT of money to modify and the G8 damn near went into the high 12's. Over 400 rear wheel hp on a street sedan ?? Obviously, 50 years of engine technology has drastically changed the game.
Derek69SS said
Nov 11, 2020
I need to shim my clutch slave cylinder so I can shift faster. That's about as fast as I can shift it as it is now, since the pedal needs to go nearly to the floor before it'll go into the next gear. Pulling the trans is kind of a big ordeal on this, since I didn't provide enough tunnel clearance to do it easily. I put it off for a year already, but it has to be done now because the rear main seal has started leaking. I'm hoping with a properly shimmed slave, I'll be able to stay on the power while shifting too. My car has been on 2 chassis dynos. Dyno numbers can vary quite a bit. One said 404hp, the other was 434hp. 439 calculated seems pretty accurate, considering the cooler weather.
The G8 still has a stock torque-converter and 2.92 rear gears, which is killing its 60' times. Even on drag radials, I couldn't get it under 2.0. That car with a better converter and a 3.45 Camaro differential swap should go 12.50s pretty easily. After a month with the cam swap and tune, she's already burned off a pair of rear tires, so I'm not sure how much faster I want to make it.
After giving it some thought, her tight converter and 2.92s behind an automatic probably isn't robbing much if any more horsepower than my manual through a 9" with 4.11s. I might have picked up some mph by grabbing 5th also since I was trapping at 6000rpm but peak power is at 5650, but figured I'd be slower ET with another shift. I think the horsepower difference between the two all comes down to exhaust. I'm getting everything I can out of the cam I have, and hers is almost there just choked a bit with manifolds. (same cam in both cars).
There's another 50hp in my car on the top end with a bigger cam. I'll lose a little on the bottom, of course though.
Lost in the 60s said
Nov 11, 2020
I was wondering if the hydraulic clutch was slowing down the shifting. Have you ever tried just lifting and dropping your right foot while yanking the lever without the clutch ? It's cool when it works, but is a bit hard on the engine when it doesn't. With your rev limiter, it would prevent over revving, where my LS 5/6 engines sometimes bent push rods for me to change in the pit. I always carried extras, even on the street for missed shifts. Rocker arms too, as a few times, the 7,500 rpm drove the push rods right thru the stock arm...
Derek69SS said
Nov 12, 2020
I've never tried shifting it without the clutch
I think the majority of the problem will be fixed by shimming the slave, but I'm also adding a remote bleeder while it's out.
Lost in the 60s said
Nov 12, 2020
That will be cool if it gets better with the shim. My rollback has a hydraulic slave to fork set up and needed replacement. There is NO bleeder on the slave. All the air needs to work it's way up the hose to the reservoir on the firewall ?? What the heck ? I bled it some by leaving the hose loose, but it still took a while for it to work properly and I could stop topping off the fluid.
Back in Black said
Nov 15, 2020
Derek69SS wrote:
I've never tried shifting it without the clutch
Try it, you'll like it!
Derek69SS said
Nov 16, 2020
That's cheating Keith!
Looks like fun.
Lost in the 60s said
Nov 16, 2020
What is that ?? some kind of ratchet shifter that cuts the ignition when you yank it ?
Anyone else have the subject title disappear on a reply page ? It keep getting the message that the title is too short and all that is in that line is "RE" ??? I have to type in the thread name.
Back in Black said
Nov 16, 2020
Lost in the 60s wrote:
What is that ?? some kind of ratchet shifter that cuts the ignition when you yank it ?
Anyone else have the subject title disappear on a reply page ? It keep getting the message that the title is too short and all that is in that line is "RE" ??? I have to type in the thread name.
Dog gears shifted sequentially. There is a strain gauge in the shifter linkage that sends an ignition cut signal to the computer. The ignition cut takes the load off the dogs enough to disengage them and shift into the next gear.
Back in Black said
Nov 16, 2020
Derek69SS wrote:
That's cheating Keith!
Looks like fun.
Lost in the 60s said
Nov 16, 2020
Back in Black wrote:
Lost in the 60s wrote:
What is that ?? some kind of ratchet shifter that cuts the ignition when you yank it ?
Anyone else have the subject title disappear on a reply page ? It keep getting the message that the title is too short and all that is in that line is "RE" ??? I have to type in the thread name.
Dog gears shifted sequentially. There is a strain gauge in the shifter linkage that sends an ignition cut signal to the computer. The ignition cut takes the load off the dogs enough to disengage them and shift into the next gear.
I could hear the engine cut out, so figured it worked together with the shifter movement. Very techie and cool.
None of my cars have a computer to do that with. My right foot was my computer way back when.
If all goes according to plan, and with the nice weather predicted for the weekend, we're going to take 2 cars down for some drag racing at Cedar Falls.
Jenna is running her G8 (her first time ever drag racing), and I'll be running my Chevelle.
Anyone else interested in going?
56° with a 20mph tailwind... Good weather for new bests!
Hoping to run a 11.9 with the Chevelle, and a 12.9 with the G8.
Expecting to be a tenth or two slower in both cars.
-- Edited by Derek69SS on Thursday 29th of October 2020 03:40:28 PM
Hope it goes well for both cars, looking forward to seeing the results!
Chevelle went 12.210 @ 115
G8 went 13.003 @ 109
So I'm now trying to figure out how much money to throw at the Chevelle again.
The G8 has better heads, bigger bore, and shorter stroke. Both cars have the exact same cam.
Online calculator shows:
3700lb Chevelle w/driver going 115 trap speed is making 439hp at the wheels
4150lb G8 w/driver going 109 trap speed is making 419hp at the wheels
Those numbers might be a little inflated due to tailwind, but they're not too far off. The most shocking part is that she's within 20rwhp of me with stock exhaust manifolds, cats, full factory exhaust (except the tailpipes), 5 mufflers, stock intake, 20 less cubic inches, and through an automatic!?!?
I probably should be happy with 439hp at the wheels from 383 cubic inches... but I'm not.
Video of 12.210 pass...
Watching the vid, you are shifting rather slowly and carefully, to not miss a gear. I believe, if you were speed shifting, the et would have been lower and the calculator may have come up with a higher hp estimate. The trap speed seems low for the et too. My best time with my old '70 SS was 12.65 with a 118 trap speed with 3.73 gears. My gear ratio may account for the higher speed with a slower et and that was in 3rd gear. No room to pick up forth. Maybe you could have grabbed 1 more gear and raised the trap speed ? The calculator only takes into account the numbers and not all the variables. Running almost a full second faster than the G8 one would certainly expect your engine to be producing a fair amount more hp... and Jenna had the advantage of the automatic "speed" shifting for her. Get the Chevelle on a chassis dyno next year and you may have a different outcome and possibly, a more accurate estimate of rwhp What is really hard to believe is the et for the G8. I remember the days when a 13 second street car cost a LOT of money to modify and the G8 damn near went into the high 12's. Over 400 rear wheel hp on a street sedan ?? Obviously, 50 years of engine technology has drastically changed the game.
I need to shim my clutch slave cylinder so I can shift faster. That's about as fast as I can shift it as it is now, since the pedal needs to go nearly to the floor before it'll go into the next gear. Pulling the trans is kind of a big ordeal on this, since I didn't provide enough tunnel clearance to do it easily. I put it off for a year already, but it has to be done now because the rear main seal has started leaking. I'm hoping with a properly shimmed slave, I'll be able to stay on the power while shifting too.
My car has been on 2 chassis dynos. Dyno numbers can vary quite a bit. One said 404hp, the other was 434hp. 439 calculated seems pretty accurate, considering the cooler weather.
The G8 still has a stock torque-converter and 2.92 rear gears, which is killing its 60' times.
Even on drag radials, I couldn't get it under 2.0. That car with a better converter and a 3.45 Camaro differential swap should go 12.50s pretty easily. After a month with the cam swap and tune, she's already burned off a pair of rear tires, so I'm not sure how much faster I want to make it.
After giving it some thought, her tight converter and 2.92s behind an automatic probably isn't robbing much if any more horsepower than my manual through a 9" with 4.11s. I might have picked up some mph by grabbing 5th also since I was trapping at 6000rpm but peak power is at 5650, but figured I'd be slower ET with another shift. I think the horsepower difference between the two all comes down to exhaust. I'm getting everything I can out of the cam I have, and hers is almost there just choked a bit with manifolds. (same cam in both cars).
There's another 50hp in my car on the top end with a bigger cam. I'll lose a little on the bottom, of course though.
I was wondering if the hydraulic clutch was slowing down the shifting. Have you ever tried just lifting and dropping your right foot while yanking the lever without the clutch ? It's cool when it works, but is a bit hard on the engine when it doesn't. With your rev limiter, it would prevent over revving, where my LS 5/6 engines sometimes bent push rods for me to change in the pit. I always carried extras, even on the street for missed shifts. Rocker arms too, as a few times, the 7,500 rpm drove the push rods right thru the stock arm...
I've never tried shifting it without the clutch
I think the majority of the problem will be fixed by shimming the slave, but I'm also adding a remote bleeder while it's out.
That will be cool if it gets better with the shim. My rollback has a hydraulic slave to fork set up and needed replacement. There is NO bleeder on the slave. All the air needs to work it's way up the hose to the reservoir on the firewall ?? What the heck ? I bled it some by leaving the hose loose, but it still took a while for it to work properly and I could stop topping off the fluid.
Try it, you'll like it!
That's cheating Keith!
Looks like fun.
What is that ?? some kind of ratchet shifter that cuts the ignition when you yank it ?
Anyone else have the subject title disappear on a reply page ? It keep getting the message that the title is too short and all that is in that line is "RE" ??? I have to type in the thread name.
Dog gears shifted sequentially. There is a strain gauge in the shifter linkage that sends an ignition cut signal to the computer. The ignition cut takes the load off the dogs enough to disengage them and shift into the next gear.
I could hear the engine cut out, so figured it worked together with the shifter movement. Very techie and cool.
None of my cars have a computer to do that with. My right foot was my computer way back when.