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I have a 468 in my 70 backed by a TKX wide ratio going through a 3.08 rear. with the 3.27 first gear in the trans and the 3.08 rear it launches hard through the gears. Since its a new build I have yet to push it hard as I believe the drivetrain will suffer. Mark Jones built the motor and it has over 550 both on torque and HP. With the overdrive it cruises at 70 mph at only 2200 rpm.
I do have coilovers at all four corners as well as most Vansteel suspension upgrades.
I was worried about the wide ratio trans but Jeff at Silversport highly recommended the wide ratio and it has worked out just fine.
Long live the big block
Thanks Leon!
Yep I almost afraid to try to get a great launch / 60ft !!
Maybe it will survive a couple...I hope.
Bucaneer
1.60s are fabulous!
Any diff issues?
At 500 HP mine should do low 12s on street tires. With suspect traction.
At near 115mph. Several similar builds have. ~ High 11s if it hooks.
I know I left 100HP on the table.
I am using the ancient L88 heads with their awful round exhaust port.
Modern AFRs and a Wilson ported intake virtually guarantee me 580HP.
Just a few bolts away! LOL
That might mean 120mph trap speeds and mid to low 11s if it hooks.
But all the improvement with the AFRs & intake is all past 4000rpm, and I just didn't care.
I wanted the L88 snowflake heads more, they are much more period correct.
It will drive the same, either way.
And be way different than my LT-1. NO WAITING!
I am sure I will lose 1/2 sec to 1 sec with a soft launch, that's OK, I'd rather the IRS live.
I will no longer have to wait for the rpms to build for sure!
Last edited by leigh1322; Apr 14, 2025 at 05:36 PM.
Yep I almost afraid to try to get a great launch / 60ft !!
Maybe it will survive a couple...I hope.
Bucaneer
1.60s are fabulous!
Any diff issues?
My original 'technique' with the 3.08 rear/2.20 1st gear of the M21 was to pull away off the line with a 'light' gas pedal to avoid wheelspin for the first 20 yards or so.....then hit the gas pedal hard, bring the front up high, shifting into 2nd at about 6000rpm just past rpm peak, and again into 3rd at similar rpm........its only then in the higher double figure speeds that front-end settled-down and rear end 'relaxed' and the very real risk of rear-end 'stepping-out' if the road surface was the slightest bit slippery.......
Even though the car isn't a quarter miler it does make me wonder whether to consider alternative dampers (to the current KYB's) and 'sticky' rear drag tyres........but how will that effect general handling?
I will be going adjustable dampners for their tuneability.
That way I get get the best compromise between handling, or traction, or ride.
Or have 3 different settings.
I have single adj already.
Thinking of going to doubles before I even put them on.
I have several stock LS6's in my database at 12.1 to 12.6 @ 112-114.
One was the Car Craft car from 1971.
A few on slicks at 11.75, 11.90 to 12.30 @ 114.
With AFRs it equals the power of an L88 which ran 11.88 @ 121.
Low 11s should be possible with that.
All stock cammed engines.
An LS6 drives much better than an L88 with the much milder cam, more cubes, and roughly 100# more TQ at 2500 rpm.
Shocks:
On the shocks, much of the handling improvement comes from tighter rebound settings.
Tightening up compression too much can make it "skip". Street level compression is OK.
For a drag launch, you want looser rebound in the front. And tight compression so it does not come down.
And very tight compression in the rear. So it doesn't sag. And likely rebound too.
For ride you focus primarily on compression, and need it as soft as you can get it before the car wallows.
A little more rebound can stop the wallow, with a soft compression.
That means a good three way compromise would be tough.
Last edited by leigh1322; Apr 14, 2025 at 06:15 PM.
You know you're starting to cook when the speedo moves like a tach. It always makes me laugh watching it lol
When accelerating hard through the gears I never have the chance to look at the speedo or rev counter.........far too busy making sure I'm going in the direction intended to even have the time to glance down at either.......simply rely on the shifter indicator and rev limiter.
When accelerating hard through the gears I never have the chance to look at the speedo or rev counter.........far too busy making sure I'm going in the direction intended to even have the time to glance down at either.......simply rely on the shifter indicator and rev limiter.
It's tough on C3s, but it's hilarious on cars with a sweep style speedo. Watching it move from left to right in a blink always makes me laugh
Rosco you got me thinking about the softer traction oriented suspension:
My LT-1 (top) and your BB (2nd) actually had similar total TQ in 1st & 2nd due to gearing differences, but mine did not stick in first cause it was autocross stiff, where yours did stick cause when it had lift, and spun when stiffer.
But with the deep 1st gear of my TKX, I think it's hopeless in first gear W.O.T. no matter what!
Even 2nd gear til 75mph will be bad if I keep it stiff.
Just like Dawsons.
Oh well.
Maybe I can tune the shocks to get it to stick in 2nd, past 50mph!!
DDawson has even more TQ in 2nd (~3900), with his gearing, and his comment was it "struggles" in 2nd on good street tires.
I guess that is where I'll be.
Our deeper 1st gears, and rear gears, than Rosco, put 1st gear well past the will hook up stage, in first gear, at WOT.
But they do make it more lively at half throttle.
I have a buddy George with 411s, a TKX, and a 427, so an awful lot of first gear, and it drives great at half throttle. Never saw it a WOT.
Thank you for the driving feedback guys!
I doubt I will ever have to wait for 35+mph for the power to "show-up" any more!
Leigh you've started me off on a search. The idea of double adjustable shockers (so compression and rebound) makes a whole lot of sense. Its kinda strange that I was using some knackered-out shockers on my car which in fact gave a clue as to perhaps which direction (other than tyre selection) I should go for improved rear-end grip.
I don't want to be crawling under the car at the drags or perhaps a hill climb to make change........it isn't the the kinda thing you can do when waiting at a set of traffic lights when you've pulled-up beside another car who obviously wants to do some stoplight racing.
So......we have late model Vettes and other car with adjustable damping/suspension etc. We have systems on some of the more exotic sports cars that lower the suspension. Unfortunately perhaps not backwards compatible with C3 Corvettes. There are aftermarket electronically operated lowerable coil-overs available for a number of Japanese and European performance cars. Ideally some form of in-cabin controller connected to the shock adjusters would be ideal. Gonna see if anything is 'out there' at a sensible price.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Originally Posted by leigh1322
Thanks Leon!
Yep I almost afraid to try to get a great launch / 60ft !!
Maybe it will survive a couple...I hope.
Bucaneer
1.60s are fabulous!
Any diff issues?
At 500 HP mine should do low 12s on street tires. With suspect traction.
At near 115mph. Several similar builds have. ~ High 11s if it hooks.
I know I left 100HP on the table.
I am using the ancient L88 heads with their awful round exhaust port.
Modern AFRs and a Wilson ported intake virtually guarantee me 580HP.
Just a few bolts away! LOL
That might mean 120mph trap speeds and mid to low 11s if it hooks.
But all the improvement with the AFRs & intake is all past 4000rpm, and I just didn't care.
I wanted the L88 snowflake heads more, they are much more period correct.
It will drive the same, either way.
And be way different than my LT-1. NO WAITING!
I am sure I will lose 1/2 sec to 1 sec with a soft launch, that's OK, I'd rather the IRS live.
I will no longer have to wait for the rpms to build for sure!
SORRY! I made a typo in my post. It should have read and now corrected 1.70 60' which is still good and my hope is to get a 1.60 60' and that should put me into the 11s with NA CFI and my goal is 11.99. If I don't make it into 11s, I will know what I need to do to get me there. As far as diff issues, not yet, but every time I launch it, I'm crossing my fingers that that D44 holds together. I may do the cast iron diff upgrade like Gary always tells me to do, but I've been putting it off. Thanks for finding my mistake.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Originally Posted by roscobbc
My original 'technique' with the 3.08 rear/2.20 1st gear of the M21 was to pull away off the line with a 'light' gas pedal to avoid wheelspin for the first 20 yards or so.....then hit the gas pedal hard, bring the front up high, shifting into 2nd at about 6000rpm just past rpm peak, and again into 3rd at similar rpm........its only then in the higher double figure speeds that front-end settled-down and rear end 'relaxed' and the very real risk of rear-end 'stepping-out' if the road surface was the slightest bit slippery.......
Even though the car isn't a quarter miler it does make me wonder whether to consider alternative dampers (to the current KYB's) and 'sticky' rear drag tyres........but how will that effect general handling?
LOL, on my 69 Z, I ran slicks back then at the track and would come out of the bottom at around 5-5500, shift at 8k and that 302 would launch like a bat outta hell when hooked. I used to run at Milan Dragway in Milan MI. back then. Trailer the car since I always thought I would break something and that would be a VERY expensive tow home to OH.
I may do the cast iron diff upgrade like Gary always tells me to do, but I've been putting it off. Thanks for finding my mistake. 
