Launch RPM for a 4 Speed?

CopoFan · #1 07-16-2009, 07:18 AM

So I finally got Ribbon COPO out to the strip this past weekend (first time I've ever drove a stick down the strip), and was disappointed with 4 passes all around 13.70. I was running slicks, and it has a pretty nasty bog when launching, even with the RPM's up in the mid 3000's. Tires didn't break loose at all.

I know we jetted the secondaries up at one point, and at that throttle position, the secondary accelerator pump is probably out of the picture. Timing is around 17, almost 40 at 3500 RPM. It runs fine on the street.

Its got a built 396 (11.5:1), 4 speed and 4.10 rear. My buddy did have a high 12 pass with it, and he didn't shift it too well.

I assume it just needs more RPM's at the line... but how high is safe? I'm not looking to break anything. I'd hate to damage its KQ rear.

Also, any chance of hurting anything since it has ladder bars, or do those actually help?

Thanks!

**PxTx** · #2 07-16-2009, 07:51 AM

I've got a 65 Malibu SS with a 327 and a 4 speed. It has been quite a while since I've had it at the track, but I was always of the opinion if you've got slicks- You leave at the smae RPM you shift at.

If the car is in good enough mechanical shape to race, you shouldn't break anything other than breaking into the 12's.

**markjohnson** · #3 07-16-2009, 08:37 AM

Hey, I just wanna say, is that a blast driving that 4-speed down the strip or what?! I've raced 9-second Drag Radial cars in competition but they always 'Glides or Turbo 400's. When I blasted down the strip in my 11-second '55 Chevy with the stick shift, I couldn't believe how much fun it was! It made me realize that this.......is what I've been missing from my life. A clutch pedal at the drags!

**Fast67VelleN2O** · #4 07-16-2009, 11:33 AM

My 67 Camaro, basically stock 350 with 3.42's on slicks with a 4 speed M20. I launch the car at 5,000-5,500 rpm. Dead hooks.

**Salvatore** · #5 07-16-2009, 02:58 PM

Put a little more air in the slicks and come out higher. 3000 rpm with slicks is a little low.

**sYc** · #6 07-16-2009, 05:14 PM

If worried about hurting the original rear, which is very possible leaving at 5000 or so, with slicks and a stick, I would put a set of street tires on it, which will spin when leaving, making it much easier on the RE, will allow your motor to rev (making power) and as you get used to it, you will still be able to turn some very respectable times.

Chevy454 · #7 07-16-2009, 08:05 PM

What was your MPH? That will tell the tale of how good your engine is...also, you need your timing in a lot earlier...all in by 2k would be nice. Carb stuff...Eric would be the man to talk to, the bog could be from a number of things, wrong jetting, float level, fuel slosh, etc...

Also, if you value that KQ at all, get it the heck out of there...I've seen people twist rear ends on drag radials and even street tires...rare, but it happens...you have to realize, the track is prepped to hook, so you're gonna find the weak link in your drivetrain, I promise!

**YENKO DEUCE REGISTRY** · #8 07-16-2009, 08:27 PM

[ QUOTE ]
... but it happens...you have to realize, the track is prepped to hook, so you're gonna find the weak link in your drivetrain, I promise!...

[/ QUOTE ]

Very true, just ask COPO Pete when he was testing his COPO Camaro / Chevelle / Nova for MCR 10 years ago - the rear broke in the Chevelle! It didn't hurt the tube, but like Rob says - it happens!

**markjohnson** · #9 07-16-2009, 08:31 PM

I think I remember when COPO Pete broke that Chevelle 12-bolt. If I remember correctly, the axle tube actually ripped out of the cast center section. It was an ugly picture.

CopoFan · #10 07-16-2009, 09:44 PM

Hmmm, lots of good info to digest here.

To answer a few questions... MPH was 102 - 104 every time. 60 foot time was between 2.10 and 2.20.

My brother tried one pass, launched it at 4000... and the bog was almost gone... 60 foot time was 1.90, but unfortunately, the clutch linkage came apart after shifting to 2nd gear. (the cheapest weakest link I can think of), so no idea what 1/4 mile time would have been.

I thought about going back to street tires, maybe next time out I'll give those a shot. Seems safer on the drivetrain at least. The slicks had about 13 psi in them, and i didn't bother burning out after the first time... to try and get them a little less sticky.

As for timing, I didn't realize you want the curve in that low... I always check it at 3000 - 3500 RPM. I'll have to check it at 2000... and figure out where to pick up some MSD weights and/or springs.

And thats quite frightening about COPO Pete... which is a big reason why I've been considering pulling the rear and storing it until (and if) I restore the car. I've also considered selling the KQ and using the $$$ to build a bigger motor... since the motor and trans are long gone... but I'm not ready to do that just yet.