Launch RPM for a 4 Speed?

[Mr BB Chevy]

my street car

atco early 1980's

5800-6000RPM launch 11.22's 110-118mph


Im re-doing my chevelle now keeping it as a day2 car.
M&W bars, tow tabs, mechanical tach etc.


newest add-on from ebay...

[PxTx]

I've been running the same shifter on my 65 for a long time and LOVE it. It looks so good poking through the factory consol. Yours looks a lot more modern than mine. Do you know much about yours?

[CopoFan]

69L34M20: I agree... I think the motor has a bit more... its never been properly tuned since it was built 10 years ago... its got about 1000 miles on it. Good point about the c-clips, that would totally suck to have one fail, and its happened to me already, at least it was an 81 Park Avenue and not a fun car like this.

The cam is a Comp Cam solid lifter 294 duration (248 @ .050) 0.595 lift solid lifter with roller rockers. Compression is a blueprinted 11.4 : 1, and it was bored .030 over. Intake is an Edelbrock Performer RPM, 750 Holley Double Pumper, and MSD ignition.

goinforbroke: I've never heard of that calc... but it sure seems pretty accurate... I tried it on a few buddies' car from Sunday and its pretty close for them all.

Rob: I'd be happy to run mid to high 12's consistantly, I know I don't have the cubes to hit the lower 12's with the weight. I'm hoping some tuning brings the MPH up a bit.

sc69sam: While I'm not going out every weekend, I love to take a car out a few times a year to have some fun. There is no street where I can open it up like the dragstrip.

mfchassisworks: Good question on the fuel pressure, its a holley mechanical pump and its pulling 6 psi at idle, but no idea under load. Awesome explanation on the "bog", my gut feeling was that I can't get big enough jets or enough timing to compensate for the "bog", it seemed like the only cure is RPM.

Mr BB Chevy: AWESOME picture!!! As much as that kind of launch would scare me... I'd brag about that picture for the rest of my life! What kind of motor were you running back then?

And one final kind of dumb question for all of you...

How do you watch your RPM's on the line, trying to keep them over 4000, while watching the tree? Its hard to go by sound when the car in the other lane is louder than yours. I think part of my problem was I was letting off a bit without realizing it as the lights ticked down.

And finally, you guys are all awesome, never expected this kind of response for a somewhat generic question!!!

[mfchassisworks]

Awesome pic MR BB CHEVY!!

If you dont want to run a fuel pressure gauge make a temporary T-fitting install it as close to the carb as you can, get Autometer's copper oil pressure line, and get a small liquid filled gauage and install in on the end of the line. Run it up the cowl to the base of the windshield, under a wiper arm, or 200 mph tape it to the windshield where you can see it. Find a safe place to run through the gears, Then watch how low your fuel psi gets. You will be surprised. If you don't have always have 7psi then you aren't making hp. If you try to tune based off you plugs at the end of a run they will give you a false reading as the carb will seem lean but really there simply isn't enough fuel. No fuel means low hp = low mph.

For the launch don't worry about the other guy, when you are testing there is no prize for cutting a good light. Let the other guy leave first then watch your tach and go. Keep raising the RPM of the launch until the bog goes away. and...hold on!!

[Stitch]

This was my street car from the early 80's , small block , 4 speed , 5.13:1 rear . Launched around 5800 - 6000rpm

[70 ls6 convert]

i pulled my 70 chevelle ls5 4speed out of 10 year storage to race at an abandend runway,been dumping the clutch at about 28oo,there aint nothen funner then racing a 4speed big block..https://www.youtube.com/watch?v=mKs4F9RDqrE