max rpm

[bandit]

Went and watched my first drag race today in Union Grove, WI. Thought it was awesome. I want to get my car out there. I have been thinking about it since I got home but have been tossing around a question. I have a 1970 383, 4 speed, 410's in back. I imagine I would have to get over 100+ mph to pull any decent times but I hit pretty high rpm's fast with these 410's. 100 seems like a stretch to me. A previous owner pretty much exclusively dragged with this setup a long time ago but I am new to this. I am nervous about pushing the engine to the rpm's I think would be needed to post decent numbers and would hate to find out I pushed too much half way down the track. Any thoughts?

 

[Jeremiah]

Do you know much about the engine? Cam specs and such would help. That said if you tell us your tire diameter you could calculate a max speed/RPM.

I used to live 8 miles from that track. Drank many beers with the founder Mr. Broadway Bob. AAA towed my broken car home from out on Hwy 50 a few times too. I sure miss being that close to a race track!

 

[bandit]

I unfortunately don't know anything about the mods he might have done. I was told it was rebuilt but that is about it. The tires are 28 inch diameter.

 

[Budnicks]

your valve springs will be a big part of the limiting factor related to RPM, weak valve springs will float quicker...

your 28" tire with 4.10 gears @ 100 mph is roughly 4920 RPM, below it's limits even stock,
a stock HP 383 is good to 5800-6000 RPM {5500 RPM safely} tuned well easily "Usually" in stock trim,
@ 6000 RPM with a 28" tire & 4.10 gears that's 121 mph,
I doubt your car will do that in the 1/4 mile, unless it's really highly modified

Not knowing what you actually have, it's hard to give a real assessment on what will happen...

http://www.wallaceracing.com/Calculators.htm

 

[bandit]

Thanks for the numbers, that makes me feel better. Surprised it would not be higher. I am pushing 3500-4000 just going 65 down the road. Haven't wanted to take it onto the interstate for that reason. Very good to know these 383's can handle the rpm's though. I need to find a long deserted road to open this thing up on.

More of a generic question. I have gone into redline but never pushed a vehicle deep into it's danger zone(per tach redline) with rpms for a long period of time. Are there any signs you will hear or feel for any given car before it goes? In other words a pre alarm of sorts to say back off, you are getting too high for too long.

 

[sleepar]

Went and watched my first drag race today in Union Grove, WI. Thought it was awesome. I want to get my car out there. I have been thinking about it since I got home but have been tossing around a question. I have a 1970 383, 4 speed, 410's in back. I imagine I would have to get over 100+ mph to pull any decent times but I hit pretty high rpm's fast with these 410's. 100 seems like a stretch to me. A previous owner pretty much exclusively dragged with this setup a long time ago but I am new to this. I am nervous about pushing the engine to the rpm's I think would be needed to post decent numbers and would hate to find out I pushed too much half way down the track. Any thoughts?

Getting the car to hook up is most of it and the lights.... keep it under 5500 shift when the engine is at peak torque and horsepower around 3500(+-) start out in 2nd gear.... don't dent the dash going from 2nd to 3rd with your fist... practice makes perfect a 383 will wind up quickly because it's light rotating assembly... you could leave a 1/4 miler of rubber or hook up and go fast... it won't be so fast you'll be taching out waiting for the quarter to end... it's different when your going 100 down the highway for miles with those low gears...

- - - Updated - - -

Vibration but usually not much warnings

 

[bandit]

Thanks for the advice!! Good stuff. I do have a line lock that I just need to wire back up. That could let me spin the tires before the run and hopefully get more grip.

So start in second and just drop the clutch. What do you think for rpm before letting go at the start? 3500-4000...? Are rpms that high going to fry the clutch from a dead stop if the tires have no give? I do burnouts up there all the time but never have heated the tires first. I just don't want to break anything trying this.

 

[IQ52]

If it is a stock rebuild the bottom end is physically able to wind 7000 rpm for a brief period of time. Don't bother even trying, the valve springs will give up long before that.
If it is stock the power will drastically drop off above 5200 rpm and there is no reason to wind it above that. It may wind beyond that but shifting at a rpm higher will cause the car to run slower in the 1/4 mile .

Unless you know for sure how the engine is built, shift at 5000 and let it wind through the 1/4 mile traps whatever rpm it will reach in high gear.

Be a weenie at the beginning of your racing career or blow up the drive train on the first pass.

Macho, macho, Macho Man! I got ta be a Macho Man. Spend, spend, spend on broken parts!!!!!!!!!! I got ta be a Macho Man!

 

[383man]

What tires will you be using ? Street tires or maybe drag radials or even slicks ? That will make a difference at how high an rpm you can launch at. You will know if it spins to much you will have to come out easier. If you run a sticky tire like a slick or drag radial and you get the tires to hook then you can launch harder. If its just a basic street tire you will have to play with launch rpm so you dont spin the tires to much. Any tire spin kills et. When I ran slicks on my 340 Dart with 4.56 gears and raced it I would launch at 6000 and up as I would tach it up to about 5000 rpm as the lites came down and then put the go pedal to the floor as I let the clutch out. But I ran it hard and felt I was there to run it hard so it will either go or blow up ! But unless you have sticky tires you will have to launch much lower like around 2500 to 3000 as you will have to see what works best and you may have to actually ride the clutch a tad to launch it. Good luck , Ron

 

[bandit]

They are street tires. I am going to find a deserted country road to practice some launches. I have an old G-tech I have been wanting to play with for hp/torque measurements anyways. Just need some space.

What would you consider respectable times for a stock car on 1/4 mile.

 

[GetX'd]

Probably low 14's if it's mostly stock.

 

[sleepar]

Find a set of decent used slicks and practice at the track you will be running.... it's all about consistency... everything factors keep a note book of all the base line and changes... One day may be colder and you'll compensate by xxxxxxxxx it's a complex thing beyond the driving... then you can ask a question about xyz and someone will know better to give an answer... start a thread with all that... you will probably run in the 16's just getting dialed into it... everything UN known...
Run 14psi in the rear tires and max in the fronts