[67_LS1]

I’ve been following a thread on here about running 11’s with 2.56 gears. Very interesting how all of the racers on here guesstimate performance but they all seem to use a lot of data in their decision processes.

Project: Run 11s with 2.56 gears, factory converter, and...

If you need one more dyno and drag test to look forward to... 1970 MC 4110 lbs Original TH350 and converter Locked, 2.56 12-bolt Current 467 (estimated 450-460 hp) showing about 380 hp running 13.0 @ 108 mph, best 60’ 1.98. In case you’re wondering about the disparity between max hp and hp...

www.chevelles.com

Which got me curious so I started looking at online drag race calculators and the only thing I’ve been able to find only asks for weight and HP. Doesn’t seem possible.
To prove to myself that something is missing I put in my data; 3400 lbs with me in the car and 325 crankshaft HP and it gave me an ET of 13.24.
It didn’t ask at what RPM the HP was at, transmission ratios, rear gear ratio, tire size. Doesn’t this seem odd?
Does anyone know of a better one?
I know, I know, I should go to the track and run it to be sure. I will try to make the Wednesday Night Drags at Sonoma Raceway in late August when my grandson is here. But until then?

 

[PileDriver]

The Wallace site with a lot of the popular calculators is pretty accurate for an optimized combo.

When it comes to drag racing ETs, how you use your power for the first 330' is everything. The 60', the 1-2 shift rpm, the suspension, all work together to whittle that time quicker and quicker.

That being said, a car that is "close" to correct will run well. For the average joe with an 11 second and slower street/strip car some basics like a good 3500-4000 converter, 3.50 to 4.56 gear, and everything tuned correctly will run a number that'll fall short of the online calculator equation but be fairly close. Its those last few tenths that cost the bucks and the effort!

 

[67_LS1]

Thanks. I went to Wallaceracing.com and they did have a calculator that at least adied rear ratio, tire diameter and how many shifts To the weight and HP question.
Good news is I knocked a 1/2 second off my imaginary ET !
Which is kinda my point. I seriously doubt my V6 powered Chevelle with 3.07 gears is going to rip off a 12.7 ET.

 

[-SS454-]

I don't put a whole lot of stock in those online calculators. The ones going over engine power do not accurately calculate driveline losses. Weather and altitude aren't really factored in. As for the 1/4 mile, too many variables. I'd put more belief in the MPH than the ET.

 

[smitty454]

Yep way too many variables for a calculator. You can have 600hp but if you dont hook it you are going to run a 13 sec 1/4 mile.

It will be interesting to see what yours runs with that modern 6 cylinder.

 

[67_LS1]

Yep way too many variables for a calculator. You can have 600hp but if you dont hook it you are going to run a 13 sec 1/4 mile.

It will be interesting to see what yours runs with that modern 6 cylinder.

If I can find a calculator that’s puts me in the 9’s, I may never run it.

 

[shovelrick]

I have a full weight plus some 68 with a 590 hp 600 tq engine with a T400 and 3.73 gears but haven't been on an drag strip strip (1-2 times) since the late 70's, if I used a calculator that said 14's or slower might be right lol, only real way IMHO is to get on the drag strip, JMHO

 

[77 cruiser]

This one is pretty close, just does MPH.

 

[jeff swisher]

I have played with the calculators and with a good launch they are pretty close.
With a poor launch they can be way off like stated.

I had a fairly light 78 Nova 3000 lbs with driver.
I had 3.08 gears in a 10 bolt and it ran 14.5's best et, not spinning.
I swapped to a Ford 9" with 3.70 gears and it went 13.7's
My heavier 57 chevy 3800+ lbs with nearly the same sbc did not change much more than a tenth with the same gear change.
A converter change really helped it 2500 to a 4500 stall

 

[billdini]

In car electronic units using GPS and G sensors it can accurately calculate your HP and torque as well as time and speed if you provide an accurate weight. However once tire spin is in the equation things must go inaccurate at least for a while.

 

[68Chevele]

I don't use any calculators, I go to the track and see what the car runs. They always give me a time slip that makes me happy.

 

[Derek69SS]

Calculators are for optimized combination, and good launch... consider those the best your HP and weight might be capable of if everything else is perfect.

 

[billdini]

The one in my Shelby was dead on accurate. I could try different launch control settings, shift points, tune specs and see the results immediately. Problem with that car was finding a road that is straight and safe as possible because that car did pretty close to 140mph in the quarter when all set up. In Fl not to hard up here it was impossible and never did it up here.