Drag radials vs street tires.

[justcruisin]

I went to the drag strip today with some friends for a fun day put on by my local club. First time for me, they didn't have the full timer running but they gave us our et and mph. My best run was 13.02 @ 108.9mph. The track was not prepped and I was running my every day 255/50zr17 street tires and full exhaust. Couldn't get my foot to the floor until 3/4 way through first gear. Car is 71 Charger 448ci auto 3.23 and weighs in at 4050lbs. What is the potential with maybe some drag radials. By the way - I had a blast!!!

[BSB67]

Glad you had a good time.  If more people would go to the track, I think a lot of people would return to the track.

Those are respectable street car times.  I don't recall what you have done to the motor.

The 60 ft. time is what is really needed to round out the info and answer your question.  This is what we can tell: at race conditions you were making about 420 net actual flywheel horsepower.  If you tell me the track, date and time, the hp can be converted to "corrected" numbers.  If this was your first time out, there could be some driver issues that are effecting the mph ( from which hp is calculated).

For the et and 60 ft. times, the drag radial will help a lot from the times you posted.  However, with good driving technique alone (no tire change) you could get to about 12.75.  That would be about a 2.0 second 60 ft time.  If you have a stock type converter, and at that gear and weight, it will be hard to get much better than 1.8 - 1.85 second 60 time even with drag radials.  That will net you about a 12.4 or 12.50.  As converter stall gets higher, and suspension gets better, the et and 60 ft will continue to drop from there.

[justcruisin]

The motor is pretty basic, I built it around 4 years ago, it hasn't skipped a beat in that time and is plenty strong on the open road where I use it most - for me anyhow. Engine is 448 zero deck short block, ootb eddy rpm's and rpm intake, comp xe275hl, 1 7/8" headers. Converter is an 11", I can foot brake it to around 2800. My 60ft times will be down I'm sure, every car I raced bar one pulled a lead on me off the line, most were on street tires. the competition wasn't stiff and I actually didn't loose a race. I imagine my driving skill - or lack of, would be a big factor in how the car leaves the line. How much could this effect my mph? I have a rev-n-nator control and set the limiter to 5500 and was shifting just below that. ET's ranged from 13.61 - 13.02 and MPH was low 106's to 108.9.

One of the track guys spoke to me after the day and told me I needed more heat in my tires, I only did a 2-3 sec burn out as i didn't think there was any point with street tires?

I live in New Zealand so I don't think you will have info on the track. The track is Meremere - Fram dragway and is about sea level, the temp for the day was around 65F.

[firefighter3931]

Drag radials will make a big difference. The softer compound will allow the car to hook much better. It all starts with the launch   

You have enough trap speed for mid 12's so work on the launch and your ET's will drop. 

Nice job....a day at the track is allways a fun day 



Ron

[BSB67]

I imagine my driving skill - or lack of, would be a big factor in how the car leaves the line. How much could this effect my mph? I have a rev-n-nator control and set the limiter to 5500 and was shifting just below that.

One of the track guys spoke to me after the day and told me I needed more heat in my tires, I only did a 2-3 sec burn out as i didn't think there was any point with street tires?

How the car leaves the line will not have a measurable impact on the mph, only et.  Horsepower, weight and mph are related.  You can influence the mph a little with other items, such as rotating weight, reduction of parasitic losses, but generally the mph/hp/weight hold steady.  Shift point is about the only thing that will effect mph of the car if everything else is okay.  If your valve train is stable, I would think it would respond well to 5800 shift point, maybe higher.  The only way to know for sure is to try it.

There might be some gain in tire stick with a better burnout, but if you have crazy wheel spin, you will get more from better launch technique.

[justcruisin]

OK, thanks for the input, some things to work on - that's good. The car seems to be pulling well at 5500 so I will set my limiter to 6000 and see how I go. I have PRW stainless roller tip rockers with 3/8 push rods so i guess that will be good to 5800 but the tests I have seen on that cam seem to fall off around 53-5400, but definitely worth a try.

I think a set of drag radials will be on my shopping list, realistically I'm gong to have the opportunity to go to the track around 4 times a year so I think my skills will need all the help they can get. I am also considering a new complete pumpkin with a 3.91 cog from DR Diff so I can swap it out when needed.

                   

[BSB67]

OK, thanks for the input, some things to work on - that's good. The car seems to be pulling well at 5500 so I will set my limiter to 6000 and see how I go. I have PRW stainless roller tip rockers with 3/8 push rods so i guess that will be good to 5800 but the tests I have seen on that cam seem to fall off around 53-5400, but definitely worth a try.

I think a set of drag radials will be on my shopping list, realistically I'm gong to have the opportunity to go to the track around 4 times a year so I think my skills will need all the help they can get. I am also considering a new complete pumpkin with a 3.91 cog from DR Diff so I can swap it out when needed.
                   

Cam power peak probably 5400, but should carry another 400 to 600 rpm to maximize the area under the curve.....if the valve train is capable.