1/4 mi ET for given MPH

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mopowers

mopowers

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I understand there are TONS of variables but generally speaking, what would be a decent 1/4 mile ET for a street car that resulted in a 107 MPH trap speed?

I finally got my 68 Dart street car out to the track for the first time. I couldn’t lean on the converter much without blowing the tires off (tires are 275/60/15 cooper cobras). The best 60’ I could manage was a 1.97. Obviously there’s still a ton of tuning to be done. I’m just wondering what sort of ET you guys think would be respectable for a 107mph pass.

Also, what type of ET gains could be had with a tire that actually hooks?
 
This is from wallace. Usually pretty good.

60 Foot 1.72
330 Foot 4.97
660 Foot 7.81
660 MPH 86.99
1000 Foot 10.28
1/4 Mile ET 12.38
1/4 Mile MPH 107

I'd guess with the 60' in the high 1.9's it ran somehere around 13.3-13.5
 
i would guess you ran a 12.70. I would say you should be around 12.20's at 107
 
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Put 6 cyl bars or drag bars .810 in it and 90-10 shocks disconnect the sway bar if you have one and see if it helps the 60 ft times, I bet it will knock .3 or more off your 60 ft times and your ET, also try a adj pinion snubber against the floor. 0 - .5" gap,
I ran mine against the floor with 0 gap for drag racing it worked very well, and I ran street tires and slicks the difference was minor but the slicks were taller.

also it wont hook if you don't have weight tranfer, bars and shocks will make it hook.
 
These times are when I first started tuning my 340. Today it will 1.66 60' and run 12.0@110+ one change and take note of what works and you should be able to get 1/2 second quicker with very little money. Sticky tires and driveshaft loop are a must.
60' 330' 1/8ET 1/8MPH 1/4ET 1/4 MPH AFR DA Ft Temp
1.763 5.144 7.977 86.22 12.55 107.38 12.8 512 66.1
1.727 5.079 7.898 86.61 12.453 107.98 12.8 476 65.5
1.709 5.058 7.886 86.15 12.46 107.2 12.8 292 62.5
 
My old dart sport with a factory 89 360 with a cam would run 13.20 at 105. I think the best 60 foot was only 1.88 but that was over 10 years ago and My CRS gets worse every year. Lol
 
my Wallace numbers are slightly different>
60 Foot E.T. : 1.74
1/8 Mile E.T. : 7.88
1/8 Mile Trap Speed : 86.27
1/4 Mile E.T. : 12.49
1/4 Mile Trap Speed : 107
thats with a guess of the weight @3350lbs and 340fwhp.
Personally I think 12.20's@107 is getting a bit ahead on the ET part unless you got "stocker" spec verters/gears.

My 3580lbs all steel '71 340 cuda with stock heads, solid cam, HS dominator int, 850DP, race hdrs, 4.30's/10x28's/4200stall would run 12.41'[email protected] and it would hook with a wheel up on every run, can't remember the 60's...back in 1986.
 
Thanks for the input guys. The best ET I could pull was 12.92, but that was a bit slower at 105.6 mph. After playing with timing a bit, I was able to get the mph to 107. I think there still a tad more power in it as I didn't have time to play with jetting at all and the AFR seemed a bit fat (12.3). I also didn't play with shift points, leave rpm, etc.

I was really just using the track time as a dyno. Hopefully I can get back soon to play with the carb a bit.

As far as ET, I'm not looking for perfection with the combo since the car is 99% street driven. If I can get 12.60's out of it, that would exceed my expectations. I'll be curious to see if I can get there with the current street tires. I'll probably try a pinion snubber since I can make one for free.

Thanks again for the input.
 
The difference at your 12.92 is all in the 60'

If you get .1 out of the 60's, it's usually good for .2 at the stripe.

This is the 340 with RHS X heads, 230/550 cam IIRC. Pretty solid runs. Similar to the the demon 360,268H, J headed deal for MPH so far. I bet there is more MPH in as the cam is much larger.

I bet it would like shifts at 6K maybe a bit higher.
 
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I've raced on street tires alot, never had drag radials, lower air pressure and no water burn out, just chirp the tires and line up. And watch other cars to see which lane has the bite. Sounds like it already hauls
 
crackedback said:
The difference at your 12.92 is all in the 60'

If you get .1 out of the 60's, it's usually good for .2 at the stripe.

This is the 340 with RHS X heads, 230/550 cam IIRC. Pretty solid runs. Similar to the the demon 360,268H, J headed deal for MPH so far. I bet there is more MPH in as the cam is much larger.

I bet it would like shifts at 6K maybe a bit higher.
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Exactly. It's the 340, RHS heads, 231/561 HFT. I ran it with the 750DP. I was going to try the Proform 650, but figured I'd see what I can get outta the 4779 first. I really like this old carb. Hopefully, there's a little more power in it. I'd be happy with 108mph- just gonna take a little testing to get there.

I ended up shifting at 6500. I'll try lower next time as well.

If I could get the 60' down near 1.80, I'd consider that a victory.

Oh geez, I feel like this is a snowball... lol
 
B'cuda said:
I've raced on street tires alot, never had drag radials, lower air pressure and no water burn out, just chirp the tires and line up. And watch other cars to see which lane has the bite. Sounds like it already hauls
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How much air pressure do you run in your street tires at the track? I just ran the 30lbs I drove to the track with. LOL

I was able to upload a video from my quickest ET. I was subsequently able to add 1mph with less total timing.

 
mopowers said:
How much air pressure do you run in your street tires at the track? I just ran the 30lbs I drove to the track with. LOL

I was able to upload a video from my quickest ET. I was subsequently able to add 1mph with less total timing.

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Use a quality air pressure gauge and start about 27 psi and work down untill you feel it getting alittle squirrelly on the top end. Then come back up a pound or two. Work on your launch rpm to limit spin. A little spin will keep you from breaking anything. Have fun the car looks and sounds great
 
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Watched the vid, no front end lift at all. If you fix that the car will be a lot faster, The T bars are to stiff and the shocks are wrong for drag racing, I ran 6cyl bars and 90-10's on the street with a 4 speed and radial t/a's
I could grab 2nd gear at 6500 and leave rubber for about 3ft that is how good the traction was, 11.84 @ 114.9 was the best run and that was with slicks, Oh yea I have never broke any parts ether.
 
Lots of calculators, been doing my own calculating on my ride, lopping time off the 60' and how it affects the rest has been educational for sure, for 1/4 mile mph and theoretical et this one says:1/4 Mile ET from MPH. If you can swing the cost, a set of Mickey Thompson ET Streets are well worth it.
 
Most of the 275 DR cars that run about where you are likes in the 20-23 range for air pressure. I'd try the high side of the range to start and pay attention to it swaying at the top end. Can get kinda squirrelly sometimes when too low.

105 mph with a good 60' should go 12.50's. 107's gets you to the 12.3 range 110 is 12.0 range

Chassis and converter are the biggest pieces to getting solid 60's
 
brian6pac said:
Watched the vid, no front end lift at all. If you fix that the car will be a lot faster, The T bars are to stiff and the shocks are wrong for drag racing, I ran 6cyl bars and 90-10's on the street with a 4 speed and radial t/a's
I could grab 2nd gear at 6500 and leave rubber for about 3ft that is how good the traction was, 11.84 @ 114.9 was the best run and that was with slicks, Oh yea I have never broke any parts ether.
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I saw a little front end lift, getting a better pair of tires on the rear would definitely change that too ! what I saw, I wouldn`t go back till I changed them !
 
brian6pac said:
Watched the vid, no front end lift at all. If you fix that the car will be a lot faster, The T bars are to stiff and the shocks are wrong for drag racing, I ran 6cyl bars and 90-10's on the street with a 4 speed and radial t/a's
I could grab 2nd gear at 6500 and leave rubber for about 3ft that is how good the traction was, 11.84 @ 114.9 was the best run and that was with slicks, Oh yea I have never broke any parts ether.
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Thanks for the input. I understand lighter torsion bars would soften the front end and allow it to lift a bit more., allowing for more bite. I'm not willing to go that far though, since this is a street car and although obviously not optimized for 1/4 drag racing, I think the .890 bars in it now are a decent compromise. Hopefully I can cut a few tenths off with what I've got.

crackedback said:
Most of the 275 DR cars that run about where you are likes in the 20-23 range for air pressure. I'd try the high side of the range to start and pay attention to it swaying at the top end. Can get kinda squirrelly sometimes when too low.

105 mph with a good 60' should go 12.50's. 107's gets you to the 12.3 range 110 is 12.0 range

Chassis and converter are the biggest pieces to getting solid 60's
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Thanks Rob. When the current tires are worn, I'll definitely go with a set of DR's. In the meantime, I'll play with air pressure and play with RPM a bit. The car has new HD leaf springs, so I'm not sure how much an adjustable pinion snubber would help. I suppose I can make one and see if that helps as well. I'll keep you all posted.

Any idea what a decent MPH would be for my combo? I'd be happy with a 108, but I don't really have a good frame of reference.

famous bob said:
I saw a little front end lift, getting a better pair of tires on the rear would definitely change that too ! what I saw, I wouldn`t go back till I changed them !
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Thanks. That's definitely on the list.
 
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mopowers said:
Thanks for the input. I understand lighter torsion bars would soften the front end and allow it to lift a bit more., allowing for more bite. I'm not willing to go that far though, since this is a street car and although obviously not optimized for 1/4 drag racing, I think the .890 bars in it now are a decent compromise. Hopefully I can cut a few tenths off with what I've got.



Thanks Rob. When the current tires are worn, I'll definitely go with a set of DR's. In the meantime, I'll play with air pressure, install a pinion snubber, and play with RPM a bit. I'll keep you all posted.

Any idea what a decent MPH would be for my combo? I'd be happy with a 108, but I don't really have a good frame of reference.



Thanks. That's definitely on the list.
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What is your combo? gear, trans, etc.
 
mopowers said:
9.6:1 340, rhs heads, 231/561 HFT cam, RPM airgap, 750dp, 1-5/8 headers, 9.5" converter, 727, 3.91, 275/60s.
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Put some 235/60/15 26" tire on for the track, 20 psi. That will get you approx 6K at the stripe and 110 mph. I run the same combo except home ported j head, low gear set 904, 235/60/15 MT ET street drag radial, 1-2 shift 6K, 2-3 shift 6200. I'm putting IMM LAX heads on this week and will let you know what I run when the change is dialed in. I dri ve 50 miles to the track and chassis setup was the key for better ET.
 
mderoy340 said:
Put some 235/60/15 26" tire on for the track, 20 psi. That will get you approx 6K at the stripe and 110 mph. I run the same combo except home ported j head, low gear set 904, 235/60/15 MT ET street drag radial, 1-2 shift 6K, 2-3 shift 6200. I'm putting IMM LAX heads on this week and will let you know what I run when the change is dialed in. I dri ve 50 miles to the track and chassis setup was the key for better ET.
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What's your rpm at the stripe? I was running 235/60's and turning 6k w 3.73 gears
 
Unless you must run a DR why don't you bolt on a pair of 8.5x26" bias slicks, then its only messing with shocks perhaps and that snubber you mentioned to cure your 60ft issues, you can lean on the verter then and use all of what you have....you should then see those mid 12's. I also think your carb is on the small side with that head/cam combo.
 
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