Estimated 1/4 mile - 71 Roadrunner 340 4 speed

[340runner]

Okay, sorry if this topic has been posted before, but with the new season coming up for me and is my first true season racing, I'd like to know what I'm getting into performance wise and ET times.

I have a 71 roadrunner with a 340 that's lightly modded but by the previous owner, so I'm unsure of what pistons so I don't know compression ratio but it's .030 over, speedmaster heads, a Comp Cams 243/257 thumpr, and a holley double pumper 750cfm and a eddy Torker 2 340.
The trans is a rebuilt 23 spline close ratio trans, 1 to 1 final drive on a Mcleod steel flywheel and street extreme clutch.
Rear end and suspension is a 8 3/4 with 3.55s and a detroit truetrac, with freshened leaf springs and KYB shocks, on 295/50/15 cooper cobras.

So to get to the point, so far on a dragy I'm pulling 2.5 60ft times spinning through 60ft and my best 1/4 is 14.76 seconds at 96.53mph. Is this what I can basically expect at a strip, and would you guys have any insight as to how much slicks would improve my ET and would it be worth it?

Also, if I were to get tires, what would you all recommend, again sorry for the long winded post but I have very little experience regarding this field

Edit* forgot to add not sure if it was assumed but I also have Doug's long tube headers

Thanks

 

[69sunfireGTX]

14.7 is what you should get from a slightly better than stock 340 with 3.55 gears
The stick will probably slow you down a bit

 

[kiwigtx]

Someone else built the car? My guess is slicks will help you break a 14.2 second quarter.

 

[RemCharger]

Should be able to get into the 13s..... if everything is optimal

 

[340runner]

14.7 is what you should get from a slightly better than stock 340 with 3.55 gears
The stick will probably slow you down a bit

Yeah, especially since my shifting is not the greatest from 2nd to third, I still need to adjust it from my previous post on my history.

 

[340runner]

Someone else built the car? My guess is slicks will help you break a 14.2 second quarter.

I got it last march, actually my first car at all, and it came from the factory with a 4 speed and he had the original one, but it had a 727 at that time. Since I got it, I swapped back the 4 speed as he had all the parts, but he had the motor done. Just right now trying to get everything in line to get the best times I can for my local dragstrips high school drag so looking for advice from people more experienced than me

 

[RemCharger]

A bit of tire spin in a; 340, in a bbody, with a 4spd can't hurt longevity. May even help ets

 

[340runner]

A bit of tire spin in a; 340, in a bbody, with a 4spd can't hurt longevity. May even help ets

I mean it's a lot of tire spin though, I spin and hear tires screeching through 60ft, and if I really let off it bogs down

 

[RemCharger]

A lot of variables , suspension etc, have to see how it reacts to the hopefully prepped track surface

 

[RR Fan Dan]

Drag radials will help. MT et streets you can’t go wrong, they are street legal too. That is until you do a few smokey burn outs. . Its all about getting your 60 foot times down. 1.5-1.6 is what you are hoping for. Hard to get better than that consistently. You need traction. At the track you can get the tires hot in the water box which will help you hook up better. A line lock would help for consistency of burn outs. You can also shave off time by working on your reaction times. The 727 with a 3000 or so stall converter would also give you better times. With 96.6 trap speed you should be in the low 14’s /14.10 ish roughly with perfect RT and a 1.55 60 foot. To get into the high 13’s / 13.7 your trap speed will need to be 100 mph. You could lower gears to get that. 3:90

 

[340runner]

Drag radials will help. MT et streets you can’t go wrong, they are street legal too. That is until you do a few smokey burn outs. . Its all about getting your 60 foot times down. 1.5-1.6 is what you are hoping for. Hard to get better than that consistently. You need traction. At the track you can get the tires hot in the water box which will help you hook up better. A line lock would help for consistency of burn outs. You can also shave off time by working on your reaction times. The 727 with a 3000 or so stall converter would also give you better times. With 96.6 trap speed you should be in the low 14’s /14.10 ish roughly with perfect RT and a 1.55 60 foot. To get into the high 13’s / 13.7 your trap speed will need to be 100 mph. You could lower gears to get that. 3:90

Well, I blew up the 727 so that won't work, I also did have a 3000 stall but the standard is a lot more punchy in my experience, and it being also a street car is more fun to drive. Would you still recommend drag radials with a 4 speed, and are the ET street s/s decent for that? I just yesterday actually saw the pair in the size I'd at my local speed shop picking up another pair of motor mounts, before I put the car in the garage for winter I broke my set of poly ones, which makes 2 sets of rubber and 1 poly set i went through in 6 months.
Now I'm going with solids and hoping they don't shake me to death.

 

[RemCharger]

Its all about getting your 60 foot times down. 1.5-1.6 is what you are hoping for. Hard to get better than that consistently.

14.10 ish roughly with perfect RT and a 1.55 60 foot.

Lol maybe a 2.0-1.9..
1.50s is in the 10s

 

[340runner]

View attachment 1789434

Lol maybe a 2.0-1.9..
1.50s is in the 10s

I mean hey, I wish the car was capable of running 10s, maybe after I actually install subframe connectors, torque boxes, a nice 340-416 stroker, and some thick slicks before my 8 3/4 goes kaboom. We all have dreams though

 

[RR Fan Dan]

Would you still recommend drag radials

They won’t hurt, but if its a street car and you are only going to the track to play around, then keep good street tires on it, and you can always get another set of rims with slicks just for the track, and change wheels at the track

 

[340runner]

They won’t hurt, but if its a street car and you are only going to the track to play around, then keep good street tires on it, and you can always get another set of rims with slicks just for the track, and change wheels at the track

Well, I'm not sure if cooper cobras are good, they're hard as a rock, made a lot of smoke and still practically new tread while being horrendous in the rain, i remember driving to work and almost got perpendicular with the road without even stepping on it. I'm either in between bias ply slicks on a second set of wheels since I heard drag radials don't play with stick shifts well, or just run the et streets. I finally had to get a daily for over the winter so I don't drive the car in rain or any inclement weather by choice. Dailying the roadrunner with AC deleted and the heater core removed was hell

Second note, not sure if Byron Dragway would classify the ET street s/s as DOT street tires, need to run them in my planned class so that would also influence my decision

 

[340runner]

Also for more reference, not sure if it would help at all here's my fastest so far 1/8th and 1/4

 

[RR Fan Dan]

Those are respectable times for your set up and car. 14’s back in the day was the ****. As far as tires go, you definitely don’t want to drive around with ET streets in the rain.

 

[RemCharger]

Also for more reference, not sure if it would help at all here's my fastest so far 1/8th and 1/4View attachment 1789452View attachment 1789453

To compare, here's a well sorted bracket car. Note the 1/8 mph. Similar.
This was a challenger with a bum 440, but very consistent

 

[R413]

If you get tires that won't spin then it will bog with a heavy car, small block 3.55's and a 4 speed.

And forget about a 1.6 sixty foot with that combination.

4 speeds are fun to drive but tricky to get good times.

 

[496 polara]

Check the basics first. Timing been checked? Spark plugs read? Lean or rich? What rpm are you shifting at?

Call me crazy but that setup with 3.55 gears would likely perform better with a performer rpm intake.

For a dual purpose drag radials the Nitto 555 drag radials always worked well for me on a heavy B body that ran 12.0's and didn't give issues in normal street driving.