I have a 66 coupe with a 4 speed 3:50 posi gear with 215/60 14 inch radial tires. What result do I get by going to a taller and a bit wider tire. Do I gain top end speed but slower on 60 foot time? I am confused about this. This car is used for mainly street and a occasional strip use.
going to a bigger (wider) tire will help you get grip out of the hole, so that should make your 60' times faster. This usually helps you pull a better 1/4 mile time. As for a rim/tire height combo, that can affect what RPM you cross the line at, and should also affect your MPH and 1/4 times as well. Ill let the other guys who know far more then me about drag racing answer that.
I have a 66 coupe with a 4 speed 3:50 posi gear with 215/60 14 inch radial tires. What result do I get by going to a taller and a bit wider tire. Do I gain top end speed but slower on 60 foot time? I am confused about this. This car is used for mainly street and a occasional strip use.
Nick's right in that you'll have,in effect, a lower, numerically, gear. But more tire width isn't always great unless you're making a ton of HP/TQ, at least if you're talking about a slick or some DOT approved slick. The nice thing about the flexible sidewalls is that you have more tire in contact with the ground for a longer period of time.
That being said, I know of guys that went with a wider tire that was the same height and spun worse. I believe it had to do with lbs/sq inch. Now if you changed your rear gear in addition to putting on a taller tire, so that your gear ratio would effectively be the same, ie. your speedo still reads the same, you should gain some on the top end without affecting your 60' time so much. If you lower your tire pressure a bit at the track, that can help with tire spin as well.
With what you're using your car for, I wouldn't worry about 60 foots or top speed so much than kicking the bowtie in the next lane's butt.
a 215/60-14 is a pretty small tire in fact it's quite a bit shorter than even a stock sized bias ply tire so in effect you actually have a lower rear gear ratio than what would be considered normal for the car. for example, if you were using a stock size tire your equivalent rear gear ratio would be actually be closer to like a 3.70 gear. remember we're talking hypothetical here.
if you were to go to say a 245/60-14 you'd be closer to that that theoretical stock size tire 3.55 gear ratio. so increasing the rear tire size is going to raise your MPH at the end of the track as well as lower your RPM through the traps. if the taller/wider tire helps the car hook better your 60' time should be lower as well.