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With regards to my post last week about hesitation with an Edelbrock 2121 and 1406 carb on my 289, I contacted Edelbrock and they recommended changing the step up springs and metering rods to a silver(8in Hg.) spring and a .073X.042(#1455) rod.

I did this today and re-adjusted the idle mixture and took it out for a spin. When cold, there is still some hesitation but is is virtually gone once warm. However I noticed a significant increase in response which means it was probably running lean to begin with.

Now, I have not had the car to a track yet but from the way it runs I would guess it would be around 14 sec. in the 1/4 if I could get traction. I have been considering changing the rear end from the non-posi 2.79 to a posi 3.25. I have a C4.

Well while out for my test drive I stopped on a lonely country road and without holding the brake I nailed the throttle. The tires are 195/75/14 and I immediately had rubber squeal. Then it stopped and I thought the trani was slipping but the tires had began to spin and smoke. I kept the power on and wound up leaving over 200 feet of rubber and smoking up the whole street. About 1/2 or so of the rubber was twin tracks. I was amazed that I could do this just by nailing the throttle with 2.79 gears. How did I get twin strips without having a posi?

Obviously this would limit my acceleration in a race. If I up the rear end ratio to 3.25 even with a posi this would make the tire spin problem worse. So now I am re-considering. What do you think I should do? Would fatter tires help?

Thanks

Steve D
 

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I'm not a drag racer, so I can't help you with the mechanical stuff but I can tell you that the key to fast starts with a street car is to get the car in motion then build speed. Forget the smoke, just get the car rolling before you punch it and then shift as close to the peak of the power curve as possible.

As for tires, the bigger the contact patch the more traction you'll have. You can't do better than slicks, which are all contact patch. If you need tires that can do double duty, look for a tread pattern that optimizes the contact patch while retaining the ability to channel water.

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Thanks for the update on the Edlebrock. I have the 1406 on my '66 and the 1405 on my '69. I had switched the carbs, and the '69 also had a bad hesitation using the 1406, so I swapped back ... I think mine was the same problem ... running lean (1405 is jetted a litte bigger out of the box).

I'm curious to hear other responses about your "2 track" mark with an open rear. I, too, have an open rear in my '66 and can also lay down two marks. Also, like you, I didn't think this was possible with an open rear, so I'm as confused as you *LOL*.

Fatter tires will help your traction problem, but won't make it go away /forums/images/icons/smile.gif. I have a serious traction problem as well with my 3.00 open rear running 225/60x15's in back.

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The reason a open rear spins the right tire most of the time is because of the
torque put on the rearend by the drive shaft. If you put on the emergency brake
of a open rear end and give it the gas, both tires will spin because they both have
resistance. When you gas it in the dirt with a open rear end some times both tires will
spin. On the street if you hit it hard, both tires will spin for a while, then one will take
over. When torque is applied to a open rear end, both tires drive the car until there is
more torque than one of the tires can handle. In your case niether tire could handle the
torque. 3.25 gears will help because the tires spin slower at a given rpm than they do
with a 2.73.
 

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Lower gears will spin less out of the hole. You need some 8 inch wide tires or 9's if they will fit. Once it starts to try and hook you'll probably also get spring wrap up so some slapper bars or overrides/underrides will help that. If you keep burning down the tires with your open track you'll wind up breaking a spider gear in the rear end. They are especially prone to that if you start spinning on grass or dirt and then get up on the asphalt. If you still have a little hesitation on initial launch try going a notch closer to the carb on your pump shot lever. More initial timing can also help a launch stumble.




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Hello,

I was just reading your response about "lower gears spinning less out of the hole". My car has a big upper RPM cam and I have little rubber off the line so I am planning on going to a set of 3.25 gears. I simply assumed that they would burn more rubber and that I may have to invest even further in a posi.

Can I move from an open 2.79 to a 3.25 and keep my open rear? Should I expect even less rubber?

Thanks, Greg.
 
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