Rear suspension suggestions needed

[Splangj]

you’ll need to shorten then weld up the Mopar pinion snubber. I believe I was told to shoot for around 3/4” clearance to floor bottom. For some reason its way to tall for standard height rear ends. I’ve had good luck with MT drag radials. Best of 11.49 at 117 with 32lbs in them. And they handle very well, as long as it’s dry.

 

[padam]

Let's say the 489 makes 530ftlbs. Let's also say it makes 530ftlbs from 3000-5000rpm.
530ftlbs@5000rpm=505hp
530ftlbs@3000rpm=302hp

If you want an engine to make HP during launch, it needs to spin some rpm. With radials the tires also need to dead hook. With hooked radials, a car needs some time to gain ground speed before clutch lock-up, otherwise the engine gets pulled down where it doesn't make much power.

Say you want to keep engine rpm above 3000 with radials during launch?
...With 3.23 gears and 28" radials, the clutch is going to need to slip to about 28mph.
...If you want the engine to stay above 4000, the clutch is going to have to slip to around 36mph.
Swapping to a more appropriate rear gear would reduce the need for clutch slip time.

You might think that if the engine makes the same torque at 3000rpm as it does at 5000rpm, 60's would be the same. That's not the case, as an engine's rotating assy absorbs torque as it gains rpm. The less rpm an engine has to gain on it's way to the 60', the less torque it's rotating assy will absorb. Less torque absorbed by the rotating assy means more power will be available to accelerate the car.

If you want to play with how long the clutch slips vs how far the clutch pulls the engine down during launch, you do that by adjusting clutch clamp pressure. Dialing in launch clamp pressure helps cure spin/bog problems, also reduces the tendency to wheelhop.

A clutch hit control device such as my ClutchTamer makes adjusting clutch clamp pressure during launch much easier, without compromising the clutch's overall ability to hold torque. I often hear the 'tamer also makes bracket racing with a stick fun again

Grant

Grant maybe someday I will try your Clutch Tamer if I get back into racing.
Gus

Clutch tamer helps, but it doesn’t seem like an ideal solution to me.

For one thing it does affect your reaction time. Anyone that bracket races knows that rt is about 80% of the race. So if you make an adjustment, to manage traction or the other stuff Grant talks about, your rt’s go out the window.

I’ve been using it for the past two seasons, and still don’t have a good handle on the adjustments. The last race I attended was on a pretty good track. My first pass the clutch was slipping too much. Made some adjustments and was fighting traction problems after that.

This has been with two different clutch setups so that is part of the challenge.

Also, the device has a tendency to unwind or change adjustment on its own due to vibration.

Grant, I’m not trying to bash you here, just sharing my real world experience.

 

[weedburner]

Clutch tamer helps, but it doesn’t seem like an ideal solution to me.

For one thing it does affect your reaction time. Anyone that bracket races knows that rt is about 80% of the race. So if you make an adjustment, to manage traction or the other stuff Grant talks about, your rt’s go out the window.

I’ve been using it for the past two seasons, and still don’t have a good handle on the adjustments. The last race I attended was on a pretty good track. My first pass the clutch was slipping too much. Made some adjustments and was fighting traction problems after that.

This has been with two different clutch setups so that is part of the challenge.

Also, the device has a tendency to unwind or change adjustment on its own due to vibration.

Grant, I’m not trying to bash you here, just sharing my real world experience.

Hi padam, thanks for the feedback!

There should be a groove milled in the 'tamer's threaded rod, also detent balls installed in it's inner dial as well as outer slide bushing. I added those back in 2016, they are supposed to keep the adjustments from casually rotating due to vibration. Can you feel the detents engaging when you rotate the adjustments?

It's probably best for a bracket racer to tune the 'tamer to dead hook on the worst surface that they are likely to run on. If the car dead hooks on a bad surface, you won't need to change anything if the surface improves.

The first version of the 'tamer came about just as an effort to keep from breaking transmissions. It turned out to be a very effective way to keep the transmission alive, but the softer clutch hit caused a huge engine bog problem. Eventually I made an adjustment where the clutch seemed to slip waay more than I thought it should, but on that pass the car picked up almost half a second. From there I found that what I previously thought was too much clutch slip didn't actually damage that clutch at all. A combination with a previous best of 6.51 eventually went 5.73 on the same clutch with only 'tamer adjustments. That was back in 2011. Same pressure plate is still in service today, except currently with a less aggressive dual friction disc.

Clutches are much like brakes. As long as the components don't reach a temp that causes permanent damage, they will last a good long time. Keep in mind they need to cool between hits for consistency, avoid hot lapping if you can.

Grant