C3 Drag racing rear IRS

So what is the trick method to prepping the stock IRS to launch properly at the drags? Solid axle, not an option. I know people have done it. I need details.:drink:

1st question, what power levels? Are you referring to beefing up the IRS or are you talking about getting it to hook with respect to wheel hop, camber curve and so on?

Twin_Turbo said:

1st question, what power levels? Are you referring to beefing up the IRS or are you talking about getting it to hook with respect to wheel hop, camber curve and so on?

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I will have Ben answer the questions. It's his 82 LS conversion.

Jeff I wouldn't even consider a 82 diff for this application. If you're running good power and hookup you'll break that diff. A tune 10 bolt may last a while all depends on power and # of passes. The best IRS would be the 12 bolt in an iron unit. Add to that the 31 spline axles, 3.5 steel shafts, Tom's spring and a whole lot of cash.

But Monty never broke his, and that guy Motorhead on CF, I'm pretty sure he still has his Dana one also. Something must be keeping them together!

I'm at 390 to the wheels. My best is a 12.6@113 with a 2.0 60'. I run MT ET DRs (Street legal drag radials). There is a very fine line between bogging and spinning where it kind of hooks. But I absolutely cannot launch hard, they'll just spin, yes, the heated DRs will spin. My Aluminum Dana 44 has held up to dozens of launches and seems fine.

In front I have 550lb springs and Bilstein Heavy Duty Shocks. In back I have a the VB&P Dual Spring set to 420 and Bilstein Heavy Duty Shocks. Camber rods replaced with Heim Jointed rods. I have spherical joints in the HS setup at Dick Guldstrands. It sticks and handles great, just can't launch hard. My only obvious guess is that I'm just not getting enough weight transfer to make the tires grab hard.

Good luck is all I can say. Many broke on the street with stock engines. Mike likes them, have him install a steel cap, but I still wouldn't bring it to the track.

Twin_Turbo said:

But Monty never broke his, and that guy Motorhead on CF, I'm pretty sure he still has his Dana one also. Something must be keeping them together!

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I'm wondering if a removable spacer could be installed at the track to act like a traction bar. I.E., some kind on metal bumper to limit travel. (That make sense?)

Hi Jeff,
The Dana 44 uses some parts comparable to the iron diff in strength. I can install a steel cap which fixes the weakest link. The other problem will be the size of the rear pinion bearing. It needs to be larger for abusive driving.
It really depends on how much power you're putting to it. 400 hp with an auto and street tires should hold up fine. 500 hp with a stick and slicks will probably snap the case in half. It may handle it but I doubt it.
Here's your choice:

stock dana 44


Dana 44 with steel cap


stock iron diff


Iron diff with steel caps and Toms 1350 axles


12 bolt with 1480 axles


and if money doesn't matter, Dana 60


As for traction a stiffer spring and stiff shocks. Anything to keep the back end from squatting. The more it squats the less downward force is applied to the tires. The body isn't really squatting. The trailing arms are being forced up into the body do to trailing arm angle.
Mike

tracdogg2 said:

Hi Jeff,
The Dana 44 uses some parts comparable to the iron diff in strength. I can install a steel cap which fixes the weakest link. The other problem will be the size of the rear pinion bearing. It needs to be larger for abusive driving.
It really depends on how much power you're putting to it. 400 hp with an auto and street tires should hold up fine. 500 hp with a stick and slicks will probably snap the case in half. It may handle it but I doubt it.
Here's your choice:

stock dana 44


Dana 44 with steel cap


stock iron diff


Iron diff with steel caps and Toms 1350 axles


12 bolt with 1480 axles


and if money doesn't matter, Dana 60


As for traction a stiffer spring and stiff shocks. Anything to keep the back end from squatting. The more it squats the less downward force is applied to the tires. The body isn't really squatting. The trailing arms are being forced up into the body do to trailing arm angle.
Mike

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Thank you for your input Mike. He/we know it's gonna grenade someday, and the choice of diffys will be made at that time.
The car already has super stiff springs and shocks, but still will not launce correctly. I am thinking of what would have the same effect as a traction bar, IE, limiting the T/A travel.

Big Bird when you look at the rear suspension to limit how far it goes is right in front of you lol. The factory bump stop that hits the trailing arm to limit the uprward movement. What you can do is simple. Just take a 1" by 2" piece of square tube and put that between the bumper and the frame. If it does not allow it to move far enough you simply trim the rubber pad down the amount needed. You might even be able to go to your local High Performance shop and pick up some rear suspension bump stops instead of cutting the factory ones. That is if he has the stiff rear spring and good shocks to go along with it.

This simple trick has been around forever. But it took Jim 427HotRod to remind me of it lol.

BRB I will even take a pic for you lol.


I have not cut on the bump stop as of yet since it has not been on the ground.

I would like to add that a person should mount everything as solid as they can. I have the locating disc's as well as a solid disc to replace the rubber snubber.

Thats how this other guy I know did it, that and he chained the front a-arm so it didn't droop too far.

The nice thing about doing it this way is both sides do not have to match lol. That way you can tailor how the car launches on the bump stops.

I hope you enjoy the Center Grill Chris

I am not sure how my car will work out as I have a rear spring right at 500 LBS that was picked for me by VBP. But it all should work out just finer than frogs hair.

If it's not enough I have another that is 580

I bet the traction bar type of deal would help some too

Is it Glass or Steel ? But to be honest I think the one I have should be enough as I do not plan to run slicks. This is just a slow street car with a tiny little itsy bitsy 468 CI Big Block 3000 Stahl TQ converter with 3.73 Gears. I feel for the street that a little less than 600HP is enough lol.

No matter what Jim says lol.

Well I am heading back out into the garage and dismantle the SB some more and everything else in the way to remove the engine and trans in a few days I hope when I get the help as this is just something I do not like to do alone. Been there done that do not wish to go back again lol. Then rebuild the Turbo 400 and clean everything up to start putting the Big Block in.

SHAKERATTLEROLL said:

Big Bird when you look at the rear suspension to limit how far it goes is right in front of you lol. The factory bump stop that hits the trailing arm to limit the uprward movement. What you can do is simple. Just take a 1" by 2" piece of square tube and put that between the bumper and the frame. If it does not allow it to move far enough you simply trim the rubber pad down the amount needed. You might even be able to go to your local High Performance shop and pick up some rear suspension bump stops instead of cutting the factory ones. That is if he has the stiff rear spring and good shocks to go along with it.

This simple trick has been around forever. But it took Jim 427HotRod to remind me of it lol.

BRB I will even take a pic for you lol.


I have not cut on the bump stop as of yet since it has not been on the ground.

I would like to add that a person should mount everything as solid as they can. I have the locating disc's as well as a solid disc to replace the rubber snubber.

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I like it. I just would like to make it removable/changable for street/track. I suppose it wouldn't take that long to change out.

I do not know why you would not just leave them on but okay lol. I would get another stock set of bump stops. And keep the ones that you have to fit and mounted on the 1" by 2" piece of square tube. And mark them as to what side they come off of. And just change them out when you wish.

After thinking about this for a bit since you wish to change them out then make the ones you will race with the correct length so as to not let the half shafts go above level or by much. You would wish to have the half shafts as level as you can so that all of the force on them is as even as you can make it to spread out the load.

SHAKERATTLEROLL said:

Big Bird when you look at the rear suspension to limit how far it goes is right in front of you lol. The factory bump stop that hits the trailing arm to limit the uprward movement. What you can do is simple. Just take a 1" by 2" piece of square tube and put that between the bumper and the frame. If it does not allow it to move far enough you simply trim the rubber pad down the amount needed. You might even be able to go to your local High Performance shop and pick up some rear suspension bump stops instead of cutting the factory ones. That is if he has the stiff rear spring and good shocks to go along with it.

This simple trick has been around forever. But it took Jim 427HotRod to remind me of it lol.

BRB I will even take a pic for you lol.


I have not cut on the bump stop as of yet since it has not been on the ground.

I would like to add that a person should mount everything as solid as they can. I have the locating disc's as well as a solid disc to replace the rubber snubber.

Click to expand...

I can kind of understand lowering the bump stop so that it "locks" the wheel travel in place, in other words lowering it so that it's in contact when at rest. But do you mean simply lowering the bump stop to "limit" the amount of travel . . . doesn't that mean it'd slam into the stop on launch?

BTW, I have a VB&P Dual Mount set to 420 and Bilstein Heavy Duty shocks. It really doesn't squat much at all. I just can't nail it, even on DRs, 2,500 is about the highest I can launch at. I do have a solid pinion mount, but haven't installed it yet. I have solid bushings for the TRs. The diff is an aluminum D44, regeared to 3.73.

Other things that have been suggested to me are
-Remove front anti-sway bar
-Get adjustable shocks for the front so they can be made softer for rising


At a world famous crappy track I'm at 12.6@113 with a moderate launch (2.0 60'). If I can get that down to a high 11 with a little more power (I have some easy power to be gotten) and better traction setup, I'll be happy. I'm working on something else for the stupid fast. :stirpot:

It will not or should not lock the trailing arms in place. There should be some movement. And yes when you launch it will hit the bump stops.

But what do you wish to do with the car? Are you going to drag race it only or is it going to be a street car. You have to decide on what you wish the car to do.

If you are going to just drag race it with the parts you have then yes you would remove the front sway bar and put in 90/10 shocks in the front and some 50/50 rear shocks. And the list goes on from there.

But I am not a dedicated drag racer. I like my car to handle on the street and yet have some get up and go. I am would guess to say I am looking for more of an over all car. It will do everything okay but not dedicated to one thing.

You have to decide on what you wish your car to do and then build to that.

SHAKERATTLEROLL said:

It will not or should not lock the trailing arms in place. There should be some movement. And yes when you launch it will hit the bump stops.

But what do you wish to do with the car? Are you going to drag race it only or is it going to be a street car. You have to decide on what you wish the car to do.

If you are going to just drag race it with the parts you have then yes you would remove the front sway bar and put in 90/10 shocks in the front and some 50/50 rear shocks. And the list goes on from there.

But I am not a dedicated drag racer. I like my car to handle on the street and yet have some get up and go. I am would guess to say I am looking for more of an over all car. It will do everything okay but not dedicated to one thing.

You have to decide on what you wish your car to do and then build to that.

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Same position. As for shocks, do you run adjustables?