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Pinching/Tubbing/9"rearend


Guest Anonymous

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Guest Anonymous

Alright Gentlemen, the time is come when I must begin this work and I want as many pics and as much advice I can get from you all! This includes the sheet metal work.

 

I want to prepare a 9" ford rearend with 4 bar and it's crossmember, rear frame rails, and full frame rails from the 4 bar cross member all the way up to the fromt including all those necessary crossmembers.

 

The engine will be a normally aspirated "Full Houe" BBC with TH400 trans.

the 9" rear with 1" axles, big bearings etc. The tires are MT29X18.50 wrinkle walls mounted on 15" x 14" wide rims.

 

The car is a rust free 1970 240Z. It is presently fully stripped and on jack stands. The structual strength of the work preformed must be able to withstand at least 600 HP at the rear wheels.

 

I have a smaller sheet metal saw ($75.00), acetylene torches and a MIG welder (which is on the way). I fear I am not yet equipped to do the work and need a "Sawsall" for the sheet metal cutouts. Please advise etc.

 

This is not a rush job. I expect the whole thing to take about 2-1/2 years, but getting started is very important to me so I can keep planning on ahead. You can E-maol me to your hearts delight. If the data is too large then split it up and send it that way. If it is still too large then I will pay for delivery of your CD's containing your personal experience pic's and advice.

 

Shall we begin?.....

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Build a complete subframe that puts the 4 link in the correct geometry. Then work on attaching that subframe to the 240Z chassis. Don't try to adapt the 4 link to fit the 240Z chassis or you'll end up with a car that won't hook up.

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An improper rear suspension design for drag racing won't let all the weight transfer or won't let the weight transfer in a smooth, predictable fashion.

 

Just look at what Ford did with the Fox chassis Mustang. They made a number of compromises in their 4 link design because of chassis re-use (cost) and the rear roll centers do very strange things just before the inner links bind. Most folks who drag that chassis switch to a torque arm or a three link design.

 

Most of the reasons for that switch are to get predictable, consistent launches. Its tough to cut a good light when you're not sure what the rear suspension is going to do, run to run.

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Guest Anonymous

John;

 

I am not ever going to run the strip but maby once to get an official time. But are you indicating that I should consider ladder bars instead? You'll have to excuse me because of lack of actual experience in this matter.

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My mistake. I assumed that making such a severe change to the rear suspension was for a dedicated drag car.

 

Ladder bars, slapper bars, overriders, etc. are all traction band-aids to a rear suspension that's not optimized for launching. Since your car is going to be, primarily, a street car (there I go assuming again) you're going to have to make compromises.

 

With that assumption, I personally feel that the Z IRS with an R200 rear is a better choice for a compromise street rear driveline/suspension. For the 99.5% of the time when you're not doing a full throttle launch on the street, the R200 will work great with 600hp.

 

If you're still concerned I would recommend remainming with an IRS and look what Scottie has done with a Corvette rear driveline and suspension. You'll be much better off going that route then turning the rear of your Z into an early 1960's pickup truck... :wink:

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  • 11 months later...

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