71 Pumpkin Pie Build Unflared LZ 2.2

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Byron510
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Location: Maple Ridge, BC

Re: 71 Pumpkin Pie Build Unflared SR20

Post by Byron510 »

Agreed – you’ve seen how much the X member twists in action – both in the vertical and horizontal planes? By removing the bottom of the X member, there will be significant stress on the top half. I’d hate to induce rear steering.

I too have added a large pipe for a 3” exhaust but kept the bottom of the X member in place. Pictured here is one I did recently for a local guy, and another of one I put under the Bronze nearly 10 years ago as part of an upgrade. By using a full pipe, the bottom horizontal plane remains intact. The pipe in 3/16” wall on the most recent one. The X member under the Bronze was 1/8" wall, and this one I have found flexes more than a stock X member when removing a diff. Hence the thicker pipe used on successive X members. Bridging top and bottom would be a good plan in the vertical plane.
It takes very little flex to alter suspension geometry on this X member, given the distance to the wheel from here.

Something to consider. Let us know how it goes.

Byron
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zKars
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Re: 71 Pumpkin Pie Build Unflared SR20

Post by zKars »

I decided to do this as well to make exhaust removal easier and to reduce the number of joints. I was doing the Camber caster adjuster addition welding installation

I made not quite so big a hole, 2 1/2" pipe max, and have it a bit lower than Mike's. And for insurance, I have a large removable bar that closes the gap across the bottom that adds a tension member for bending forces.

I also added another plate across the top to thicken the overall member above the hole as well just because.

I'll keep an eye on this over the next as I add 10-20,000 km and see anything nasty happens.

Here is the best pic I have. At least it shows the size, depth and the two 3/4" bolts that hold the bar across the gap.
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cartel
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Location: Langley

Re: 71 Pumpkin Pie Build Unflared SR20

Post by cartel »

i dont forsee it being a problem but time will tell . ive seen the same mod done by Mario at TSR -
ive got it capped on both sides and i believe its as strong as it was originally . could always add a bolt in bottom like Jim has done but im not convinced thats necessary.
Mike Gibson
Datsun: 71 dime; 73 Z ; GT3 240
Other: 65 + 67 Mustang ; 03 murcie
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JordanTr
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Joined: 20 Feb 2013 22:27
Location: Kimberley, BC, Canada

Re: 71 Pumpkin Pie Build Unflared SR20

Post by JordanTr »

I think using coil overs will also lessen the stress in the inner pivot and consequently reduce stress at the critical point of the cross member.

When I did mine, I boxed in the hole with 1/4” plate on both sides and used 1/4” wall pipe with the same width as the original flange to arch the bottom. I crunched the numbers rudimentarily and I’m within a few % of the original strength.

Can’t see the pics so I don’t know what yours looks like!
'72 2 door KA project | S14 Silvia RB25DET | S14 RB26DETT (sold) | '90 Audi 90Q20V (sold)
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cartel
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Location: Langley

Re: 71 Pumpkin Pie Build Unflared SR20

Post by cartel »

since the k member was out i decided to add a brace across the bottom- welded 3/8" plate on both sides and tapped and threaded .. with a 1/4" plate for the brace..
Image

this cars going to be left in "driver mode" now so i can focus on the Flared cars im building- the SR got out of hand so building a car similar to the one i had 30 years ago except now its EFI and will have all the stuff i couldnt afford then..
Mike Gibson
Datsun: 71 dime; 73 Z ; GT3 240
Other: 65 + 67 Mustang ; 03 murcie
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eastbaysolo_73
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Re: 71 Pumpkin Pie Build Unflared LZ 2.2

Post by eastbaysolo_73 »

Get her done!!!
1970 2 door sr20det cookie cutter build
My build thread
http://www.the510realm.com/viewtopic.php?f=3&t=30772
Nor Cal Meng !
iceD
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Joined: 31 Mar 2008 20:07
Location: Richmond, B.C.

Re: 71 Pumpkin Pie Build Unflared LZ 2.2

Post by iceD »

How’s this project coming along?

ice D
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cartel
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Joined: 24 Sep 2015 23:32
Location: Langley

Re: 71 Pumpkin Pie Build Unflared LZ 2.2

Post by cartel »

sitting in the shop . exhaust done. was going to pull engine to paint the bay but didnt get to it this winter. maybe next
Mike Gibson
Datsun: 71 dime; 73 Z ; GT3 240
Other: 65 + 67 Mustang ; 03 murcie
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