Thread: NHRA required frame thickness

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I've been trying to find out what gage the frame has to be for NHRA rules. Does any one know the gage or where I can find it.
Thanks for any and all help with this question.


~ Vegas ~

From what I could find in the rule book stock type frames are 2x3
x .083 wall minimum.I built mine out of 2x3 x .125 wall and had no tech issues,so you should be fine with that.
Pappy

Pappy's right.

Mild steel SFI specs. ......
For round tubing larger than 1 1/2” diameter, the nominal wall thickness is .118”
For round tubing 1 1/2" or smaller diameter, the nominal wall thickness is .108”
Exception: for round tubing used for helmet guards (#49 and #50) and cage gussets (#34, #35, and #36), the nominal wall thickness is .083”
For rectangular tubing 2” x 3”, the nominal wall thickness is .083”
For rectangular tubing 2” x 2”, the nominal wall thickness is .065”
Plate thickness and bolt diameters are minimum requirements, unless otherwise specified

Papadaddio and Pro70z28; Thanks for the info on the gage steel to use for my frame. The stock frame in the car now is 2x3 so I'll go with that size again, in the.083" gage. Ok how do I messure
for the coil springs length when there gonna compress when I sit the car down on them? The car weights about 2800pds, but most
of the weight is in the front. This is for a 65 Ranchero, no real weight in the back or not alot. Thanks



~ Vegas ~

Are you using the stock coil springs on the front, or coil over shocks?? I usually just remove the coil springs and shocks when I am building a car with stock type suspension and use a peice of threaded rod bolted in place of the shocks to simulate where the car will be at ride height. If I am building the suspension with coil over shocks, then I use a peice of tubing with holes the correct distance apart to simulate the height of the coilovers when the car is at ride height.

This is what I use in place of the rear coilovers.

Dave; The front end will be removed to get rid of the shock towers. It will be replaced with a mustang II front end.
This way I will free up a bunch of room for the engine
headers to go over the frame then back. For cleveland
heads to breath right the header must come out a couple
of inches before turning.

Right my main concerns are getting the messurments right for the rear end. Also the angle's to make sure every thing moves the way it's supposed too. I just talked to a guy that had just did a four link and had set it up wrong. He said that the rear end did'nt pivit right. From what I've heard the bottom link should be parallel
with the frame and the top link should be about 4 degress down toward the front of the car. The Yoke on the rear end will be 3deg. down. My main concern is to get the spring hight right sose when I set the car down on the new coil spring it is setting at the right height or the frame is parallel with the ground.
I mean when you set the car down on the spings there gonna compress some right, { How Much ? } This is what I need to know. I want to get the right spring. Thanks

~ Vegas ~

I built adjustable mounts so I can raise or lower the shocks. There's also some adjustment in the coilovers.

Here's a little better angle. I have the shocks mounted too low here so I can get the ride height without compressing the springs.

Very nice Pro70z28 thanks for that great tip.

~ Vegas ~