I found photos of this car online (not mine), but have several questions.

Would this cage be NHRA legal if it didn't have the two long rear braces and only had the two X'd rear braces? Or would they need to be straight back and not crossed?

Also, is there a requirement for a minimum angle that two rear braces must be at?

I've look through the rule book, but the section on rear braces for full bodied cars is a bit confusing

Stupid me! I found the answer to one of my questions:

Not sure what is going on with OP's pictured incomplete cage.

Disregard the rest of the cage in the photo - it's obviously under construction. I was asking specifically about the rear braces and that was the closest photo I could find to illustrate my question. Maybe I was unclear. Can rear braces be crossed (like the X-brace in the top photo), or do they have to be straight back? That's what I was getting at. I apologize for any the confusion.

Call or E mail NHRA tech to get the straight, accurate scoop, information

Your question is answered in the bar size part, A-two bars @1-5/8 CM any length just like the picture. If it has to have an X then the picture NEEDS changing

Concerning the rear bars in the photo...

IF they are both 1.625 x .120 and IF they are in on the correct plates, then either the straight bars going to the back OR the X brace, as long as it exceeds 30 degrees, would satisfy the "B" bars in the cert by themselves. An inspector would only be concerned with the bars needed to satisfy the cert.

ETA...per the rule book, additional "B" bars allow you to use smaller tubing and still satisfy the cert. i.e., in the photo the four rear bars could be 1.375 diameter. Or the long bars could be 1.250, IF the X is 1.625.

The "B" bars can be straight or Xd, But by Xing the short bars, rather than having them in individually and straight back, you are gaining a lot more strength and rigidity with no increase in weight or "stuff" in the car.

Welding the long bars to the body structure at the base of the rear window will tie those bars to the body at that point, using one to support the other and further stiffening the body.

Don't forget the "D" bars. Main hoop to frame tie. A second pair at that point on the main hoop being used to support the area of the floor at the front spring box will also be beneficial, especially if using leaf springs.

Thanks guys. I appreciate the input I knew I shouldn't have posted that photo I found online. It's just confusing the general question I had.

I did send an email to NHRA and heard back. Excellent suggestion btw, Cab. I had no idea NHRA answered emails. Per that email response and as mentioned, If there's only two rear bars, they may be X'd, but they said the two bars must attach to the horizontal portion of the main hoop. Does anyone know where in the rulebook that is stated? I'm failing to find it.

In my 66 Dart, have four bars currently, similar to the four in the top photo. Two long 1.25" bars to the rear of the trunk (attached to the horizontal part of the main hoop), and two 1.625" X'd tubes from the outer radii of the main hoop to the side of the inner wheel tub (>30 degrees). I was just curious if I could cut out the long 1.25" bars and still be legal. Sounds like no because the two X'd bars are tied to the radius and not the horizontal portion of the main hoop.

NHRA uses SFI specs. so you need to look at them to get it straight
Nothing like getting the run around, huh

It's on the screenshot of the rulebook page above. We've always put the bars out near or partially in the radius.. I believe rule of thumb is it needs to be within 5" of the top of the cage. Not way down in or below the radius. Bars in the photo are right there. A picky inspector might say something about that.

If your X is 1.625, the 1.25 bars going to the trunk won't matter one way or the other. Inspector will ignore those. Why cut them out? They aren't useless.

SFI spec kicks in quicker than 8.50 and/or 180MPH. Slower than that is rulebook specs.

I'm not seeing where it's explicitly stated in the rulebook, which prompted my question. It says "If A (meaning 1.626"), two bars." It doesn't say they should attach to to the horizontal portion of the main hoop, though, it's probably implied by what is shown in the rulebook picture, as cudaman1969 said above. I just wish it was more clear because the photo also shows two parallel rear bars, yet the NHRA tech said X'd is fine if they're attached to the horizontal portion of the main hoop.

For me, I'm considering removing the two long 1.25" bars because I've changed direction a tad on my build. I may just redo the rear braces all together by using bent rear braces, so I can run a rear seat.

I appreciate the input. This has been very helpful.

Awhile back I had an inspection from the NHRA guy and he had to ponder my back bars, had an X off the top hoop down to shock support bar (1-5/8 dom tube) I then had two 1-1/4 bars half way down on the X bars back to where it held the aluminum plate that the body was attached (fiberglass 70 Cuda funny car body) he was thinking they had to be 1-5/8 also. I said they didn’t have anything to do with the cage just a support for body, after much thinking he agreed. He later said if I’d put CM in there he’d have given me a 25C cert because of the way i’d put it together. Like said it’s at their digression, to an extent, of what they will pass.

Where can I read up on the engineering used to make these rules?

[/sarc]

That reminds me of a disagreement I had with a city electrical inspector about grounding when I presented the current at the time NEC code book, he said "I don't care what the NEC code book says", authored and revised many times for nearly a century by hundreds of engineers and Phd's in the field.

Typical low level government bureaucrat inspector
You do need to remember that some local government agency have their own set of rules on utility, especially if they also own and operate that utility
I've had to argue with some of those local city inspectors who thought they had authority over the telephone industry in a small town in SO CA back in the early 1980, once his boss told him they did not have the legal authority over governing the telephone wiring inside or outside the new home being constructed he shut his yap