Hoes NHRA allow a solenoid shutoff switch like those by Painless Perf or do they need to be completely mechanically operated?

They are allowed

WOAH! STOP. I was in actual contact with NHRA over this issue a couple years ago and the answer was flat out NO!

So unless you have contacted NHRA resently I would advise doing so before you buy and install this.

The reason that was given was is if the control wire going from the on/off button was pinched (grounded) in a collision the battery disconnect would turn back on!

I have just finish dealing with this cut-off situation with NHRA/IHRA and wiring it to work with an alternator. The switch has to be a manual switch, which can be cut-off out side of the car and clearly marked. Certain et's have to have a push/pull, with off being pushed inward. The handle has to extend out beyond the bumper/back of the car.

Check into it carefully, before your buy and install.

Wow!!Interesting..I actually know some prominent chassis builders that have been doing this for several years now on NHRA super comp and super gas cars.

I just spoke wit Jonathan Adams, NHRA Div 7 Director. He siad that this type of switch is legal and fully in compliance with the intent of the rule as long as it cuts off ALL elect supply to ALL parts of the vehicle ()Motor, pump, fan, etc...)
Has anyone heard anything different from an NHRA rep?