What are the proper name for them? Hood holders, clamps, fastners...I don't know. Anyway, a couple of mine seem to pop off when I drive the car. Can they be tightened up? They do turn and I wonder if turning them tightens them? Anyone have a tip on this? Thanks in advance...

Zoolou, the latches don't tighten by turning them, most likely they have weak or broken springs.

Are they repairable?

I have not tried to repair one. There are several variations 1929 thru 1931, some black and some chromed, and for different assembly plant locations. There could be some repros out there somewhere. Have you contacted the Filling Station?

The filling station has hood doors and hood door springs to replace the old ones you have. Call 1-841-6622 If you need help on what you need.

The 30-32 (32 Commerial) candy cane style hood latches are repairable. The top (hook part) screws onto the shaft. It is best to clamp the tube in a vise with wood or other soft material between the tube and jaws. Be careful not to put too much pressure on the tube as it can be distorted. It is rolled and has a seam that can be collapsed. You may need to heat the top a bit to unscrew it. You will then need to take a grinder or file to remove the crimped end on the shaft. Or if careful you can straighted the crimp even with the shaft. Be careful if the spring is still ok as there will be some pressure that will be released. Once the shaft is free then the rest of the assembly can be taken apart. Fix what needs fixing and then put it back together. If you want to use the original shaft then you will need to wedge the top washer down the tube to weld the end to retain the washer. It is not too difficult. All you need is to put a small dab on the top of the shaft. If you don't what to use the original shaft you can make one from a long bolt. Then you can use a nut and loctite to secure the nut. If you have problems email me.
Be sure to have the top and tube rechromed before reassembly.
Or you can buy reproductions (that are easy to detect) from the Filling Station or other repro suppliers.

The 1930 "Candy Cane" latches for the passenger cars were cad. plated, and the 1931 passenger car "Candy Cane" latches were chrome.