The Supercar Registry - Original 69 GM Derby Caps Wanted

The Supercar Registry (https://www.yenko.net/forum/index.php)

- Parts/Memorabilia - Wanted (https://www.yenko.net/forum/forumdisplay.php?f=84)

- - Original 69 GM Derby Caps Wanted (https://www.yenko.net/forum/showthread.php?t=142752)

Say I'm at the MCACN show looking at Joe Blow's really nice restored Yenko, ZL-1, COPO
etc done by XYZ shop in Bumfxxk, ID.............how inferior are the best reproduction ralley
caps when looked at by 99 out of 100 enthusiasts ?????

Thanks for the education !!!!!!!

ps. Looking for 1st design 70-74 Z-28 trim rings !!!!!!

The only repo Rally caps I remember were chromed plastic without the Chevrolet lettering and pretty easy to spot. Maybe someone has something out now but don't know why as there were plenty from Chevrolet.

I stand corrected . Classic has repos with lettering now. They also sell GM caps at 281.00 each or just the center at 96.99 each.

Chuck, I bought a set from HBC...repo ones..beautiful chrome...i was impressed

i did notice that the overall diameter of derby cap was slightly less than the GM ones...maye 3/8 - 1/2 inch or so...so when u install HBC ones, the edge of the cap lip is right at the raised section of the rally wheel. The GM ones extend past the raised section of the wheel and allow u to get your finger behind to pull them off.

The HBC ones were very impressive - also some slight lettering difference, but at about 250 a set - they make a great driver set with great polished chrome. His trim rings are very nice as well.....

Best repro caps and rings are coming from D&R right now. The rings look spot on and have the correct oval holes for the valve stem. Not the 4 clip style as they have the serated edges but real decent. Their caps are also a much higher quality than the lightweight ones from HBC. The ones HBC carry are coming from Summit's supplier of Rally Wheels. Wheel Vintiques I think

Big thank you to Ed for hooking me up with some NOS double ribbed caps & matching bottoms today. Great member to deal with, as are many here on sYc! 3gears.gif

Thanks to you too Charley for hunting through your personal stash for me. Hope I didn't inconvenience you?

Got everything I need for now and trust these will look great on the 69 when it's finished up.

http://i1218.photobucket.com/albums/...28/Derby_1.jpg

http://i1218.photobucket.com/albums/...8/Inside_1.jpg

Quote:

Originally Posted by NorCam (Post 1352362)

Charley,

I don't have any clear pictures right now as I'm rebuilding the computer that all my good reference pics are on. I dug up these two for now and will try to explain what I learned from Mike Thorpe (rszmjt) on the subject of factory issued derby caps. He's handled thousands of these caps and has been checking them since the 1970's for differences between them.

The parts numbers most know for these are 3925801 or 3925805 but they both differ by time frame issued and were also remade by various manufacturers under GM. The early factory originals for 1969 have a double casting rib (or flute) where the screws from the backside of the rings secure to the caps on each of the 4 screw locations. Original production line installed rally wheel caps have this double rib inside, have the GM part number 3925805 and also say made in Canada inside the cap. I think they were made by McKinnon Industries for GM but not positive on that one?

The later versions have a single casting rib (or flute) with one of the above part numbers and in the last 15 years or so, the part number had disappeared completely. They also have various casting flash differences from the factory issued caps or the early over the counter parts but are easy to spot from originals. Below are a couple pictures that simply address the casting ribs, but do not go into the comparisons of the outer fonts and such. I have also been told that 68 and 69 caps differ from each other on the outer beveled edges of the rings where one is more rounded than the other and that the 69 has more pronounced flat edges with a sharper radius.

The later 3925805 part numbers differ widely in the casting flash inside the caps from what is obviously different vendors for GM. They also have different fonts and ring sizes on the outside cap as I have come to learn but still don't know enough about that. I have had 2 sets of originals including a 68 driver with factory issued derby's with the double ribs and made in Canada markings, but quality was poor. Here are two pics showing an original (first pic) and a later cap obviously from GM parts suppliers with the single rib (flute) and various other casting flash markings inside the cap.

http://i1218.photobucket.com/albums/...NKL/Double.jpg
Factory (late) issued cap with clean casting inside cap but no Made in Canada markings.

http://i1218.photobucket.com/albums/...NKL/Single.jpg
Later cap with single rib and likely an over the counter GM part. Notice additional casting flash.

Norcam,
I have some originals (3 non-double fluted and 1 doubled fluted) that are identical to your top photo on my survivor 68 Z.....Did they have two that are factory original??

I haven't seen enough 68 center caps to tell you anything more but any factory original caps that I have seen do have those double ridged flutes. The 68 centers also have a soft rounded outer edge around the edges of the hat, and not the pronounced sharp edge as seen on the edges of the 69 hats.

Maybe post some clear pictures of the ones from your 68 car both inside and out with close up shots from the hats and the return edges?

The largest difference I have found is that the assembly line installed cap have a cone shape to the VERY center on the outside, the caps made for the next run have a rounded dome and the edges are not as sharp.

If you close your eyes and run your finger lightly over the center of the cap you can feel the actual point on the cone, this has been checked on many original cars by myself and or other collectors with survivors and known history.

The first two are the rounded dome shape... the last two have a cone shape - NOTE the reflection in the center and the straight lines versus the curved shape of the reflection in the first two.

I have found that most parts which were subjected to second runs had the parts manufactured from original samples which were polished thus knocking off the sharper edged and lessening the details. the CONE shape makes perfect sense as the original pattern was most likely cut on a lathe.

How many other folks went out to the garage and rubbed their cap cones?