3901712 Center Cap question

[Dennis H.]

Hello to all,

I have a set of center caps I've owned probably 20 years. A friend wants them. I know the centers are GM but I'm not sure about the caps. I've searched the forums and based on the info. I've found, I believe they are GM. One of the caps appears to have the remains of a part number sticker. Attached are some pictures. Can anyone give me a definitive answer as to their origin? I will not misrepresent them to anyone.

Thanks in advance for your help.

[Joe L.]

Re: 3901712 Center Cap question

Hello to all,

I have a set of center caps I've owned probably 20 years. A friend wants them. I know the centers are GM but I'm not sure about the caps. I've searched the forums and based on the info. I've found, I believe they are GM. One of the caps appears to have the remains of a part number sticker. Attached are some pictures. Can anyone give me a definitive answer as to their origin? I will not misrepresent them to anyone.

Thanks in advance for your help.

Dennis------


They appear like originals to me. Of course, they could also be GM SERVICE replacements but I know of no way to distinguish between original, on-car caps and SERVICE caps.

[Dennis H.]

Re: 3901712 Center Cap question

Thanks Joe, I just wanted to get another opinion. I don't want to misrepresent these parts to anyone.

[Leif A.]

Re: 3901712 Center Cap question

Dennis,
I agree with Joe. The only difference I see in your center caps and my originals is the colorization. Urban legend has it that originals had a bit of a gold hue to them. Of course, this may have occurred over time...just another insight.

[Richard M.]

Re: 3901712 Center Cap question

I've done some research in the past and have some reference info that may help. I have Original, Service Replacement, and Offshore Reproduction Center Caps. I also have original, restored, and reproduction ornaments. Some I still have, some are gone.

As far as telling the difference between Original and Service Center Caps, I believe that originals did not have labels on the backside, or traces of labels as can be seen where the label adhesive is evident. Every Service cap I see when I open the boxes has a label. I have not seen many Originals so the Label theory is speculative.

Center Caps:

Here are what I believe to be original caps. None had labels or traces of labels.






Original Center Cap and it's Original Ornament before removal. Note the slight goldish hue in the inner annual rings. Also note the font format of the letter "S" in DISC and BRAKES. More on that later.


These are the original screws which held the Ornaments in place. All 4 Caps had ornaments and this type screw.


The 4 Rallye Wheels are "DC" stamped.


For reference these are the original Trim Rings that accompanied this original set.


This is a set of 3901712 NOS Service Replacement Center Caps. Note the large labels on the backsides and from 2 different manufacturers. The boxes are dated a few years apart along with different label text formats.


Here is a comparison of the GM Service Replacement to the Offshore Reproductions. It is difficult to tell the difference from the face of each with the eye but the profile difference can be seen using a gauge. In this comparison I measured the profile of the Reproduction, then placed it over the GM cap. The profile difference can be seen using the gauge in the last photo.

GM left, Repro right(with Repro Ornament attached)

Repro with gauge showing profile.


Gauge profile of Repro set into GM profile. Slight variance.


The backside of each is more obvious. You can see the differences in the capture ring profiles, but when mounted this is unseen.

GM


Repro


Here are more defined photos showing the profiles. Black/old is original. Newer looking is the reproduction.



Another GM NOS showing side profile of capture ring.


Ornaments:

The difference in GM Ornaments to Reproduction Ornaments is more obvious.

The GM to Reproduction has subtle profile differences and a slight variation in shape.

Left GM(rechromed), Right Repro. The slight variance is in the angle of the horizontal face(lettered).


Unobservant by eye however a more obvious difference is in the width and profile of the large outer ring of each and the ring depressed area which is black.

GM(rechromed). Before black paint applied.


Repro. Note the witdth of the raised chrome ring to above, and also the width of the depressed ring for black paint.


Here is a actual measurement showing the widths.

GM


Repro


More obvious..... The Font differences in the letter "S" between the two.

GM(after restoration and black in lettering and adding gold hue to inner annular rings)
Note the curves in the letter "S".


Repro


THere are other characters with subtle font differences but not as obvious as the "S".

GM


Repro


More GM NOS Caps with original ornaments removed from original caps. Gold hue present but hard to see in photos.


For the record, this is not a negative evaluation of the reproductions as it is good they are available. It is mainly to show differences when searching or researching parts.

Rich

[Dennis H.]

Re: 3901712 Center Cap question

Thanks Richard, Based on your description I think all are the GM service replacement. I dug around and found some correct screws. I knew they were wrong but did not know what the correct ones looked like until your reply. I would be interested in hearing more about the caps and the letter "S". Thanks for taking the time to help me.

[Richard M.]

Re: 3901712 Center Cap question

Thanks Richard, Based on your description I think all are the GM service replacement. I dug around and found some correct screws. I knew they were wrong but did not know what the correct ones looked like until your reply. I would be interested in hearing more about the caps and the letter "S". Thanks for taking the time to help me.

Dennis, Yes yours appear to be GM parts. I just added the "S" info to the post as it was growing and didn't want to loose my edits. I lost my earlier first post due to a network glitch somewhere and had to start over.

I feel your caps are GM as well as the ornaments. They don't have a gold hue so I think they may be service replacements. I see most originals have the gold hue, but not 100% sure that they all did. I recently acquired 4 originals and they had the gold.

Rich

[Joe L.]

Re: 3901712 Center Cap question

Rich------


The special screws that retain the ornament to the cap were used from 1967 to 1982. They were once available from GM under GM #3824195. No longer available from GM, they are easily available in reproduction.

[Richard M.]

Re: 3901712 Center Cap question

Rich------


The special screws that retain the ornament to the cap were used from 1967 to 1982. They were once available from GM under GM #3824195. No longer available from GM, they are easily available in reproduction.

Thanks for checking Joe.

Rich
PS I added a few more photos showing the side profiles or GM vs Reproductions in my earlier post.