69 BB Hood Insert fit question

[Joe L.]

Re: 69 BB Hood Insert fit question

Okay, after thinking about this for a while, I believe the part numbers changed, but only in a service environment because they now included the speed nuts. (Original production line parts didn't include the nuts.) Joe, do your NOS sets have speed nuts included? If so, that's the reason.

The big question is... Are the CASTING NUMBERS the same between the original 1968 set you have and the NOS sets you have? If they're the same casting numbers, then NOTHING changed (although, as shown in Joe's picture above, something obviously DID change), but if they're different, then yes, they changed, but why?.

Ed

Ed------


The difference in the 2 sets of part numbers was the speed nuts included in the second set. The moldings were the same, at least for any given time. The GM part numbers 3922285 and 3922286 appear on all the moldings, PRODUCTION and SERVICE.

I fully expect that PRODUCTION and SERVICE moldings were absolutely identical, at least if they were both manufactured at the same time. So, I expect that PRODUCTION and SERVICE moldings were the same during at least the 1968-72 period. Sometime after that time something changed. Why, I cannot imagine. I just can't understand why the molds would have changed. It's hard for me to believe that GM would have invested in a new set of molds after the moldings were SERVICE-only pieces and the mold change couldn't have happened prior to the end of their use in PRODUCTION or GM wouldn't have been able to install the moldings on PRODUCTION hoods.

[Edward B.]

Re: 69 BB Hood Insert fit question

Thanks Joe. Since the casting number didn't change, I would imagine the molds never changed either because GM always assigned new casting numbers with mold changes, right?.

I guess this is another one of those mysteries that we'll probably never solve.

And the only way to get a set of moldings that actually fit correctly will be to find an original production line used set that are still in good shape and have them rechromed. Or buy NOS or aftermarket and break out the grinder like I stated before.

Ed

[Joe L.]

Re: 69 BB Hood Insert fit question

Thanks Joe. Since the casting number didn't change, I would imagine the molds never changed either because GM always assigned new casting numbers with mold changes, right?.


Ed

Ed------

In this case, the casting numbers were the same as the finished part numbers. However, casting numbers do not usually change when a mold is replaced unless, of course, the part actually does change in some way. In this case, I don't think the change was intentional.

Very often, there are multiple sets of molds for the same part. Of course, this would not usually occur for a very low volume piece like these moldings.

[Edward B.]

Re: 69 BB Hood Insert fit question

Okay, so going by what we know (or suspect):

1. The original assembly line parts fit correctly, so the molds (and because these were low volume pieces, there was probably only one set, left and right) stayed the same until at least the end of 1972 production.
2. Sometime after 1972 (date unknown), they changed the molds, but didn't change the molding part numbers, so the design was "supposed" to stay the same. "Why" the molds changed is unknown. Maybe the originals got accidentally destroyed or lost??? Who knows! We'll probably never know.
3. The molds DID inadvertently change somehow without Chevrolet noticing it, and all the NOS Service parts sold after the molds changed don't fit correctly. There's a possibility that VERY EARLY Service parts DO fit correctly. It just depends on WHEN the molds changed.
4. The repop parts were probably reverse engineered from NOS Service parts manufactured AFTER the molds changed, therefore, they don't fit correctly either.
5. Someone with a set of REALLY GOOD original assembly line moldings needs to get in touch with Tim at Trim Parts and talk him into reproducing new sets so we 68-72 owners don't have to waste our money and time on incorrect fitting repop moldings!! (Yeah, like THAT'S going to happen!!)

Thanks again Joe. I think we've cleared it up as best we can unless we eventually find the original (and possibly the Service) blueprints. (Ain't gonna happen)

Ed

[Patrick H.]

Re: 69 BB Hood Insert fit question

unless we eventually find the original (and possibly the Service) blueprints. (Ain't gonna happen)

Ed

Part of the GM licensing program is often access to the original drawings. You might be surprised what blueprints are still able to be used.

[Edward B.]

Re: 69 BB Hood Insert fit question

How does one go about obtaining these blueprints? I'm assuming an average Joe Schmoe like me can't get them.

Ed

[Joe L.]

Re: 69 BB Hood Insert fit question

How does one go about obtaining these blueprints? I'm assuming an average Joe Schmoe like me can't get them.

Ed

Ed------


There's no practical way to obtain them. I don't think that these moldings are produced under the GM Reproduction Parts Program although it's possible they are. In any event, licensees who are provided the blueprints are instructed not to release them to others. Remember, this program is not actually run by GM but by some slick outfit in San Diego.

[Edward B.]

Re: 69 BB Hood Insert fit question

Yeah, I didn't think it would be possible.

Thanks Joe

Ed

[Joe L.]

Re: 69 BB Hood Insert fit question

I dug out another NOS set of these moldings I have. One of the boxes is dated 1989 and the other 1990. Of course, that does not necessarily indicate when these parts were manufactured but we do know it was not later than these years. These moldings were better than the NOS set I reported on previously. They still deviate a little from the original 1968 set but I think they would be installable without rework.

One other thing I thought about: since these moldings had a very limited PRODUCTION requirement, it might be that the original tooling was very cheap tooling. GM might not have wanted to invest in expensive tooling for very limited use trim pieces like these. So, it's possible that the tooling required periodic repair and refurbishment with each such event degrading the quality of the finished product.

[Edward B.]

Re: 69 BB Hood Insert fit question

Joe, what was the dates on the NOS set you compared yesterday?

Ed

[Joe L.]

Re: 69 BB Hood Insert fit question

Joe, what was the dates on the NOS set you compared yesterday?

Ed

Ed------


I don't know. There was no date on the box. All I know is that the parts labels have a bar code on them. So, I know they're the most recent of the sets I have.

[Edward B.]

Re: 69 BB Hood Insert fit question

So it does appear they got continuously worse as the years went by. This sort of confirms you theory that the tooling required repairs and/or refurbishments over time. I'd LOVE to find an early NOS set to see how THEY fit. Somewhere in the mid to late 70's or maybe even the early 80's time frame.

Ed