GM T-3 headlights - New info
 

I have always read that the T-3's with the clear triangle (4-bulb system) were used through the end of 67 production, and that the ones with the ribs in the triangle were first used on 68 model year cars and are incorrect for any 67 model year vehicle. (And that's what the 67 NCRS judging manual also says.)

Well, I have proof now that that is not correct. Attached are pictures of an original Ribbed T-3 bulb with date code June 2, 1967 on the back. Date code info copied from the Camaro forum also attached, which shows the stamp decodes as:

62 = June, production line # 2
7 = 1967
2 = 2nd day of month

This is one of the 4 original Ribbed T-3 bulbs in place on the 67 L78 Chevelle survivor that I recently acquired (discussed here: https://www.yenko.net/forum/showthrea...=jeffschevelle )

The car is a late build with 07B trim tag date, so the bulb date is appropriate for the car.

When I got the car I thought it was odd that all 4 of the headlights were Ribbed T-3s on a low mileage car, which would have meant that ALL FOUR headlights got replaced sometime between 68 and 71. So I removed one to check the date, and there it is -- June 2, 1967!!

I will remove the other 3 and check them later to see if any are dated any earlier than this one is. But for now we know that Ribbed T-3's were in the supply pipeline at least by June 2, 1967. Of course there could have been (and probably were) clear triangle bulbs still in inventory and being used in the assembly plants after that date along with the newer ribbed bulbs.

But with this info, NCRS and MCACN judging criteria needs to be updated to allow EITHER version to get full points on a 67 built in June or July of 1967. I am not a member of NCRS, could one of you who is a member post a link to this thread in their judging forum?

Now I have to go buy an NOS set of ribbed bulbs for the L78 elcamino (07D trim tag) we're restoring!! I had 5 sets of NOS ribbed bulbs and sold them all because I believed everyone who said they were not right for ANY 67 !!!!!!!!!

OK Jeff, I just pulled the NON-ribbed T3s out of my 07D Baltimore Chevelle. One illegible, others originals. All are dated June 5th (what's the odds of that?!) line # 1 or 3.

Nice job Jeff, thanks for the info...

So that proves the mixing in of old style and new style bulbs, since my 07B Baltimore has new style bulbs and Bill's 07D Baltimore has old style bulbs

As noted above one of my Ribbed low beams is 62 7 2. The other Ribbed low beam is ?? 7 16 (has no month or line stamp). See pic below. But it is presumably June 16, 1967, since car is 07B.

Both Ribbed high-beams are 61 7 5. So production line 1, June 5, 1967. See pics below.

I texted with Bill, and his clear triangle high-beams are 61 7 5, and 63 7 5, and his clear triangle low beams are 61 7 5, and 6? 7 5 (line # not legible).

So, all that suggests that:

- Production line 2 changed over to Ribbed on or before June 2, 1967.

- Production line 1 changed over to Ribbed on EXACTLY June 5, 1967 (since we have both versions produced on the same date.

- Production line 3 changed over to Ribbed on or after June 5, 1967.

Apparently NCRS has recently picked up on this too! The latest version (7th Edition) of the Corvette Technical Information Manual and Judging Guide is revised that "Although typically clear, late cars may have vertical bars within the T-3 triangle". Thanks Jeff for the great info!!

Great thread on this subject!

My "06D" Fremont Plant built '67 GTO has three of newer '68 style T-3's and one '67 style (left lower). I'm confident these are original to the car, but have not removed them to check any dates.

There is also this "06A" Pontiac Plant built 9800 mile '67 GTO time capsule with the exact same sealed beam configuration as my car.

Whatever you do, don't wash those date codes with soap and water. Some (maybe all) of those stamps are water soluble and may dissapear with washing.

YES!! What he said!

Out of an original 67 Chevelle I am preserving. 04C BAL car.

One low beam is the one with ribs the high beam with without. Same week just different lines.

I know this is great info for our "peace of mind", but what judging organization pulls the sealed beams for date inspection?