C3 headlight assembly differences

[Robert W.]

I recently purchased a set of headlight assemblies for a C3, they were cheap and I couldn't pass them up, yet I don't know what years they will fit.

( My 68 has the highly popular, owner installed "headlight delete" option, musta looked pretty cool back in the early seventies, looks like crap now ! ).

Now I need to determine what model years these assemblies fit and if they will work for a 68. It is my understanding that 68 used a slightly different assembly with a smaller opening in the hood surround. I have searched the archives and found only discussions on the bezels.

These are complete and have fiberglass bezels. I have not found any visible markings, p/n, dates, etc. without disassembling them. Can anybody shed some light on the differences throughout the years and what to look for ??

Thanks in advance

[Lynn H.]

Re: C3 headlight assembly differences

The headlight support is the piece you have to be most concerned with, although the door is somewhat smaller on some 68's. There is the support that is correct for 68-72, which would be 100% correct for your car. Then the 73-77 support, which was the service part for the earlier cars. Requires the use of a spacer in the front due to the rubber bumpers. Then the 78-82 support is a whole different piece. If you had some good photos I could probably tell you what you have, but the fiberglass bezels did not start until 73. I have some NOS pieces of the two earlier versions I can post photos of for you tomorrow if you still need them.
Lynn

[Grant W.]

Re: C3 headlight assembly differences

I recently purchased a set of headlight assemblies for a C3, they were cheap and I couldn't pass them up, yet I don't know what years they will fit.

( My 68 has the highly popular, owner installed "headlight delete" option, musta looked pretty cool back in the early seventies, looks like crap now ! ).

Now I need to determine what model years these assemblies fit and if they will work for a 68. It is my understanding that 68 used a slightly different assembly with a smaller opening in the hood surround. I have searched the archives and found only discussions on the bezels.

These are complete and have fiberglass bezels. I have not found any visible markings, p/n, dates, etc. without disassembling them. Can anybody shed some light on the differences throughout the years and what to look for ??

Thanks in advance

Hi Robert

For your 68
There is an early design small headlight doors and a later 68 design same size as the early 69's
The difference is in the headlight adjustors for 68 which are rounded. 69 and up are pointed.
The headlight support is also different. 68 to 72, 73 to 77 and 78 to 82
Find the part number on the headlight support and I will tell you if you got a steal if it is for a 68 to 72.
68 used the metal headlight bezel. If you have fiberglass then they could have been replaced at one time or if original off a car then you have 78 style.
First of all you have to determine if you car is early or late.

Thanks, Grant

[Robert W.]

Re: C3 headlight assembly differences

Here are some pics, let me know what you think.

[Grant W.]

Re: C3 headlight assembly differences

Hi Rob
I think this came off a 75 to 78 to 82. If you can get the part number off the top of the support. Just behind the pod.
Also you can you see the back corners of the headlight door is a late design. The corners are concaved in. 68 to 73 and up to 75 has the corner filled in.
Again do you have an early or late 68.
Thanks, grant

[Robert W.]

Re: C3 headlight assembly differences

Build date of Feb 22, 68. vin 12034,

what determines early or late? does it vary with each individual change they made or is it determined by a set date?

[Robert W.]

Re: C3 headlight assembly differences

I inspected the assemblies a little closer, amazing how the smallest amount of dirt can hide a p/n.

I found p/n 347890 with a date code of 76, seems to be a RH support for a 75-82.

[Grant W.]

Re: C3 headlight assembly differences

Hi Robert
The headlight door your bought is correct for a 73 to 77.
Early cars would be Sept 67 to Jan 68 Some say early includes Feb but I'm not sure. Maybe someone else with Feb cars can chime in.
Does the current headlight door you bought fit the headlight top surround of your car, if it hasn't been butchered. If that headlight door fits with about 1/16 spacing around the headlight door then you need the later style 68 headlight doors.
Thanks, Grant

[Joe L.]

Re: C3 headlight assembly differences

I inspected the assemblies a little closer, amazing how the smallest amount of dirt can hide a p/n.

I found p/n 347890 with a date code of 76, seems to be a RH support for a 75-82.

Robert-----


As you've found, the headlight SUPPORT(i.e. "U-shaped" frame) assembly is for a 1975-82 Corvette. It's not the correct piece for any 68-74 Corvette.

However, many of the remaining parts of the complete headlight assembly will work for a 1968 IF the 68 is a later 1968. This includes the HOUSING assembly (i.e. the part that includes the door).

Just when the 1968 changeover occurred, I do not know. But, it doesn't really matter. All you need to do is to measure your headlight opening in the upper surround. If the front-to-rear dimension is 10-3/16" and the side-to-side dimension is 15-5/16" (although I think the side-to-side dimension is the same for both early and late 1968), then you have the later 1968 configuration and that's the same as 1969-82. In that case, you can, at least, use the housing and most of the other parts from the 75=82 assembly you have.

If you have smaller dimension(s) than I've described above, then you have the early 1968 design. In that case, you can't use the housing or the support, but you could use most of the other parts, not that it really matters because the housing and the support are the most expensive parts.

The 1968-74 supports are reproduced and available. The L1968-82 housings are also reproduced and available. Although not inexpensive, you can get them new. You can also purchase complete, rebuilt assemblies which include, basically, everything you need for about 500 bucks per side.

However, the above only applies if you need the LATE 1968 to 1982 assemblies. If you need the EARLY style, that's a different story.

[Lynn H.]

Re: C3 headlight assembly differences

The headlight support is the piece you have to be most concerned with, although the door is somewhat smaller on some 68's. There is the support that is correct for 68-72, which would be 100% correct for your car. Then the 73-77 support, which was the service part for the earlier cars. Requires the use of a spacer in the front due to the rubber bumpers. Then the 78-82 support is a whole different piece. If you had some good photos I could probably tell you what you have, but the fiberglass bezels did not start until 73. I have some NOS pieces of the two earlier versions I can post photos of for you tomorrow if you still need them.
Lynn

I had first listed the dates of the supports as 68-72, 73-75, and 76-82, and then changed my mind (I was too lazy to look it up at the time). I think I was right the first time. I will take a couple photos of the three different supports and post them.
Lynn

[Joe L.]

Re: C3 headlight assembly differences

I had first listed the dates of the supports as 68-72, 73-75, and 76-82, and then changed my mind (I was too lazy to look it up at the time). I think I was right the first time. I will take a couple photos of the three different supports and post them.
Lynn

Lynn-----


Different part numbers were used for the 1968-72 versus 73-74 supports. However, as far as I know, these were all functionally interchangeable. So, one could use a 1974 support on a 1968 and vice-versa. The 68-72 supports were GM #3915681 and 3915682. The 73-74 supports were GM #331825 and 331826. I don't know how the 2 pairs of supports differ but, as I say, I believe them to be functioanlly interchangeable.

For 1975-82, the pair of supports were the same for all years and not directly interchangeable with earlier.

There was also a pair of SERVICE-only part numbers for the 1968-74 supports. These were GM #6258533 and 6258534.

And, there was a SERVICE-only pair of supports for 1975-82. These were GM #14084417 and 14084418.

[Lynn H.]

Re: C3 headlight assembly differences

Lynn-----


Different part numbers were used for the 1968-72 versus 73-74 supports. However, as far as I know, these were all functionally interchangeable. So, one could use a 1974 support on a 1968 and vice-versa. The 68-72 supports were GM #3915681 and 3915682. The 73-74 supports were GM #331825 and 331826. I don't know how the 2 pairs of supports differ but, as I say, I believe them to be functionally interchangeable.

For 1975-82, the pair of supports were the same for all years and not directly interchangeable with earlier.

There was also a pair of SERVICE-only part numbers for the 1968-74 supports. These were GM #6258533 and 6258534.

And, there was a SERVICE-only pair of supports for 1975-82. These were GM #14084417 and 14084418.

Like always I get confused on exact dates for interchangeability, if I do not take the time to look things up. Here is a couple of photos of the three different ones as I "think" I know them to be.
In the first photo it shows the 68-72 support at the front left. The back left piece is NOS (P/N #6258533) which I am referring to as the 73-75 piece. You can see the instructions and the spacers (in the bag) that were included with these in service for use with the 68-72 cars You needed to add the spacers because of the change in the front bumper. The piece on the right is the 78-82 support.
In the other photo, the one on the left is the 78-82 support. The middle the 69-72 original style support, and the one on the right is the NOS 73-75 support.
I think if you look closely at the configuration of the "arms" of the supports you can easily distinguish them from each other.
Lynn

[Dennis D.]

Re: C3 headlight assembly differences

Original out of a 70 left photo). Compared to the photo provided, (right photo)

To add to Joe's comments.... I understand the difference in the 68-72 and 73-74 support. The interesting thing is that the service replacement for 68-74 has a different part #. As far as I can tell, the only difference in the service replacement,(compared to the 73-74 version), is the spacer block/instructions. I would say the support is a 73-74. Is the replacement part number embossed on the support and just printed on the box?

[Lynn H.]

Re: C3 headlight assembly differences

Original out of a 70 left photo). Compared to the photo provided, (right photo)

To add to Joe's comments.... I understand the difference in the 68-72 and 73-74 support. The interesting thing is that the service replacement for 68-74 has a different part #. As far as I can tell, the only difference in the service replacement,(compared to the 73-74 version), is the spacer block/instructions. I would say the support is a 73-74. Is the replacement part number embossed on the support and just printed on the box?

The 73-75 part is physically different from the earlier 68-74 version. That is why you must use the spacers for the later support to work in the earlier cars. You have to look closely at the arms on the supports, and if you look at the photos I posted you can see the difference in all three supports. They are all three different, that is why they all three have different part numbers. It is not a situation where they just changed the number on the box, the piece itself is different. When the part changed in 73, it became the only part available for service of the 68-72 cars, with the use of the spacers.
Lynn

[Joe L.]

Re: C3 headlight assembly differences

Original out of a 70 left photo). Compared to the photo provided, (right photo)

To add to Joe's comments.... I understand the difference in the 68-72 and 73-74 support. The interesting thing is that the service replacement for 68-74 has a different part #. As far as I can tell, the only difference in the service replacement,(compared to the 73-74 version), is the spacer block/instructions. I would say the support is a 73-74. Is the replacement part number embossed on the support and just printed on the box?

Dennis------


The 73-74 supports were never available in SERVICE under their original part numbers, GM #331825 and 331826. Instead, they were the ones supplied under SERVICE-only part numbers GM #6258533 and 6258534. Why? Because these part numbers define, basically, a "kit" which includes the 331825 and 331826 supports PLUS the hardware to adapt them to the 68-72 applications.

When I used the term "functionally interchangeable" with respect to the 1968-72 and 73-74, I did not mean that the 2 pairs were identical. If they were identical, there would not have been a changed part number for 73-74. However, if someone has a 68-72 and needs a new support (or a complete assembly), they can use a support from a 73-74 by also using the shims (easily fabricated). In fact, since late 1973 and until they were discontinued, that's exactly what one would have had to do if they had purchsed a NEW support from GM for a 1968-72 (although the shims were included with the SERVICE parts).

I did not get into all of the above in my original responses since the "thrust" of the question was relative to what year headlamp assemblies would work for a 1968. That is what I focused on rather than "correct in every nuance of detail".

Now, one more thing anticipating someone's question: we know that the 73-74 supports can be used for 1968-72 (i.e. rearward compatibility). However,
can a 1968-72 support be used for a 1973-74 (i.e. forward compatibility)? I believe the answer is yes, but they have to be slightly modified. I've never done it, though.