I'm just wondering what year it was when the indent for the vacuum and headlight harness was moved from the drivers inner fender area over to the rad support. I'm guessing that the 69-72 models had the indent in the inner fender and that starting with the 73 model year, the inner fender was smooth, with the indent now being in the rad support...correct?
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Re: Quick C3 rad support question.
Greg-----
Yes, that's correct. The GM #339176 radiator support came into use in 1973 for ALL Corvette applications and continued to be used for all Corvette applications through mid-1976. This is the support with the "cut out" for the wiring harness/vacuum hoses.
In March, 1974 the late 1969 through 1972 radiator support for big block applications except L-88 and ZR-2, GM #3966596, was discontinued from SERVICE and replaced by the GM #339176 for all 1969 through 1972 big block applications except L-88 and ZR-2.
The reproduction radiator support available today is, essentially, a reproduction of the GM #339176 radiator support and not the GM #3966596. The 339176 is the PRODUCTION and SERVICE support for all 1973 through mid 1976 Corvettes. It is the SERVICE support for 69-72 Corvettes with big block, except L-88 and ZR-2. The left side relief is the primary difference between the 3966596 and the 339176 supports, although there are a few other differences involving holes, etc.In Appreciation of John Hinckley -
Re: No cut out in 73 Radiator Support
Gregg and Joe The 73 inter fender is a one year part drivers side. Their is a hole for the wiring harness/vacumn hoses to pass thru. Also the coolant bottle area has a 73 only shape so later bottles don't fit and was the first year for this type bottle. The radiator support on the whole model year was straight on the drivers side with no cut out. This is the way all in my collection are early or late in the model year. LyleLyle
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Re: No cut out in 73 Radiator Support
Lyle-----
If that's the case, then the specifications for the GM #339176 support must have changed after 1973. The 339176 was definitely the support used for 1973. The NOS examples of this support that I have do have the "cut-out" for the harness/hoses. However, I'm certain that these were manufactured after 1973.
This being the case, I wonder what the differences were in the original 1973 GM #339176 support from the earlier support used for 69-72 big block Corvettes? I thought that the "cut-out" was the only significant difference between the 69-72 and 73-76 supports and was the reason that the part number changed.In Appreciation of John HinckleyComment
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Re: No cut out in 73 Radiator Support
Joe I have been buying used units for years and I have had to change the width of the supports for the lower radiator. The length of the metal between the supports. I also look for weld nuts on the center two holes. I have no idea what they were on only that I can make them so they appear they were allways on a 73. I have never bought any with the cut-out. LyleLyle
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Re: No cut out in 73 Radiator Support
Well thanks a lot guys for clearing up this support issue for me. At least now I am sure that my car should not have this cut-out and which years should be the same as my 69.Comment
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Re: No cut out in 73 Radiator Support
Greg and Lyle-----
Basically, all of the L69-72 radiator supports used the same frame section. The differences were in the brackets welded to the bottom of the support and/or the "width reduction" plates welded to the sides of the frame opening. The following are the "basics" for the 4 supports used:
1) small block with aluminum radiator----two brackets with "cup" recepticles for retention of the lower "pins" of the aluminum radiator are welded to the lower rail section of the frame. "Width reduction plates" welded to both sides of the frame create an opening which is 22-3/8" wide;
2) big block with aluminum radiator (L-88/ZL-1/ZR-1/ZR-2 only)----same as above except "width reduction plates" create opening which is 24-3/8" wide;
3) big block with copper brass radiator (all except above)-----u-shaped brackets welded to bottom rail of frame with 28" on center spacing. NO "width reduction plates" welded to side of opening;
4) small block with copper brass radiator (all with THM and/or C-60 and most L-46 and LT-1) u-shaped brackets welded to bottom rail of frame approximately 26-1/2" on center spacing; NO "width reduction plates".
All of tha above supports have holes and weld nuts on the top section of the support for the center-mounted fan shroud bracket used with the copper/brass radiator regardless of whether the particular support is for one of those applications, or not.
The 69-72 supports for aluminum radiator applications also have holes and weld nuts on the top frame rail for attachment of the center-mounted, upper radiator support bracket. I think that the original supports for the copper/brass radiator cars also have these holes and weld nuts (unused, of course), but I'm not sure of that. It would be interesting to hear from someone with a known-original 69-72 with copper/brass radiator on this point.In Appreciation of John HinckleyComment
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