66 BB Plug Shield/heads revisited
Although there are several pieces of good info in the archives, they don't get to a conclusion - two questions remain:
1. Was there a defined time between Feb 66 and June 66 where the shields went away?
2. Did the tapped hole in the heads go away first - does it exist on the late June 66 example that did not have plug shields?
Here are some of the pieces of the threads...
Michael Hanson (4067)
Extremely Frequent Poster
Join Date: January 29th, 2008
Posts: 5,735
65-66 Spark Plug Shields, Again
Well, I spent the evening researching spark plug heat shields for 65-66 big blocks and this is what I've learned. There's absolutely zero consistancy at all and some of the GM information from the print does not apply to the actual part. I just looked at a box full of NOS shields (courtesy, Smokey Yunick) and there were several different versions of this part. Several still have the original part number sticker on them. The 3871266's, that are supposed to have a hole for the mounting screw, had instead, a slot, just like the 1st design shield was supposed to have. There are too many variations in the finished part design to get into here but mostly I learned that almost anything goes as far as trying to decide which would be correct for a certain build date 65 or 66. My 66 has what I believe are the 2nd design 266 with a hole instead of a slot which does not agree with the NOS parts that I've just looked at. Over the years, I've had NOS, some slotted and some with the hole I feel either would be correct for nearly all 65-66 with the possible exception of early 65 buids. I think it's a dead isue and no further research is needed.
Here's the most important thing I learned. I always knew that some time in the 66 model year, the shields were eliminated completely. They were NOT used through the end of 66 production. I always thought this occured near the end of 66 production but I just uncovered information that shows the shields were removed about half way through the model year. Also, in the 66 AIM, the shield, bolt and washer were removed from production on 4 February 66. I think most feel the shield was used to the end of 66 production so it should be interesting to hear from owners of original 66's.
Michael
Joe Lucia (12484)
Beyond Control Poster
Join Date: February 1st, 1988
Posts: 23,237
Re: 1965/1966 big block spark plug heat shields
Michael------
Apparently, these things were made up a variety of ways. The 1965 GM #3868828 are supposed to be 2-1/2" long with a slot in the bracket and a radiused end for the rear of the "cut out" section.
The late 1965 and 1966 GM #3871266 are supposed to be 3" long with a hole in the attaching bracket and a "squared off" end at the rear of the "cut out" section.
Maybe the supplier couldn't get it right.
1. Was there a defined time between Feb 66 and June 66 where the shields went away?
2. Did the tapped hole in the heads go away first - does it exist on the late June 66 example that did not have plug shields?
Here are some of the pieces of the threads...
Michael Hanson (4067)
Extremely Frequent Poster
Join Date: January 29th, 2008
Posts: 5,735
65-66 Spark Plug Shields, Again Well, I spent the evening researching spark plug heat shields for 65-66 big blocks and this is what I've learned. There's absolutely zero consistancy at all and some of the GM information from the print does not apply to the actual part. I just looked at a box full of NOS shields (courtesy, Smokey Yunick) and there were several different versions of this part. Several still have the original part number sticker on them. The 3871266's, that are supposed to have a hole for the mounting screw, had instead, a slot, just like the 1st design shield was supposed to have. There are too many variations in the finished part design to get into here but mostly I learned that almost anything goes as far as trying to decide which would be correct for a certain build date 65 or 66. My 66 has what I believe are the 2nd design 266 with a hole instead of a slot which does not agree with the NOS parts that I've just looked at. Over the years, I've had NOS, some slotted and some with the hole I feel either would be correct for nearly all 65-66 with the possible exception of early 65 buids. I think it's a dead isue and no further research is needed.
Here's the most important thing I learned. I always knew that some time in the 66 model year, the shields were eliminated completely. They were NOT used through the end of 66 production. I always thought this occured near the end of 66 production but I just uncovered information that shows the shields were removed about half way through the model year. Also, in the 66 AIM, the shield, bolt and washer were removed from production on 4 February 66. I think most feel the shield was used to the end of 66 production so it should be interesting to hear from owners of original 66's.
Michael
Joe Lucia (12484)
Beyond Control Poster
Join Date: February 1st, 1988
Posts: 23,237
Re: 1965/1966 big block spark plug heat shields Michael------
Apparently, these things were made up a variety of ways. The 1965 GM #3868828 are supposed to be 2-1/2" long with a slot in the bracket and a radiused end for the rear of the "cut out" section.
The late 1965 and 1966 GM #3871266 are supposed to be 3" long with a hole in the attaching bracket and a "squared off" end at the rear of the "cut out" section.
Maybe the supplier couldn't get it right.
February 2nd, 2005, 04:37 PM 
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