Exhaust Manifold to Exhaust Pipe Distorted-Thread, Flange Nuts

These nuts they are often called “distorted thread lock-nuts” due to the distorted triangular shape of the inner diameter of the threads that you can see in the second image. The original GM part number for these nuts was 3829098. The GM engineering drawing describing these nuts dates from April of 1962. GM changed the design in Feb of 1973. So, these nuts should be correct for model years 1963 thru 1972. These nuts are a very close match to original nuts seen on a NCRS ’66 Bowtie car, shown in the third and fourth images.

If you've ever looked for these nuts at one of the Corvette reproducitons parts companies this is a case where the nuts they sell are obviously not correct. For example, the last image shows the nuts sold by Paragon Reproductions. Notice the raised dots or nipples at each of the six points of the hex. NCRS gurus and knowledgeable judges know that originals did not have the dots. So, don’t bother to buy repros from Paragon since the judges know the Paragon repros are not correct.  Also, the nuts I sell are cadmium plated, not zinc, although they look like zinc. Cad plating will hold up much better than zinc, which is why the nuts taken off the ’66 Bowtie car still look as good as they do. Price for a set of 6 nuts is $22, plus $4.50 to cover the cost of USPS postage in a padded mailer, for a grand total of $26.50.