Hi,
am I correct in assuming the majority of nuts and bolts on my 76 CDV are either UNF or UNC threads of various sizes, with some exceptions i.e spark plugs, pipe threads and electrical connections.
regards Jeff.
Interesting question. 79 was the first time I recall running into metric stuff but I could be wrong. I am just so used to having both metric and SAE that I could have used metric today on my 73 and not noticed.
Metric fasteners started in 77 with the downsizing of the full size GM cars. In 78 it went to the downsized mid-size, and 79 the compacts. As each body was downsized they started using metric bolts. They were painted a flat medium blue to identify them.
My 76 CDV has all SAE nuts and bolts from the factory, no metrics. I've owned this car since January 1977 and no metrics were allowed to be put on it. EAM
I've never encountered a metric bolt yet on my '76 SDV. BUT sometimes accessories that get replaced (alternator, AC compressor, etc.) come with metric threads instead of SAE ones, so unless the car is %100 original you still have to be a little careful.
-Mike Beda
thanks for replies,
Very interesting as it would appear that this was a period of transition for the US automotive industry over to the metric system. managed to clean up my replacement LH exaust manifold threads with a 3/8 UNC tap prior to fitting this weekend.
regards Jeff
For cleaning up threads a 'thread restorer' usually works much better than a tap or die. Taps and dies are designed to cut threads so that is what they tend to do which can be a bad thing if the metal has already been damaged. The restorers have differently shaped teeth so they will tend to try and push the material back where it should be. I finally bought a set a few years ago and they are great. I have not lost any threads since I got it. Usually after using a tap or die you can tell that things are not right and sometimes its difficult to get the nut or bolt to stay tight. Not a problem with the restorer.
Another note DO NOT buy a cheap tap and die set! They are garbage. You do not even get what you paid for not to mention the damage they cause. You should be spending at least $50 on a basic tap and die set. I have not yet seen cheap restorers. The set I have covers like 1/4-1/2" and the similar metrics and was about $50.
sounds like good advice to me TJ,
the treads on my manifold were in fine condition just a light carbon come age related oxidisation, I maybe shouldn't have used the word "managed" in the clean up sense as they were really ok and not in need of restoration.
you're also correct about the buy cheap, pay later, especially with regards to quality tools.
regards Jeff