[LS6 RAT]

RS69,

There are 2 GM camshafts that have been used for 1965 thru 1971 solid lifter high performance big blocks. And there has been a fair amount of confusion as to their applicability to which RPO option. The two camshafts are 3863143 and 3904362. My understanding is that 3863143 was used originally with L78, L72 options during the model years 1965 & 1966. Camshaft 3904362 was used originally with L71, L72, L78, L89 & LS6 during the model years 1967, 1968, 1969 1970 & 1971.

Where the confusion exists is that camshaft 3904362 was used with the re-designed oiling system incorporated with the 1967 and later big block. This camshaft (3904362) was discontinued shortly after the last high performance big block, the 1971 LS6 option in Corvette.
GM issued the earlier 3863143 camshaft to be the service replacement unit for all applications using the original 3904362 camshaft. There was a one way relationship between these two cams. 3863143 could be used in '67 and later blocks, although a GM technical bulletin was issued recomending a modification to be performed before installing this cam in a '67 & later block. However, camshaft 3904362 should never be used in '65 & '66 year blocks, because a oil starvation condition would occur, since this camshaft did not incorporate the grooved rear journal necessary along with the grooved cam bearing that was part of the earlier blocks oiling design. Hence the decision to discontinue the 3904362 camshaft to prevent catastrophic failure due to incompatibility of the two cams between the two re-designed cylinder cases.
Further confusion abounds because the GM parts books and Colvins books show incorrect part numbers for some of these applications. An example would be the 1953 thru 1971 Corvette parts book, this shows camshaft 3863143 as the part for a LS6 application. Another example is Colvins book, which shows 3863143 camshaft as the part for a 1969 L71.

In some applications camshaft 3863143 & 3904362 are shown with the same specifications, while other applications show 3863143 to have different specifications. I think most on this board think these cams are identical except for the groove, I am not sure this is true.

Specs for 3863143 & 3904362 have been shown to be .520 intake lift, .520 exhaust lift, 316 intake duration, 302 exhaust duration.

Camshaft 3863143 specs for 1965 are also shown as .497 intake lift, .503 exhaust lift, 348 intake duration, & 348 exhaust duration.

Camshaft 3863143 specs for 1966 are also shown as .520 intake lift, .520 exhaust lift, 336 intake duration, & 336 exhaust duration.

As you can see there is some conflicting information out there. I also believe that Cranes "blueprint series" cams are not exactly the same as GM's, they are close, but I would suspect that Crane, as well as any other manufacturer would improve upon the GM's specs, as camshaft technology has obviously advanced since the 35 years of the previous design.
I have had both of the above camshafts, NOS, however I did not take them to someone knowledgeable to do a comparison. I have since sold the 3863143 cam and kept the 3904362, as I believe this is the true original GM camshaft used in production LS6 engines, which I have 2 of.