Here's a tough one. I got a motor here with a CLU code on the block. Casting #3970010.
I cannot find this code in the 69-72 Motors manual, or the Chevelle by Numbers book. The casting # indicates it is possibly a 71' 350 Hi-Perf. 4 Bolt, which is, as I'm told it is supposed to be. Or a 68' 327. The casting # info does appear in the "By Numbers" book. But these casting numbers can vary 10+ years. Can anyone shed some light here on the CLU code? I would like to validate the code before I purchase the motor.
Thanks for any help anyone can supply.

C-b-t-N, 1970 thru 1975, page 62, code CLU, 1973 passenger only, 350/145 horsepower, TH350, wagon. No other year or model listed.

010 blocks were produced for many, many years, are the default 350 block, and were made with either 2 or 4 bolt mains. Not an unusual or special block.

There are two C-b-t-N books, 1965 thru 1969, 1970 thru 1975. Colvin is working on a book from 1955 thru 1964 now, but it will not be done for at least another year, way too much to cover. May end up two books.

Might look on the back of the engine, just below the manifold, on the bell housing flange for a date code. Something like A203 with a screw looking deal on each side. The last number is the year of casting. In the one I posted it would be Jan, 20, 1973 for the 010 block with three digit suffix. Hard to read these sometimes though.

Thanks guys, I will investigate the date code also. If anyone else has any other info contrary to these findings, let me know.

I-man

I purchased the Chevrolet b t n today from local Chevrolet dealer parts dept. Got an excellent deal on the 65-69 and 70- 75 books reg $29.95 got @ list for $22.95 ea + tax. I believe that a 55 -64 book is already in print as I saw three books on display. I didn't look @ it, but it had the year 55 -? on it. Can someone also verify this book exists?

It is two different books, one 1955-1959 and the other is 1960-64. The 1960-64 is in print and has a white 1962 409 car on the cover.I've had my 60-64 copy for about a year now, but have not seen the 55-59 yet, but it is advertised as available.

Neat books. I'll have to contact Alan and see where my copies are. Thanks for the "seen one" info.