I have several 45 engines. One of them has a bad cam cover. I found one on ebay for a good price and bought it. It seems to be missing one of the index holes that locate it to the engine case. So I got to looking at it and noticed that the casting # is different then the other. The one that I'm trying to replace is numbered 131-372. The ebay one is 25202-37. Bruce Palmers book is confusing to me but I think it says that the -37 is for a big twin flathead. The two covers look virtually identical except for the missing hole. Could they possibly be the same size? I would have thought that the big twin one would have been bigger.

 

Welcome to the forum, Jim. Page 190 of Palmer mentions three BT SV gear covers over the 1937–48 period. One has casting number 131-37, is smooth on the outside so it has no ribs and it was used on most, not all, engines 1937–39. Second cover is smooth and was used for 1937–39 Model UMGs for the NYPD. I’m not sure of the casting number for the second cover but it has no hole for a timer. Third cover has casting number 131-40, has horizontal ribs on the outside and was used 1940–48. None of these three covers is relieved to clear the front exhaust pipe because no relief was necessary due to the way the pipe was routed.

For 1937-later 45” SVs Palmer mentions three gear covers on page 198 but he says they all have casting number 131-372. However, and as you have discovered, at least one other casting number was employed: 25202-37. Late last year I emailed Bruce about several things including this second casting number and although he replied to eight of my emails he didn’t get around to addressing 25202-37 so I can’t say for sure when it first appeared. Some, not all, of these second covers have casting date codes and the earliest I’ve seen is 7 58 indicating casting in July 1958. Other date codes I’ve seen on these second covers include 10 8, 12 9, 8-60, 9-60, 10 60, 5 61, 4 62 and 7 63. The latest date code I’ve seen on them is 122172 which I take to indicate casting on December 21 in 1972. Covers with casting number 131-372 are relieved at the front to allow clearance for the front exhaust pipe. Covers with casting number 25202-37 have the same clearance for the same reason so they too are a 45” cover not a BT cover. I can’t explain the difference regarding the holes you mentioned.

Bruce is currently working on a new book which will contain corrections and improvements as well as extra info in several areas. He told me last year that the additions were increasing the book size by 100 pages but I heard recently that further pages may now be included. Apparently he was hoping for a Christmas release but that seems to have been delayed although I am not sure when the new book will be available.

Please send me a PM and I'll give you some other info.
Eric

 

Thanks Eric. I didn't know Palmer was doing another book. Have to keep watch so I can order it. I'd like to send a PM to you but haven't figured out how yet.