Just received the June issue of BCM, lo & behold, there's an article on the original
"Sports Car of Buses", the 4106, beginning on pg 30. Way cool, for us GMC folk. (And a hearty shout-out to Geoff, Pete, and the others who own the second-generation "Sports Car of Buses", the RTS!
There are a few facts in the article that are inaccurate, something that only a GMC nut (such as myself) would pick up, but should be corrected:Original Tire Size:
From the factory, they came equipped with 11.00 x 20 tube-type bias ply all around, a tire that turned 495 revs/mile. Many owners have switched to either 22.5 or 24.5 wheels and tubeless tires, due to better availability and safety.Engine Power Output:
The 8V71 in the 4106 came stock from the factory with N60 injectors. Initial governor setting was for 1650 rpm, later upped to 1800, and then to 2100 in the last years of production. Depending on what vintage literature the data is gleaned from, the power is either 235 @ 1650, 253 @ 1800, or 277 @ 2100. Naturally, due to the "Tim Allen Home Improvement Syndrome", we all prefer the 277 figure!Fuel Tank Size:
Stock was 140 gallons, but there was an optional (and very rare!) 165 gallon tank available.Bulkhead Cracking Problems:
Based on field unit failures, and subsequent warranty repairs, GMC made running production changes on the engine bulkhead in late 1962, as well as a retrofit kit for units already in service. It is still an area of concern, especially if the coach has been retrofitted with an automatic transmission. Inspect it closely, preferrably over a pit.Photo Caption on Pg 31:
Top to bottom, a 3751 "Silversides", a 4104, and the rest are 4106s. There is NO 4103 or 4107 pictured.
HTH & FWIW. . .