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GMC Truck Engines And Differences Between The 348 And The 409

10/27/2019
Greg Zyla
Q: Greg, I was reading your column about the 409 Chevy engine where you said that the 348 and the 409 were identical from the outside as both had the "W" cylinder head design. However, I have always been able to tell them apart because the 348 oil dipstick is on the driver's side of the block and the 409 and Z11-427 "W" engines have the dipstick on the passenger side. Also, from 1955 to 1959, did Chevy and GMC use various Buick, Oldsmobile and Pontiac engines in their pickups? M. Scott, Mt. Airy, NC.
 
 
A: You have a keen eye M. Scott and know your "W" head big block Chevy engines very well. Indeed the positioning of the oil dipstick is the only difference to the eye of a 348 and a 409/427 Z11 engine. However, for the sake of buying a 409 that turns out to be a 348, there have been unscrupulous sellers that changed oil pans from the 348 to the 409, and then got away with selling their 348 as a 409.
 
But, fair is fair, and you are 100-percent correct as long as the seller is honest. Finally, there were some 348 truck engines that came with a 409 oil pan as Chevy was mass producing the 409 as the 348 was being phased out. Still, the 348 lasted through the entire year of 1964 in heavy duty trucks and last appeared in 1965 heavy duty truck models.
 
As for the Pontiac engine in General Motors trucks, you are also correct that from 1955 to 1959, many light duty GMC trucks were equipped with the Pontiac V8. GMC utilized the Pontiac engine, which began life as a 287-incher in 1955, in less than 2-ton trucks. Starting in 1956, the 287 received strokes and bores to eventually end up at 389 inches in 1959. The 389 was perhaps the most utilized Pontiac V8 of the era, and its overhead valve V8 that debuted in 1955 was overshadowed by Chevy's 265-inch V8, which is a completely different engine.
 
Finally, from 1955 to 1959, the heavy duty Chevrolet Super Loadmaster V8 truck came with the Buick engine while some Heavy Duty GMCs used an Oldsmobile 370 based engine. Notable were the 1955 through 1957 Chevy school buses that relied on the popular Buick "nail head" 322 cubic inch V8. There are other applications, but too lengthy to write about.
 
You sure did your homework on this question. Thanks much for a look back at GM V8 engines used in the truck and bus lines.

 
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