Hello Chaps, I am wanting to rebuild my GMC 1943 270 engine, I have heard that you can get them bored out to 298, does any body know a supplier of pistons and rings, I want to get all the parts together before shipping the engine off to the machine shop. thanks Howard.
To get 288 cubic inches from a standard stroke 270 (4" stroke) would require an over bore of 1/8" (0.125") I don't think there's enough cylinder wall thickness to get 298 from the same block. A piston that big gets into the category of extremely expensive custom forged items. Assuming you can find someone to build one that size (Venolia, perhaps?) be prepared to spend upwards of a thousand dollars for six pistons. Then you'll have an engine suitable only for racing. It would be a lot simpler to try to find a GMC 302 engine instead of modifying the 270. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Hello Jerry, thats very helpful and thank you for the advice, finding a 302 over here in the UK may prove very hard. I will have to give this alot of thought what to do next. Thanks Howard
270 engines powered untold thousands of WW II military trucks- - - -there's no real reason to upsize the displacement. Since most of those engines were used, abused, and scrapped by dirt track racers and Bonneville land speed record attempts in the 1950's and 60's, there are very few engines and/or rebuilding parts still available. If the engine needs to be rebored due to cylinder wear, it might be more cost-effective to sleeve all six cylinders back to whatever bore size you have currently, and re-use your pistons. Piston rings are much more available than replacement pistons- - - -just "thinking outside the box!" Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I am a little surprised that parts and engines for 270's and possibly 302's are not readily available in Europe or the UK. Perhaps less 302's (being a later engine) than 270's but it seems that there are several vendors located across the pond that offer military surplused and remaining stores of surplus supplies and parts that may have been gobbled up by enterprising vendors. My understanding is that much of the spares were left behind after the war because of the cost and space to transport surplus and spare military parts back to the USA.
When I was stationed on Okinawa in the 1970's, there was a huge business involved in dismantling and scrapping Southeast Asia surplus equipment- - - -"deuce and a half" frames and other parts stacked 10 deep or more waiting to go through a shredder. Those trucks eventually made it back to America- - - -behind badges that read "Datsun", "Toyota", etc. It's possible that those WW II GMC's got home with labels like "MG", Triumph", "Fiat". "Mercedes", etc.! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
During WWII, GMC made nearly 600,000 trucks with the 270 engine. Most went overseas, and many of those continued to serve various NATO countries thru the Cold War era. As the US transitioned to more modern vehicle designs in the early 1950s, nearly all of the GMC spare parts were sent to European allies in support of these vehicles.
Consequently, there are literally tons of parts available on that side of the pond. Several years ago, one of the vendors I talked to purchased the stock of a competitor that was retiring. He told me that he moved over 20 tons of parts to complete that purchase. I read someplace else where a guy purchased several crates containing 80 brand new crankshafts. Many places have NOS pistons, rings, connecting rods, bearings, rocker shafts, valves, valve covers, etc. etc. A lot of this stuff is still sealed and packed in cosmoline, with dates from the early 1950s.
If your goal is just to rebuild, then I would not bore any larger than the recommended 0.060". If you are looking for stock pistons, they show up on the various auction sites quite frequently, as do rings. Just do search on "CCKW" and "270", or "DUKW" and "270". If you find a vendor with a variation of the part you need (i.e. 0.040" over pistons), shoot them a message as they may have what you are looking for. It is worth noting, that the stock WWII era 270s had very low compression ratios - like in the neighborhood of 6.75:1. Not sure if that would be a factor for your build or not.
If your goal is more performance oriented, then as Jerry suggests, I would start looking for a 302. All of the postwar GMC 2 - 1/2 ton trucks had them (M-211 & M-135, for example). A lot of them got left in Europe as well. This series of trucks tends to be shunned by military vehicle enthusiasts, so they can usually be picked up for a reasonable price.
Best Regards
Last edited by CrowbarBob; 06/17/20216:47 AM. Reason: Typo: 800,00 should have been 600,000
