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02-12-2011, 02:36 PM
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#1 |
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Vintage 4x4s
Join Date: Sep 2010
Location: Prior Lake, MN
Posts: 4,305
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1960's GMC V6 engines
Why were the compression ratios so low (7.5:1) on these engines? As far as I know, the only reason could have been to prevent knock. Was fuel that low in octane back when these V6's were designed?? Anyone know what it was back then? I tried googling it and it was just endless pages of definition of octane and how it is determined. I would love to see a table of octane ratings over time. The higher the compression ratio the more efficient the engine is.
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67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore  )86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6 |
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02-12-2011, 03:17 PM
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One foot in front of the other
 
Join Date: Aug 2008
Location: Parrottsville, TN
Posts: 5,443
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Re: 1960's GMC V6 engines
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02-12-2011, 03:24 PM
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What?
Join Date: Jun 2007
Location: Southern California
Posts: 7,617
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Re: 1960's GMC V6 engines
My thought is for the torque aspect, and that the big block V6's were in trucks.
i.e. slow mover trucks, and low temperature goal, and the grunt.
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Chris 1968 K20 Suburban 1972 K10 LWB PU |
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02-12-2011, 06:15 PM
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its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: 1960's GMC V6 engines
less stress on the engine. The tighter you squeeze something, the more likely it is to pop. Keep the c/r low, and the engine will run longer between compression related issues.
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02-12-2011, 06:25 PM
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#5 | |
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Vintage 4x4s
Join Date: Sep 2010
Location: Prior Lake, MN
Posts: 4,305
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Re: 1960's GMC V6 engines
So what do you guys think about the octane ratings in the 50's and 60's?
Quote:
__________________
67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore )86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6 |
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02-12-2011, 06:41 PM
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#6 |
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its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: 1960's GMC V6 engines
apples to oranges. Diesels (which you hardly saw back then) are build much stronger and heavier. Even the craptastic 6.2 was heavy compaired to a small block.
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