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#49121 - 04/07/09 10:53 AM Factory Torq and Horsepower GMC Six 248-270-302?
DeuceCoupe Offline
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Registered: 04/17/06
Posts: 529
Loc: Northern CA
I've been following the Nicson and other posts and trying to learn about the GMC Six and add it to my computer and dyno database.
I have a lot of car manuals but very little truck info.

Would anyone be able to post factory torq and power ratings (gross or net or both!) for the GMC sixes
228-236-248-256-270-302?

Any or all would help, searched all over the web and couldnt find this info.
Thanks very much
DeuceCoupe

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#49123 - 04/07/09 11:31 AM Re: Factory Torq and Horsepower GMC Six 248-270-302? [Re: DeuceCoupe]
Ron Golden Offline
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Registered: 11/09/06
Posts: 217
Loc: Kansas City, Missouri
I found some info at Old GMC Trucks.com. You'll have to do a lot of looking thru their pages and tech info. I'll do some more looking to see what I can find. We have quite a few old tech books, motor manuals at the shop.

228 cid
HP: 100 @ 3400 rpm
TQ: 182 @ 1200-2000 rpm

248 cid
HP: 114 @ 3600 rpm (125 HP also listed for later models)
TQ: 202 @ 3400

Ron

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#49127 - 04/07/09 03:55 PM Re: Factory Torq and Horsepower GMC Six 248-270-302? [Re: Ron Golden]
chevman32 Offline
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Registered: 03/16/05
Posts: 58
Loc: Sanger, Ca.
My 1954 GMC pickup has a plaque that states the horsepower of sthe 248 at 118. Torque is not mentioned.

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#49134 - 04/07/09 05:52 PM Re: Factory Torq and Horsepower GMC Six 248-270-302? [Re: chevman32]
JasonS Offline
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Registered: 01/13/01
Posts: 129
Loc: southeast SD
302 1952-54: 145@3600 ; 262@1200 7.2:1CR

302 1955: 155@3600 ; 268@1400 7.5:1CR

302D 1955: 155@3600 ; 268@1400 7.5:1CR

302 1956-59: 160@3800 ; 268@1600 7.5:1CR

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#49136 - 04/07/09 08:53 PM Re: Factory Torq and Horsepower GMC Six 248-270-302? [Re: JasonS]
DeuceCoupe Offline
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Registered: 04/17/06
Posts: 529
Loc: Northern CA
All,
This is helping a lot!
I am searching the web for old carb sizes, next need to hunt for compression, valve sizes (big head vs little head), and cam specs (as if).

Please continue to post any other easy tidbits of info you find, it all comes together like a jigsaw puzzle eventually.

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#49139 - 04/08/09 05:53 AM Re: Factory Torq and Horsepower GMC Six 248-270-302? [Re: DeuceCoupe]
don 1450 Offline
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Registered: 09/21/01
Posts: 510
Loc: Indianapolis, Indiana USA
From the GMC Maintenance Manual 1955-1959:

270A 130 hp @ 3400 rpm

270B 140 hp @ 3400 rpm

302 160 hp @ 3400 rpm

God's Peace to you.

d
Inliner #1450

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