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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old January 19th, 2023, 03:00 PM
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Default 305E vs 351E design differences

Someone on a Facebook group page asked me what made a 351E engine have that displacement if it was based on a 305E block and the 305 already had the largest diameter piston anyones ever seen at 4.5" across already - he was asking if the 351 had the same diameter piston but maybe just a longer stroke to make more cubes or if it seriously had even larger diameter pistons and if so how big are they?
I do not know whether a 305 and 351 share a block with different bores, or both are unique, or if the pistons are bigger in the 351E vs 305E or what makes a 351 a 351 vs a 305. I assume the heads or valve sizes in the heads are likely also different between the two engines, and I do know about the exhaust manifolds and carbs / intakes being different but don't know about what is different inside one really.
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Old January 19th, 2023, 06:15 PM
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Default Re: 305E vs 351E design differences

Nut:
I'll take a crack at your question. Others feel free to embellish.
* 351e is a magnum with bigger valves, bigger intake and exhaust ports.
* 351 has larger bore than 305. I believe it's 4.25" for 305 vs. 4.5" for 351.
* 351 has steel crank vs cast crank in 305. Unsure about stroke?

Hope that helps.
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Steve
New Orleans
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Old January 19th, 2023, 11:20 PM
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Default Re: 305E vs 351E design differences

All blocks 305-478 are the same size. 305 has the smallest bore at 4.25". 351 is 4.56" and 401 is 4.87". All have the same stroke, 3.58". The 478 has a 5.125" bore with a 3.86" stroke. The 379 and 432 are a stroked 351 and 401 respectively.
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Old January 20th, 2023, 12:51 AM
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Default Re: 305E vs 351E design differences

Quote:
Originally Posted by Prowbar View Post
All blocks 305-478 are the same size. 305 has the smallest bore at 4.25". 351 is 4.56" and 401 is 4.87". All have the same stroke, 3.58". The 478 has a 5.125" bore with a 3.86" stroke. The 379 and 432 are a stroked 351 and 401 respectively.
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Old January 22nd, 2023, 07:21 AM
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Default Re: 305E vs 351E design differences

Quote:
Originally Posted by sclor View Post
Nut:
I'll take a crack at your question. Others feel free to embellish.
* 351e is a magnum with bigger valves, bigger intake and exhaust ports.
* 351 has larger bore than 305. I believe it's 4.25" for 305 vs. 4.5" for 351.
* 351 has steel crank vs cast crank in 305. Unsure about stroke?

Hope that helps.
Regards
Steve
New Orleans
Correct, except the 351E and certain other late 351's have cast cranks. Stroke is the same for the 305, 351, 401, and 702 as others have pointed out.
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