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Old March 9th, 2010, 07:19 PM   #1
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Default Telling the difference between a 305 and 350

Is there a way to tell the difference between a 305 5.0L and a 350 5.7L? Obviously other than casting number and the VIN (the engine was swapped)

Just courious if there was a way, i'm pretty sure that they 305 and 350 use the same block just smaller bore and stroke....or something like that

Thanks
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Old March 9th, 2010, 07:46 PM   #2
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casting numbers is pretty much it.
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Old March 9th, 2010, 08:06 PM   #3
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On the older ones, the 305 had a wider harmonic balancer. But, I've seen a few 350 crate motors and GM remans that had the wider balancer on them.
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Old March 9th, 2010, 08:10 PM   #4
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305s , 350s are internal balanced. 400s are external balanced

Last edited by Yetti; May 2nd, 2010 at 07:54 PM.
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Old March 9th, 2010, 08:24 PM   #5
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The 305 is internally balanced.
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Old March 9th, 2010, 08:37 PM   #6
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If it's 86 or newer, the displacement is cast in the drivers side below the head by the bellhousing. When they went to a 1 piece seal, they all turned to external balance on the flexplate. Before that, only the 400 was external.
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Old March 9th, 2010, 08:47 PM   #7
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Quote:
Originally Posted by jbsjunk View Post
If it's 86 or newer, the displacement is cast in the drivers side below the head by the bellhousing. When they went to a 1 piece seal, they all turned to external balance on the flexplate. Before that, only the 400 was external.
thats the fastest way to identify the 2. it'll either say 5.0 or 5.7
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Old March 9th, 2010, 09:09 PM   #8
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Quote:
Originally Posted by jbsjunk View Post
If it's 86 or newer, the displacement is cast in the drivers side below the head by the bellhousing. When they went to a 1 piece seal, they all turned to external balance on the flexplate. Before that, only the 400 was external.
They remained internally balanced. Some may argue that, but its true. There was a counterweight in the crank on the 2 peice seal set ups. When they come out with the 1 peice, there was no room for that counterweight, so they just welded some weight to the flywheel. They are considered internal balance because the harmonic balancer, in this case, is just a dampner unlike on the 400.
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Old March 9th, 2010, 11:07 PM   #9
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So basically just the casting numbers and the 5.0/5.7L on the back of the motor?
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Old March 9th, 2010, 11:10 PM   #10
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Yup, on 86+ engines anyway. A good light and a mirror usually works if it's in the truck.
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Old May 2nd, 2010, 11:57 AM   #11
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casting number or pull a head and measure the bore.. 350 is a 4in bore.. 305 is a 3.73in bore if i rememeboer correctly
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Old May 2nd, 2010, 07:57 PM   #12
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flex plates on 305s are smaller as is the diameter of the balancer. 350's use either a 6" wide flange or an 8" narrow balancer. the 305 ones are about 5" and wide. some even have a step on the ring.
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Old May 2nd, 2010, 09:03 PM   #13
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Quote:
Originally Posted by Yetti View Post
flex plates on 305s are smaller as is the diameter of the balancer. 350's use either a 6" wide flange or an 8" narrow balancer. the 305 ones are about 5" and wide. some even have a step on the ring.
one a one piece rear main motor i think the flex plates are the same.. but i could be mistaken..
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