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The easy way to tell is to get the block casting numbers on the back driver's side right behind the head and check the id numbers online.. that's at least how I did it.. also on my 350 it says gm 5.7 and on a 305 I've seen gm 5.0
 

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Ditto, casting number is your friend. Heads can be swapped, cranks and everything else. But that casting number will identify if it's a 4" bore or not. It will at least eliminate the possibility of a 265, 267, 283, 305, 307 and the 400 blocks.
 
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marv...............it apperars if I read the no currect threw the grease I have a 350 gmpp heads 286-300 ona a 305 block, The downfalls or problems with this setup?and what do I really have? Thanks:beer:
 

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check the stamping on the block,front top right side of the block will tell ya what kind of engine you might have.the reason I said "Might" is because it might have been decked..:poke::beer:
 

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If the motor is in one piece, look at the dampner. 305 and 396 will have smaller dampners then 350 and 454. If they are apart, check the bores. Best of my memory, 305 has the same bore as a 283. And, the stroke of a 350. The 396 is all by its self. smaller bore and stroke than 454.

396 has the same stroke as a 427. 427 has the same bore as a 454. Plus all 454 were flywheel (flexplate) balanced. And, had cut-outs in the pan rail to clear the rods. Just a FYI. :nanawrench:
Oh, and most blocks after '87 and all crate motors should have a litter stamping on them.

Hope that helps.

 

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For the 396-454 engines (early)they have a machined pad on the passenger side front of the block with a code punched into it,on later blocks I believe you have to follow the casting # .
The other question you have as I take it is you have a 305 block with 350 heads is that right?
 

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With the GMPP heads it appears you have a motor that has been remanufacturered with ??????? and who knows what parts are really there.
What casting #'s did you find?

Like goodcruiser said, the same holds true with all GM engines. On the front of there block, passengers side, down at the base of the head there is a pad with #'s. Get all of the numbers and we can decode it for you. Usually you have to remove the alternator (or A/C depending on year and equipment) to see them. May or may not be configured as it was originally, but...... If you found it's a 305 block,, it's a 305 and not really any options.

74chick, close but no cigar on that one. The 305 has a one off bore of 3.736" unique to the 305. The 283 was 3.875" bore
 

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Discussion Starter · #10 ·
So the answer is (no) there is no quick or easy way to observe the difference between the two.
Not like (if it's a 305 the dip stick will drivers side and if it's a 350 then it would be on the other?)
So how many people would you think buys cars that they think have one or the other to find out later their wrong?:dontknow:
Donny
 

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alot of people do.. see it on craigslist all the time they say they have a ss el camino with a 350 and if u dont know any thing about the ss or caminos then u believe what u read.... thats why always check the casting numbers... had a guy tryin to sell me a 305 and he was sayin and swearing it was a 350 ran the numbers proved him wrong lol:poke:
 

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This will be the last in the series of?, numbers under alternator have been punched out, not decked clean so there just unreadable , 5.0 is stamped next to trans, when I looked up the no on the heads it was 1987 ,specific and the valve cover bolts are in the center.one other thing ,a lot of the wires that are not connected are burnt or melted, was gonna post some pictures if I ever get a chance Thanks all
 

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If the motor is in one piece, look at the dampner. 305 and 396 will have smaller dampners then 350 and 454.


396 has the same stroke as a 427. 427 has the same bore as a 454. Plus all 454 were flywheel (flexplate) balanced. And, had cut-outs in the pan rail to clear the rods. Just a FYI. :nanawrench:

Hope that helps.

Not all 305 engines had a small balancer---many had an 8" balancer,
All 454 did not have reliefs for the tie rods---full size passenger car, trucks, and I think the vette did not need them-----the A-Body cars needed the reliefs.
 

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Harmonic balancer size is different
 
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