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Author Topic: 396 vs 427 crankshaft  (Read 5458 times)
jdv69z
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« on: June 05, 2008, 01:50:30 PM »

Are the 396 and 427 crankshaft identical? I thought I read ("Chevrolet by the Numbers" by Alan Colvin) where they had different thicknesses of the counterweights to account for the difference in rotating mass?

Jimmy V.
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Jimmy V.
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« Reply #1 on: June 05, 2008, 02:28:12 PM »

Are the 396 and 427 crankshaft identical?

No.

I thought I read ("Chevrolet by the Numbers" by Alan Colvin) where they had different thicknesses of the counterweights to account for the difference in rotating mass?

Correct.  The 427 counterweights are slightly thicker.

Paul

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dd442
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« Reply #2 on: June 06, 2008, 08:26:32 PM »

Not to be contrary but most cranks I have pulled from 396's and 427's have been #6223 steel cranks. the HiPo 7115'S(Crank) also came in 396, 427's and also been found in older 366 Truck Blocks. Your 375 hp 396's came mostly with 7115's so did your 425/430/435 427's. Most all of your lower HP Big Blocks came with the 6223. The 7115 is a Bigger Crank and has be Factory Nitrited(Black Crank) and Crossed drilled. I have used 6223 cranks in Very HiPo Engines and NEVER had a Problem. Plus 7115's are not easy to come by.  Good Luck
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70 SS 396\350, 69jane, 69 442, 70 Mach 1
nuch_ss396
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« Reply #3 on: June 08, 2008, 10:26:31 AM »

Numerous 427's have been found with '6223 crankshafts.  In fact, I believe all the Yenko & Copo cars used '6223 cranks in their '512 blocks as well.
As noted, the '6223 cranks used in those applications were cross-drilled & thfftrided.

The '7115 crank was an L-88 & ZL-1 oddity.  I believe this was due primarily to the reciprocating weight of those huge piston domes.  I have never
heard of a 396 being found this a '7115 crankshaft.

Colvin's book seems to indicate that 427's used a crankshaft with thicker counter-weights, however my findings don't substantiate this position.
The majority of this information ceoms from years of discussions with 427 owners.......

Nuch
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Steve A.
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dd442
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« Reply #4 on: June 09, 2008, 09:42:52 AM »

I thought the same thing about the 7115 but I have found 2 of them in old model 366's out 67-70 Farm Trucks and could not believe it. and Some of your 396/375hp came with 7115's but as said before 6223 was the common and we all know that GM was not consistant with how they did things. I have found that most books are a Great guideline but not always the exact.
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70 SS 396\350, 69jane, 69 442, 70 Mach 1
hihorse
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« Reply #5 on: June 09, 2008, 04:52:49 PM »

FYI,
6223 out of the 366 were different also because the pilot bushing (car) would not fit, you had to machine the outside diameter of the bushing smaller to make it fit if you were running a standard trans.
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