396/402bbc- internal/external balance ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bigblok · 08-30-2002, 12:26 PM

My beautiful machine is out again- rod bearing on #5keeps going.
Rebuilder replaced crank, bearings, rods twice. He said this motor is internally balanced, but others have told me it could be either, and others still have told me all bigblocks were external. rebuilder has no explanation for bearing wipeout. ANY INFO GREATLY APPRECIATED. I want my truck back!

tom hand · 08-30-2002, 12:32 PM

I thought that 396/427 were internal and 454/502 were external

Longhorn Man · 08-30-2002, 01:09 PM

While i don' know about the 502, I have been told that the 454 is the only externial ballanced big block.
Might be time to find a new engine guy.

kxmotox247 · 08-30-2002, 01:28 PM

Something is funny here...
Maybe the engine builder should be calibrating his equipment. Could it be a bent journal? How about debris in the oil passage blocking flow and starving it of oil?
That has to be frustrating.
I could be wrong but I thought 454's were the only externally balanced.

67 SS · 08-30-2002, 07:22 PM

The smallblock 400 & big block 454 are externally balanced.Not sure about the 502.The crank should interchange between the 396,402,427and I think the 366.Has the block been linebored?(I think thats what they call it)Has the crank been checked for straightness?

Chevyman69 · 08-30-2002, 09:09 PM

The only externally balanced BB I know of of is the 454( I think the 502 might be as well, but I don't know). Sounds like a good engine guy to run away from. All the cranks will interchange(366,396,427) and even a 454's can be installed if the block is clearanced and you run the external balanced accessories. Sounds like an incorrectly measured journal or a bad crank, but at any rate find a engine guy that knows something.

Ratpowerd67 · 08-30-2002, 10:52 PM

the 454 is the only external motor. i should know, i have one in my 67.......rat

mikep · 08-30-2002, 11:50 PM

400 is

454 is

502 is

everything else isnt

08-30-2002, 12:26 PM	#1
bigblok Registered User Join Date: May 2001 Location: bangor,pa usa Posts: 29	396/402bbc- internal/external balance ? My beautiful machine is out again- rod bearing on #5keeps going. Rebuilder replaced crank, bearings, rods twice. He said this motor is internally balanced, but others have told me it could be either, and others still have told me all bigblocks were external. rebuilder has no explanation for bearing wipeout. ANY INFO GREATLY APPRECIATED. I want my truck back! __________________ 72 C10 475HP 402BBC Yes, it's fun, but gas ain't cheap!

08-30-2002, 12:32 PM	#2
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	I thought that 396/427 were internal and 454/502 were external __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

08-30-2002, 01:28 PM	#4
kxmotox247 Senior Member Join Date: Jul 2002 Location: Champaign, IL Posts: 1,397	Something is funny here... Maybe the engine builder should be calibrating his equipment. Could it be a bent journal? How about debris in the oil passage blocking flow and starving it of oil? That has to be frustrating. I could be wrong but I thought 454's were the only externally balanced. __________________ Baby Blue's Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=652776 Project 68's Build Thread: http://67-72chevytrucks.com/vboard/s...17#post8442117 www.stonecolumnclassics.com Email: Josh@stonecolumnclassics.com

08-30-2002, 09:09 PM	#6
Chevyman69 Vortec 350's Suck Join Date: Nov 2000 Location: Pickardville Alberta Canada Posts: 544	The only externally balanced BB I know of of is the 454( I think the 502 might be as well, but I don't know). Sounds like a good engine guy to run away from. All the cranks will interchange(366,396,427) and even a 454's can be installed if the block is clearanced and you run the external balanced accessories. Sounds like an incorrectly measured journal or a bad crank, but at any rate find a engine guy that knows something. __________________ 69 Chev CST 10 reg cab lwb Daily Driver: 92 Chev Reg Cab LWB Silverado 4x4, K.I.A 7:51 AM 04/22/03 Will be resurrected

08-30-2002, 11:50 PM	#8
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	400 is 454 is 502 is everything else isnt __________________ No truck :-(

08-30-2002, 01:09 PM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	While i don' know about the 502, I have been told that the 454 is the only externial ballanced big block. Might be time to find a new engine guy.

08-30-2002, 07:22 PM	#5
67 SS Registered User Join Date: Jun 2002 Location: NW ARKANSAS Posts: 258	The smallblock 400 & big block 454 are externally balanced.Not sure about the 502.The crank should interchange between the 396,402,427and I think the 366.Has the block been linebored?(I think thats what they call it)Has the crank been checked for straightness?

08-30-2002, 10:52 PM	#7
Ratpowerd67 Registered User Join Date: Aug 2002 Location: Trenton ,Texas Posts: 328	the 454 is the only external motor. i should know, i have one in my 67.......rat

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