496 BB with internal balance

legerwn

Active Member
When I had this engine put together the builder internally balanced it, at the time it wasn't a big deal.

I have managed to break some teeth off the flex-plate and now need to replace it.

I tried looking up a internally balanced flex-plate for a BBC gut come up with nothing. I see they offer the BB balance weight that is added on to the crank so they must offer a flex-plate that does not have the weight welded to it.

Anyone have an idea of what flex-plate I can use?

I guess I can get the 454 flex-plate and grind the weight off.

I do have plans to pull the engine in the future to have it stroked to a 540 but am not ready to do this right now.

I'm going to pull the broke flex-plate to see if I can see any balancing marks on it to make sure I don't have the have the new flex-plate balanced before the install.

thanks for any help, Neal
 
http://www.ebay.com/itm/Scat-SFI-Small- ... 1129052466

http://www.ebay.com/itm/Scat-SFI-Small- ... 32&vxp=mtr

the 427 and 396 BIG BLOCK ENGINES WERE INTERNALLY BALLANCED SO IF YOU HAVE THE EARLY 2 PEICE REAR SEAL BLOCK AND CRANK THOSE SHOULD BOLT ON,
ID ALSO POINT OUT THE OTHER OPTION, you should think about

if your replacing a ring gear, on a flex plate or flywheel, this is the route ID take, as its sure to keep the balance correct and any decent machine shop can replace a flex plate ring gear, but be aware fly wheel ring gears are generally heated and clamp on the flywheel as they shrink as they cool, flex plate will generally require careful TIG or MIG welding to hold them in place as flex plates are far thinner and more flexible

http://www.crossmembers.com/shop/fly-wheels-c-18.html

http://www.summitracing.com/popup/calcsandtools/stroker-combinations
sold as a separate replacement part

http://www.summitracing.com/parts/atp-za500
atp-za500_vk_xl.jpg


viewtopic.php?f=53&t=5155&p=14949#p14949

Engine Balance: Internal vs. External
An engine must be balanced to ensure smooth operation. It minimizes vibration and maximizes engine life. Balancing can be internal, external, or a combination of both.

Balancing an engine means offsetting the weight of the pistons and rods. This involves adding or removing weight from the crankshaft. The Harmonic Balancer and/or the flexplate or flywheel can also be weighted.

Internal Balance
An internally balanced engine has all the counterweight on the crank. External parts like the balancer and flexplate/flywheel have a neutral balance. They will not affect the other rotating parts.

External Balance
If the crank's counterweights are too light, the engine must be externally balanced. This involves adding weight to the harmonic balancer and/or the flexplate or flywheel.

How does it affect performance?
Generally speaking, internal balance is the better option. External counterweights can cause the crankshaft to flex at high rpm. This can cause engine damage. However, either type of balance is fine for most engines.

Converting from external to internal balance can be expensive. It requires a new crankshaft, harmonic balancer, and/or flywheel or flexplate. You may also need to clearance the block for the larger counterweights. Unless you're racing, it's easiest to balance the engine the same way the factory did.

Engine Type Factory Balance Method
Chevy 305/350 (2-piece rear main seal) Internal
Chevy 396-427 Big Blocks
Chevy LS Engines
Ford Modular Engines
Chevy 400/454 External
Ford 302/351W
Chevy 350 (1-piece rear main seal, including LT1) Combination of Internal & External


Notes
Balanced Rotating Assemblies come pre-balanced from the manufacturer. These can be installed without taking the parts to the machine shop.

If you buy an Unbalanced Rotating Kit, you will need to have it balanced before it's installed. The same is true if you buy a crankshaft, connecting rods, and pistons separately.

Crankshafts are listed as internal or external balance. This doesn't mean it's already balanced. It just tells you how it's intended to be balanced. It must be checked with the specific piston and rod combination you use.
 
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If you need an SFI tagged flex plate, just call B&M and ask for a 164 tooth internally balanced flex plat. Any BBC Flex Plat without a weight will work.
 
Thanks for the info,

I still have to pull it and see if its broke anywhere other than the teeth to know if I can just replace the outer ring.

It will more than likely be quicker if I just order another one or see if one of the local parts houses have one in stock.

Neal
 
While I was making a degree wheel for my distributor I found the culprit for the broken flex-plate, the rotor had came loose, screws backed off and it was loose in the cap.

I replaced the rotor/cap around 8 or so months back,

when I replaced the cap and rotor it didn't come with the little star lock washers it came with bevel washers (MSD billet).

I will lock-tight them in from now on.

Neal :x
 
yes, it took me and most of us years , but eventually youll realize the importance of doing all the little seemingly trivial steps like use of loc-tite and anti-seize on threads where its applicable, during the assembly or maintenance process,you learn to carefully test and inspect problems and not to assume you know whats wrong without testing.and you learn to take the time to read, checking the shop manual for assembly instructions, rather than assuming you know exactly what your doing, and that the quality of the components used is frequently more important than the price paid within reasonable limits, of course. but you'll rarely if ever save money in the long run using the least expensive components.
I can,t count the times I,ve seen what appeared to be huge mechanical failures , come down to either lack of proper assembly or lack of proper maintenance.
I well remember purchasing a 375 hp 396 BBC from a friend who swore it "THREW A ROD OR SPUN A BEARING" so I bought a replacement 454 cubic inch, 450 hp engine! An engine that I bought from him as he thought it was nearly worthless and taking up floor space in his garage, an engine that I took home hoping to salvage a few parts, after I bought it for peanuts, and put it on an engine stand, and did a total disassembly, and inspection, turned out to have a busted rocker and two broken valve springs
 
when I was playing with my timing When I was changing springs and bushings. I found the same loose screws on my rotor glad I caught it before anything bad happened
 
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