View attachment 5604255 View attachment 5604256 View attachment 5604257 View attachment 5604258 I have a 66 vette 454 block,427 steel crank, so you could say its a 427 or a 454 motor . She would fly down the road, no issues at all. She was burning a little oil so my buddy tore the motor down....replaced valve seals, rings bearings then he found this, the huge crack in the harmonic balancer neck, right at the keyway.... Any ideas on how it happened. Little history on the car, it was raced 1/8,1/4 miler...
Lose bolt, the balancer absorbs a lot of torsional vibration energy. If its not absoluly tight it will hammer the keyway.
When you build a bitsa, easy to get the balance off. FWIW, the 427" is internally balanced and the 454" is externally balanced. Possible the 454" harmonic balancer might have been used on the 427" crank? FWIW, cracked OEM balancers are not uncommon. Often, they've been roughly handled during removal and installation. I always magnaflux the Packard V8 balancers and maybe one in three is cracked. jack vines
Yeah, per Packards comments above. Some of those big "weights" on the front of the crankshaft are "just", Dampers. Single task is to dampen harmonic vibrations. Some are, Balancer/Dampers. Dual task is to dampen harmonic vibrations AND to act as aditional balancing weights on the crank shaft. They should not...be mixed. Mike
looks like a 427 damper, judging by the relative size of the damper and pulleys. 454 damper is about an inch larger diameter, isn't it? might delete the pics of the car, which is off topic for a few reasons... Cause? I'd just say "shit happens" and replace it.
Not one bad or off the wall answer in posts 2/8. Any or more than one of the reasons given could have been the reason for it cracking. I've seen a couple that were cracked that were obviously beat on with a BFH and probably over a key that wasn't quite right for some reason. I'd really be checking the snout on that crank though. If it was one that was acquired for the build of the engine it may have been through a rough and abusive life before you got it.
Another possible cause, Check the press fit before fitting the new damper, crank may be worn undersize. If the balancer doesn't have the correct press fit and is too loose it won't matter how good the key is or how good the bolt s, the key and damper groove will still get hammered. When you see an engine with a balancer that has been run for a while with a cracked keyway, it also typically frets up the crank snout surface unless the issue is caught quickly.
Oh I dunno if it's too far off base is it? At least it ain't 20s and an LS... just my opinion tho, I don't run this joint
I'd be surprised if that engine didn't leak oil like a sieve! A crack like that should have resulted in a very wet bottom side of the engine.
Somebody got very lucky. Excessive RPMs could have triggered that. NHRA mandates SFI approved dampers for that reason. Must live at 10,000 RPM. It could have ended up like this.
I was going to say the same thing about Pontiacs. I had one break in that area and a piece fell down in the pan promptly pulling the timing chain in half going about 70 down the highway...all because it got loose.
Another thing to check is the fit of the balancer on the crank snout. If the snout of the crank has been polished excessively making the fit loose the resulting wobble can cause the crack,if this is the case this will eventually happen to the new balancer too.
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