Spun Front Main Bearing 454 Mkiv Repairable?

1980RS

Powder metal LT1 rods eh? Do you have ARP rod bolts in those or stock rod bolts? Not realted to your failure just I am interested to see someone using the PM rods at a college ability level than me (I am using them)
Steve

I am using PM rods and they are suppost to be able to withstand 500hp according to GM.

Equally for breaking cranks I broke two one twelvemonth, 396 forged steel and a 327 forged steel GM ones. Best thing to do is when you get a new one have it magnifluxed. A good friend of mine bought a new LS7 [454] and took it apart to accept it blueprinted and found the crank had a hair line crack roght from the factory. Become them checked as it will salve you lot from a lot of problems after.

I have used bandage GM cranks for years and take never had any problems and some of the new cheap stuff scares me.

z28rod

my buddy has a comp elim. car. runs a 305 cu in. motor, no not a usuall 305 , but its a 4" bore bored out and 283 small journal steel gm cranks, he spins 11 grand every pass and has never broken a crank.......... and so who knows... i bet that motor wasnt counterbalanced proberly or incorrect balancer or both, that chief heated upwards and that crank failed...... ????

tomsti

It's hard to see from the picture but the front end master cap appears to be a little squished looking around the bearing area. Non sure if thats sealer or something, did the mains spec out ok during the build, do they still? Besides if this is a 383 shouldn't there be some reliefs on the side by the oil pan expanse for the rods to articulate? Perhaps the picture doesn't prove them.

ProStreet383

What practice y'all wait from a Chinese made part? My friends 406 just chucked a scat rod that just had 200 miles and twenty passes down the track on them. I am sorry it happened to you. Information technology was about probable a hair line crevice that was overlooked and information technology finally let go.

chevy-stu

Thanks for some great replies fellas, definately some food for thought in that location.

To respond some questions:

What damper did you have?

I see no testify that the connecting rod big ends in view are focused, was the rotating associates counterbalanced? That would be my first question. Second would be what harmonic was used. (esp if the answer to question i is no) I've witnessed iii 9000 series Scat cranks fail, ii of them were like the i in the moving picture. All 3 failed were in dirt oval track applications. Scat's response was they are good for 500 HP, but we quit using cast cranks in dirt oval applications, and quit seeing broken cranks as a result.

The original 6.half dozen" cast atomic number 26 balancer supplied with the engine had a mistake and the outer section had moved, and then was replaced with a improve Pro Race steel one of the same size. There were some bug with no timing tab beingness fitted so interesting that the balancer and timing points were raised..

The assembly was supposedly balanced before so should have been no issues with that. It ran nicely too with no vibration so all seemed good..

Every time I have heard/seen a bandage creepo break it was in an oval track application.

The car is used for a footling route racing and does get some sustained revs compared to a strip car, and so I guess it'south similar use to Oval.

Powder metal LT1 rods eh? Do y'all accept ARP rod bolts in those or stock rod bolts? Non realted to your failure but I am interested to see someone using the PM rods at a higher ability level than me (I am using them)
Steve

These are alledgedly ZZ4 rods, so is that the same spec as LT1 ? It's unlikely the rods are an problem.

my buddy has a comp elim. auto. runs a 305 cu in. motor, no not a usuall 305 , merely its a 4" diameter bored out and 283 small journal steel gm cranks, he spins eleven m every pass and has never cleaved a crank.......... so who knows... i bet that motor wasnt balanced proberly or wrong balancer or both, that main heated up and that crank failed...... ????

Every bit said already information technology has 'alledgedly' been balanced, but the balancer was replaced. I promise information technology isn't this every bit information technology's supposed to be a better balancer..

Another guy that's seen the damage, spotted the weights on the front, and said the crank would have had to be drilled and had these pressed in, and suggested mayhap some stress damaged occurred during this procedure.. ?

I am having the engine rebuilt, but I'chiliad seriously out of pocket, every bit the whole crate engine was shipped from NY to me here in London, and then it'due south not as if I can go knocking on the door of who I bought it from.
Is information technology worth chasing Scat ??

deputyrob

i'm focusing on the bearing saddle for the offset chief journal. the metal is cone shaped merely to the centre of the bearing saddle and the metallic is pushed downward in the front. to me this says that the crank snout may have been aptitude..or you had a actually messed up balancer.

badazz81z28

You lot never know....maybe y'all got a bad lot?

Bikefixr

I think your block is toast. Expect at the master saddle. There is a definite harm line simply forrad of the oil feed hole. The crank was bent a little (not from the mallory metal install in the counterwight, that is the right way to exercise information technology as shown in your pic). The front end of the crank was wobnling around and wiped out the front half of the bearing, it probabally spun and took the metal in the block with it. Expect at the mating surface of the cake right at the bolt hole. Information technology gets wider towards the front of the block. Block is wasted..non plenty spare metal there to machine that clean.

chevy-stu

I think your block is toast. Look at the principal saddle. There is a definite harm line just forrad of the oil feed pigsty. The crank was bent a little (not from the mallory metal install in the counterwight, that is the correct way to do it as shown in your flick). The front of the crank was wobnling effectually and wiped out the front half of the begetting, it probabally spun and took the metal in the cake with it. Look at the mating surface of the block right at the commodities pigsty. It gets wider towards the front of the cake. Cake is wasted..not enough spare metal there to machine that clean.

Yes, the cake has had it. Information technology was turning for a minute or and so with that break so it spun itself all over the place in the main saddle (yous should see the state of begetting !!!!)
I was looking into getting some metal added and getting it machined downward, merely as the pistons and rods are probably gonna exist replaced now, at that place'south no existent signal pursuing working on this block. Sourced another one though luckily.

pdq67

Look, my quondam junk301 west/ a '55, 265 crank, who know'south what wider beamed 283 rods, Westward/JCW el-cheapo 1/8" over domed 283 cast pistons UNBALANCED would get seven,500 rpm in a NYM FINE!!

FORGED creepo tho.........

pdq67