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Dead LT1


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Well last night the car felt like it was missing. I had just gotten gas and I thought maybe I had gotten bad gas, so I hammered it and at that point I knew it was a little more than a simple missing. The motor was vibrating real bad. The motor quit right away and smoke came out everywhere... hmm that's not usually a good thing. I pulled over, oil and antifreeze was pouring out (I don't mean dripping). Popped the hood and the balancer was about at a 30 degree angle.

 

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I pulled one of the valve covers and everything looked good. I'll pull the pan tonight and take a better look and see what really happened, but from the pics it looks like the block broke above at least the front main and began the destruction. The timing chain stayed in tact and I am hoping that means the valves were spared. Hopefully just a short block is all I'll need to get back.

 

Jody

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I'll second that, any idea what let go to cause that? the balancer start to spin off?

I always worry abit about no key and keyway......

 

I was also interested in your build on the motor, I was going to PM you after I tear down my other LT1 and start to rebuild it.

WOW serious damage!

 

Greg

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Well I pulled the oil pan and took a few more pictures.

The crank is in 2 pieces. Broken right in front of the second main bearing. I don't know if the block broke first and took out the crank or if the crank broke and took out the block... it doesn't matter I guess, it's trash. The first 2 rods are bent and the block is beat up pretty good. This motor was built MANY years ago and it has seen quite a bit of abuse. The balancer hub on this one was keyed and it was not coming off.

I also pulled the rockers on one side and all of the push rods are perfect, so I am still hoping the heads/valves survived.

 

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Jody

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Lunati Pro Mod 6" rods and Lunati Forged Crank. This wasn't the cheap one.

The third picture down is showing where the crank broke, that round hole was/is the oil hole that was in the middle of the crank. The 4th pic is the broken part jammed on the counterweight. The 5th picture shows the bent rod after the crank broke and it was still spinning.

The last pic shows the remains of the part of the block where the front crank/bearing main used to bolt into.

I'll probably never know for sure what failed first, but one thing goes and... well you see.

I am not looking for answers, just pictures of destruction is usually fun to look at..... more entertaining when it is not yours though :-)

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Wow, thats pretty crazy...I have had a 406 in my stock suspenion vega for the last couple years with a Lunati crank and rods....Same stuff your using there. And i have sprayed it to a 6.50 at 109 in the 1/8 and now I know for sure im going to get it all magged and checked before it goes back together. How high do you normally spin it?

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its very unlikely to be a defective set of rods , a bad damper or a badly machined crank thats at fault, carefull examination of the components will usually indicate the source but without careful examination of the stress fracture , and all components in the engine it will be hard to verify the source,

stress is cumulative having the engine ballanced and correctly clearanced is mandatory.

maintaining proper lubrication and valve train control is mandatory.

I see guys blame the crank and rods for failures that were really valve train or detonation related, no piston, rod or crank will successfuly compress a bent valve or a busted chunk of piston ring land that broke loose due to lack of valve control or detonation damage, but dampers do go out of index, and cranks do occasionally have stress risers, bearings do occasionally get starved for oil, timing gets moved, detonation can result, etc.

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I spin that motor to 7K often. That is/was the fun part of driving this around.

I'll take pictures of the pistons/valves when I get it apart. Who knows there may be an issue there, but I am hoping there has been no destruction on the top end. That motor came from my '96 Z28 that I bought new and put a ton of mileage on and it wasn't babied either. The motor has been pulled apart a number of times and the Trick Flow heads were gone through two years ago when I put them on. If anything looks out of line it has been replaced, but I can say I don't go through it often. I haven't been inside the motor since I did the heads and cam 2 years ago. And if this didn't happen I probably wouldn't have been planning on going back in it either.

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I pulled the driver side head and took a few pictures. I'll try and get the passenger side off later this week. The valves took some abuse and bent. I obviously will take them to get the valves replaced and checked out and hope the seats and guides are OK (you always have to hope). Amazing that the push rods are still straight.

Pretty minor as to what could have happened. Once I got the timing chain cover off, the 2 sections of the crank were able to be turned separately fairly easily, It could have looked much worse in here.

 

 

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jbc3: Whose and what type lifters did you use to spin it to 7000 RPM? Either the crank had a defect in it or the damper induced the crank to fail. Whose and what type of damper were you using on this engine. I am building a SBC similar to this and want to gain knowledge from your unfortunate experience. What was the displacement of the engine?
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  • 2 weeks later...
Comp Cam Pro Mag 1.6RR

 

rockers.JPG

 

It was a 385 stroker.

I don't remember the name of the damper, but it is one that I got through my machine shop and it was one that bolted to the billet hub.

jbc3: Which lifters did you use in this engine? Please advise. Thanks.

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The lifters I used are the Comp R lifters, I think they are 875-16.

 

Head update:

I took the heads to my machine shop and after looking at them and pulling a couple of the obvious valves my guy said the damage to the heads is nothing at worst. We are replacing the valves and seals and skimming the heads, but the seats all look good. Obviously if once he gets them completely apart and he finds any other issues he'll address them...

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I liked your line how seeing damage is better when it is not your engine. That is a fact, but we all have blow up motors...

 

I must say your damage appears to be extreme. Heres to you getting it back together and out running the last setup.

 

Good luck

Jack

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