Engine autopsy

[Fingers]

I'll look for the info.

 

[TrentNell]

Trent, were those just stock delipped pistons? Hard to tell from the pics

Yes stock pistons that were cut .

Ok, thanks for clearing that up. Only the second set of delipped pistons I've seen fail.

To count all that I know of I would need to take my shoe's off :rofl:

Is it me or has every cracked piston I have seen has blown out on the corner of the wristpin pointing to the rear of the block?

That cant be coincidence

Every one I have ever seen was the same place , some worse than others but all the same. thats why I am buying forged pistons I have seen to many stockers fail , although they do last a while at decent hp levels

 

[GeorgiaDieselGTO]

Yes stock pistons that were cut .



To count all that I know of I would need to take my shoe's off :rofl:



Every one I have ever seen was the same place , some worse than others but all the same. thats why I am buying forged pistons I have seen to many stockers fail , although they do last a while at decent hp levels

that is where everyone that i have seen blow out too.

 

[ripmf666]

What's the difference that makes you say this? Just curious.

When you swap out the lbz rods and piston the extra weight from the when you add the heavier lb7 piston and swap to a aftermarket rod it's to far out of balance. The lb7 block your only changing the rod weight that's not off by much.

 

[JoshH]

I thought the LBZ pistons were heavier than LB7s?

 

[ripmf666]

I thought the LBZ pistons were heavier than LB7s?

I think I posted the weight of them before back when we built mine. I was joking while talking to Guy about how much weight they took out of my crank he said it was from the piston and rod swap.

 

[dmaxalliTech]

Wow, guess its more common then I thought. Out of the loop a bit by now being on the boards lately I guess.

 

[GeorgiaDieselGTO]

I think I posted the weight of them before back when we built mine. I was joking while talking to Guy about how much weight they took out of my crank he said it was from the piston and rod swap.

If he took weight out of the crank that means you rotating asssembly weighed less than stock

 

[05chevy]

Does anyone take weight off the rods or do they do it all on the crank

 

[Micheal Tomac]

Ok, thanks for clearing that up. Only the second set of delipped pistons I've seen fail.

I cracked a delipped LB7 too.

 

[juddski88]

Most of these have been stock piston with machine work, how about the mahle aftermarket cast piston that supposedly had more meat around the wrist pin IIRC?

 

[GeorgiaDieselGTO]

Most of these have been stock piston with machine work, how about the mahle aftermarket cast piston that supposedly had more meat around the wrist pin IIRC?

Cant say how much better they are, but when we do cast ones thats what we use

 

[ripmf666]

If he took weight out of the crank that means you rotating asssembly weighed less than stock

Yes found some of the info last night that we posted awhile back but iPhone battary went dead. The crower rods weight alittle less then stock and the lbz piston has more weight then the lb7 along with the wrist pin is also heavier. If you just swap out on a lbz crank your futher out of balance the doing this on a lb7 like Trent did.

 

[mainer]

Yes found some of the info last night that we posted awhile back but iPhone battary went dead. The crower rods weight alittle less then stock and the lbz piston has more weight then the lb7 along with the wrist pin is also heavier. If you just swap out on a lbz crank your futher out of balance the doing this on a lb7 like Trent did.

so the lb7 and lbz cranks are different weights?

basically what your saying is that if you do rods cut pistons on lb7 your not that far out of balance and its seems as though it holds up fairly well. but on an lbz rods and cut lb7/lly pistons would be out of balance by a fair amount.


now another question whats the weight difference between lb7 and lbz rods??

 

[scratchrob13]

Just balance the rotating assembly. Done.

 

[dmaxalliTech]

Just balance the rotating assembly. Done.

My thoughts exactly

 

[HEEPJEEP]

so the lb7 and lbz cranks are different weights?

basically what your saying is that if you do rods cut pistons on lb7 your not that far out of balance and its seems as though it holds up fairly well. but on an lbz rods and cut lb7/lly pistons would be out of balance by a fair amount.


now another question whats the weight difference between lb7 and lbz rods??

Just balance the rotating assembly. Done.

Yep, needs to be balanced. :thumb:

 

[TrentNell]

Just balance the rotating assembly. Done.

My thoughts exactly

Yep, needs to be balanced. :thumb:

I guess i would have picked up several 10ths if i wouldn't have skipped that step , daaaaaaaang :rofl:

JK guys I agree its best but i see no real penalty from skipping it on my build. and for what the motor was built for . If it was being built for DD / 10's of thousands of miles , then yes , and if the crank would have been pulled it would have went out for a balance , but the crank never left the block.

 

[TheBac]

Balance the motor. Its just a good thing to do. The shop that did mine had to use every weight they owned to get the crank right.

 

[mainer]

Yep, needs to be balanced. :thumb:

was yours balanced???