Big end

[VZSS]

Hi, I tried google with no luck, I have a L76 with a possible failed lifter, the quotes I get back say if the big end has spun it will need a full rebuild, so the question is, what is a big end and how would it spin? Must be a destructive thing lol, pictures would be good if anyone has any, thanks

 

[Tonner Matt]

# Please note that this is only a very brief description.

A Big End is the large end of the conrod that attaches to the crankshaft.
A big end will also be in reference to the Big End bearing on that conrod.
When your mechanic says it may have spun a big end, he is referring to the Conrod Big End bearing possibly moving (Having Spun) from it's installed position in the conrod big end. Hence the term "Spun a big end"
There are multiple reasons as to why a Big End would spin, if it has though, at a minimum you would need to have some machining work done to correct any damage that has been caused.
# If it has spun a big end as suggested, the only way to properly diagnose it would be to dismantle the engine and inspect the damage.
# I would talk to the guys at your local performance shop and see what they have to say about it.

 

[VZSS]

Thanks for the info its appreciated, would a failed lifter cause a big end to go? Or are they trying to say the lifter might be ok but the knocking noise could just be the big end?

By the sounds of this I would be better off doing both the cam lifters etc and bottom end rebuild so 20'000 kms down the track I won't be scared to drive it, seems to be a common thing

 

[Reaper]

Had a failed lifter in a LS3. Sadly I can confirm that a lifter has the possibility to take a big end, piston and camshaft with it.

 

[VZSS]

Ahh thanks I get it now, that helps. Now I know what I am in for, thanks again guys

 

[Tonner Matt]

A failed lifter would definitely damage the cam and the big end bearing and more, especially if the needle roller bearings from the lifter start making their way through the engine.
Possibly they are saying lifters are O.K and big end is causing the knocking noise. Hard to verify without hearing the noise in person.
Most big end issues I have encountered over the years have been very distinct in their sound, a very deep thumping knock.
If it is the worst case scenario and you are up for a rebuild, it would be the perfect time to fit a cam and upgrade the valvetrain. Especially considering the engine will be out of the car being repaired anyway and it will be cheaper than doing it later on down the track after the engine has been refitted to the car

 

[VZSS]

A failed lifter would damage the cam not the big end bearing, but anything is possible.
Possibly they are saying lifters are O.K and big end is causing the knocking noise. Hard to verify without hearing the noise in person.
Most big end issues I have encountered over the years have been very distinct in their sound, a very deep thumping knock.
If it is the worst case scenario and you are up for a rebuild, it would be the perfect time to fit a cam and upgrade the valvetrain. Especially considering the engine will be out of the car being repaired anyway and it will be cheaper than doing it later on down the track after the engine has been refitted to the car

Here is a vid, what do you think?

https://www.youtube.com/watch?v=uHNIhvsQhtA

 

[Tonner Matt]

It is possible that is a big end knock, but I cannot say 100% that it is. The only problem I find with videos is that they don't really replicate the sound properly.
Unfortunately it is time to find a good mechanic or engine rebuild shop as that motor is going to have to come apart to some degree either way to be diagnosed and repaired.
Try to avoid starting it and definitely don't be driving it while it's knocking like that though.

 

[VZSS]

thanks mate yer it has not been started since the vid, will have to get it trucked to Perth

 

[kiwicon]

i can hear wind .. give it a small bit of juice, if it sounds like a tractor... then yip big end.. as said above a failed lifter "shouldn't" spin a bearing...

Fix.
Either a new/2nd hand crank (measured if 2nd hand) and new rings..
Or use current crank and get different size ring for where it spun on the crank.. Not really recommended thou..

never done a commodore, but on the japper I did, twas a motor out job.