engine knock

[blkty]

went to the dealership today to pick up some stuff and got talking to a tech about cranks and turning them down. he promised me that if you turn down a crank it would eventually start knocking. thought i would see what your guys thoughts were on this topic. thanks

 

[turbodig]

Re: engine knock

My thoughts are that you should find a different shop.

Millions of cranks have been cut throughout time, and no "knocking".

In fact, virtually every rebuilt motor bought or sold likely has one journal that has been cut down.

 

[blkty]

Re: engine knock

thats what i thought mine is turned and no problems with mine

 

[NecroWolf]

Re: engine knock

did he give his reasoning behind that?

 

[blkty]

Re: engine knock

no he just told me that

 

[Quickstop [UK]]

Re: engine knock

Crock of bs. If it is turned and the bearings are the wrong size after then yes but otherwise, big fat :bs:

 

[NecroWolf]

Re: engine knock

Crock of bs. If it is turned and the bearings are the wrong size after then yes but otherwise, big fat :bs:

maybe that's how he does it

 

[bezerk]

Re: engine knock

Moral of story, it is very difficult to get a crank back from the shop with the 'perfect' journal size. If it isn't right, it will knock, or fail. Period. My experience has been, this 'perfect size' is tough to achieve.

yes, but does the size of a ''new' untouched crank is in the region where you want it to be? i know they aren't always in specs, and even some high performance machine shops i know grinding brand new cranks because they don't like the specs on it.

 

[turbodig]

Re: engine knock

My machinist found a better grinder that could get it right. Engines quit failing. Now I'm happy.

Moral of story, it is very difficult to get a crank back from the shop with the 'perfect' journal size. If it isn't right, it will knock, or fail. Period. My experience has been, this 'perfect size' is tough to achieve.

As you say, this really depends on the machinist. It also depends on the guy putting the motor together- most garage mechanics aren't going to spend the necessary time to make sure the bearing clearances are "right", much less sending the parts back until they are. Or, picking through a few sets of bearings until you get the right setup.

This is why well-built motors are more expensive, and why it's often better to do this work yourself in absence of a guy you really trust.