motor knocking sound at start up?

[djwarner]

Everyone has focused on the lifters. I have the same problem with a L24. These are overhead cam engines without lifters. Initially, I thought I had a rod knock until I took it to the local long-time Z guru. He noted that if it doesn't get worse on acceleration, it isn't rod knock. He quickly pointed out that it is the timing chain tensioner. The tensioner is held in place with a spring and adds oil pressure to keep the slop to a minimum. As the tensioner wears and its spring tires, slop allows the chain to rattle until oil pressure builds.

 

I noted the price of a chain tensioner, gaskets and oil seal are minimal and he noted that the labor is not. Suggested I let it go until overhaul. Said he'd seen engines go over 250K with the problem and no consequences. Since then I've put another 6K on my 175K engine, with no noticeable affect.

[Heroez]

Thats an interesting experience. Im just going to ignore it for now. I have another turbo motor on an engine stand. Had been in a barn for years. I may just put some time into it, cleaning it up, replace the timing chain/tensioner, gaskets. Maybe even some nice tough pistons. That way Im ready to go when something gives on this motor. It never ends man. Some days I want to sell the classic Z cars and all the crap I accumulated that goes with them, buy a used 370 and retire from this.

Edited March 25, 2013 by Heroez

[nismosilvia]

Yaa I think your over analysing the motor. It's almost 30yrs old it's not comparable too quite modern engines. They all have some sort of ticking going on it sounds like your doing good maintenance that's all you can really do

[Xnke]

Yeah....These motors DO have "lifters" but only the 1983 turbo models got the hydraulic lifter assemblies that DO act like hydraulic lifters and DO go bad. Replacements are not available.

 

Yes, timing chain slap is another problem these engines get when they get old...the two noises are distinct and seperable.