My 95Z is about to roll 200,000kms(125,000miles) and I'm getting concerned about the stock timing chain in there. The car sees daily driver status with the occasional auto-cross(1/month).

When should these chains be replaced? The car still runs perfect

 

with 125k, its always a chance. Some can last a long time(200k+), and others last not. The main time ive seen any fail is due to a shock or jurk taken in on the engine adding extra load on it causing it to break right then. You do not want that to happen at all. It can mess up all kinds of stuff. I say if you have some extra money sitting around, replace it. If not, dont worry to much about it.

 

btw, how do you like the rx headers? Im about to get some. How big of a diff did you feel? Did you loose much low-end in return for top-end?

 

My oem chain was loose after 45k miles and was removed during a cam/lifter change. I didn't notice any problems with timing though before I removed it and replaced it with the GMPPs LT1/LT4 HD timing set. There is no comparision between the oem and the HD set.

I would believe that with 125k miles, you have some slop in the chain.

 

Zedzag,

Good question, I was wondering the same thing.


Don 97 SS,

Can you tell us the difference between the HD vs OEM??
ALso, how much??

THANKS~~

 

my motor had about 80 on it and when i took of the timing cover and spun the motor over by hand, the timing chain would catch and snag on the crank gear due to the slop in it...put a new chian and its like butter..

 

I'll probably slowly start collecting parts for a cam swap then because it's only one step further once it's all apart.

Jason- I may have lost a touch of bottom end but my midrange and top end are much better. The car revs quicker and pulls hard past 5500 rpm where before it would start to level off. My old dyno graph shows the power peaked at ~ 5400 with the manifolds and now it probably moved up to ~5700. It also sounds better too.

 

My stock timing chain had a ton of slack in it with only about 45k on the motor.

 

how much would a new chain be roughly?
i'm doing a full tune-up/replacing all fluids thing to my Z and might as well do this while i'm at it
also, would it be that advantageous to upgrade to the lt1/lt4 hd timing set?

 

I am doing this from memory. Basically, the ED or HD is as its name implies, a HD more durable design chain and gears. The oem is a multilink bar chain, the HD is a roller type. I believe the gears are hardened and appear a little meatier than the thinner and lighter appearing oem. Also, the ED is not a "race only" part as I first thought. It does not make any noise or and works fine on a daily driver car (like mine). There might be more technical info in the GMPP catalog. Some vendors like Pace or Scoggins and Dickey have it on line. One you see them next to each other, there is no way one would pick the oem chain. The price of the ED set is the only drawback.

 

my brand new clevite oem chain was 30 bucks...the cloyes was 32.

 

i broke mine exactly at 150,000! I bent a couple of valves. I was turning it really hard, and it shifted and just broke.

 

i replaced mine at 102k, and it was pretty loose.