Can the LT5 experts fill me in on.....

[Roadster]

Ok, I think I have an idea why, but am not really sure, so can the LT5 experts who have the knowledge and understanding of this engine explain the following to me....
Why is it that if you let the Z sit for a week or even two weeks before you start the engine, that there is not any chain rattle upon first start-up???
I understand why there is chain rattle during some restarts, and that there is a kit available (which I have) that once installed, eliminates that problem or almost completely eliminates the problem.

We had the Z out today, and first start-up, no noise, most restarts after that the dreaded chain rattle.....
Just trying to learn more about the system......thanks for any info........

[We Gone]

No expert here but it sounds like you have a good check valve in your oil filter.

I have no chain rattle on my 91 or 93 even if they set many weeks. Both have Blue GM filters.

[Roadster]

No expert here but it sounds like you have a good check valve in your oil filter.

I have no chain rattle on my 91 or 93 even if they set many weeks. Both have Blue GM filters.

That would seem to be true, but its on the restarts that it appears the check valve isn't working as it should, only that it appears to work better when the engine is cold as opposed to when the engine has been running and is hot!!!???
I also have a Blue GM filter. Hopefully over the winter I will attempt to install the kit for this, just have to see what the time factor allows me to do....as there is always something going on........:)

[Jim Nolan]

Mine went away years ago after my second synthetic oil change. I use the blue PF970.

[Kevin]

chain rattle is annoying but not harmful. I don't even notice it anymore

[Karl]

I barely notice it and that is only if the car sits for a long time. Also the car starts quicker (or at least seems to) if I turn on the ignition first wait about 3 seconds then start.

[Roadster]

I barely notice it and that is only if the car sits for a long time. Also the car starts quicker (or at least seems to) if I turn on the ignition first wait about 3 seconds then start.

chain rattle is annoying but not harmful. I don't even notice it anymore

I hear you on that. ...if mine sits for day or longer no rattle on startup. ...as mentioned earlier, its just those hot or warm restarts that bug me.....I am using Mobil 1 , might switch to Amsoil next time around and hopefully get that kit installed

[spork2367]

I've been using the white "Napa Gold" filters that are made by Wix and they have a great anti drain back valve. Zero rattle.

[secondchance]

I hear you on that. ...if mine sits for day or longer no rattle on startup. ...as mentioned earlier, its just those hot or warm restarts that bug me.....I am using Mobil , might switch to Amsoil next time around and hopefully get that kit

I am not a mechanical engineer so my guess may be wrong. Having said that, from what you are saying, it seems, when oil is fully warmed up and engine start is initiated oil draining out of hydraulic tensioner is faster then the oil system pressure build up to feed the tensioner. Whereas, when the oil is cold (perhaps due to higher viscosity) oil is being held in the hydraulic tensioner longer and pressure build up is seemless.
I noticed that if I turn the key without starting 2-3 times (did it to intentionally to move the pulleys a bit) when I actually start chain rattle was severe which never happens on daily normal start. I concluded that when I ran the motor w/o starting oil in the tensiners were being drained and w/o actually running were not replenished w/ system pressure. Just my theory.

[Roadster]

I've been using the white "Napa Gold" filters that are made by Wix and they have a great anti drain back valve. Zero rattle.

I also have a Mobil 1 filter, along with the Bosch oil filter to use in the future, but just might try the Napa Gold, like you have....


I am not a mechanical engineer so my guess may be wrong. Having said that, from what you are saying, it seems, when oil is fully warmed up and engine start is initiated oil draining out of hydraulic tensioner is faster then the oil system pressure build up to feed the tensioner. Whereas, when the oil is cold (perhaps due to higher viscosity) oil is being held in the hydraulic tensioner longer and pressure build up is seemless.
I noticed that if I turn the key without starting 2-3 times (did it to intentionally to move the pulleys a bit) when I actually start chain rattle was severe which never happens on daily normal start. I concluded that when I ran the motor w/o starting oil in the tensiners were being drained and w/o actually running were not replenished w/ system pressure. Just my theory.


Either am I, but what you are saying makes sense to me. I have to go out soon and will take the Z to run my errands. Will report back later. The Z has sat for 2 days, so we shall see!!!

[spork2367]

I also have a Mobil 1 filter, along with the Bosch oil filter to use in the future, but just might try the Napa Gold, like you have...

Both the bosch and mobil 1 are not recommended by Marc as per his last technical posting. He lists the Napa Gold as being good. I tested my Napa Gold and found it to retain 8.2 oz. after 24 hours.

http://www.zr1specialist.com/HAT%20Web/articles/Oil%20Filter%20Recommendation%20Update%202011.pdf

[Roadster]

Both the bosch and mobil 1 are not recommended by Marc as per his last technical posting. He lists the Napa Gold as being good. I tested my Napa Gold and found it to retain 8.2 oz. after 24 hours.

http://www.zr1specialist.com/HAT%20Web/articles/Oil%20Filter%20Recommendation%20Update%202011.pdf

Thank you for the link, have read that before, but was able to pivk up both filters for a decent price. Good to have as spares if necessary.....


My "unscientific" test.....
Started the Z after sitting for 2 days. Turned the key on, waited for 5 seconds and then started. Fired right up, no chain rattle, oil pressure took about 4 seconds to register on the gauge. Did just about a full warm-up and went to the store. Shut down the engine and did immediate restart, (did this twice) one after the other, oil pressure instant and no chain rattle. Went into the store, for about 10 minutes, came out and restarted, 2 second oil pressure delay, no chain rattle. Came home to switch cars in the garage, so another restart was necessary, same as before, good pressure, no chain rattle.
Now there have been times, like when I moved the Z over in the garage on Saturday night, because we were using it on Sunday, and the first start-up was fine, but on Sunday morning, there was chain rattle for about 5 seconds on the start-up.
It appears that if I use the Z and do restarts within a "reasonable" time, the "no chain rattle" is non-existent. But if I let the vehicle sit for an hour or more, the chain rattle makes itself known.....Go figure. Maybe my LT5 has a mind of its own.....
And again, using the GM Blue oil filter.....