1999 L31 Engine with nearly 260k, Timing chain plus what else?

[Road Trip]

Just a heads up on the Holley cover- not sure if anyone else has experienced this, but it seems as if the aluminum cover acts as an amplifier for chain noise... Just buttoned an engine all back up and went with the Aluminum cover... you can hear every little rattle that chain makes with the holley cover. I tore back apart and changed chain set to be sure it wasnt too sloppy...new cloyes deflection was imperceptibly different to the 150k mile roller that was on it...and not a whole lot different than the last one I tore down. Thinking about going back with the plastic.

Edit- sounds like a metal rattle at idle... Removed drive belt and no change to noise. Checked inside of cover for witness marks and chain didnt appear to be hitting inside of cover.

Wow. Wondering if there's room for a layer of carefully-trimmed Dynamat on top of that cover?
I was really thinking of upgrading to that aluminum cover down the road, but at the same time
I don't want to amplify the chain noise? Thanks for the heads-up based on your firsthand experience!

You've done this? And saw the behavior you described?

Closest I've gotten in person was careful observation of ignition timing jumping all around on a
SBC with a suspected loose timing chain. (When you got to certain engine speeds the ignition timing
was chaotic looking -- most folks were blaming this on the timing light itself?)

After replacing the worn-out factory chain with a Cloyes True Roller, using the same timing light,
the spark advance was *way smoother* when held at a steady rpm, even at the speeds where
the harmonics were previously making the sloppy chain really flutter?

Needless to say, the engine ran both smoother & quieter. Of course this was before GM had
added the CKP and CMP sensors so that we can see this directly (see attached #1) instead of
inferring it from using a stroboscopic timing light to 'freeze' a mark cut on the harmonic balancer.

...but I've been seriously considering doing exactly what I described on my '99 L29 using my
own trusty Tek 475. (The thought process was to compare real time scope readings to what
the scan tool is averaging out to a single CMP Ret #.)

EDIT: A scope is a very useful tool for making sense out of mysteries under the hood. If you
haven't already seen this, here I'm testing out a Knock Sensor that we added to an engine
being built for lots of boost. I've used the 475 as a last resort in order to fix a lot of the
'resisting repair' problems, but AFAIK this is currently the only video of it in use.
(Knock Sensor waveform test - old video, 2010-era picture quality.)

Listen, if you do hook up your scope, be sure to take a short video and share the wealth. I've
had a hankering to do this, and would have accomplished it already, except for packing for the
upcoming move is stealing precious time away from the good stuff like this.

BTW, good to know there's at least one other Tek 475 enthusiast still in the game. :0)

Fascinating idea

I'll have to pull out the old Tektronics 475 and give this a whirl.

 

[Orpedcrow]

I’d love to have a scope for the shop

 

[Danimal08]

Updates: If you want to be alerted to the fact that you have a bad chain, install a Holley cover. Put new cloyes C3017 set on it and shes quiet as a church mouse with the Holley cover.

While I had the new to me engine apart cleaning it all up and resealing, I regretfully skipped a new chain set. Had some slack but no more than the last one that was in it and it was quiet so I figured it would be fine. Oops.

I will say it was about a PITA to put a new pan gasket on it with it in the truck. Was able to do without pulling diff, but what a mess trying to move cooler and lines, etc. You will definitely need to lower the pan to get the holley cover on.

 

[99xcss4]

glad to hear that you figured it out and fixed it and we all got to learn some thing as well if you have a bad chain you will hear it with the holley cover not with the plastic one

 

[1998_K1500_Sub]

Updates: If you want to be alerted to the fact that you have a bad chain, install a Holley cover. Put new cloyes C3017 set on it and shes quiet as a church mouse with the Holley cover.

Sorry, I'm a bit confused. Earlier you said:

Just buttoned an engine all back up and went with the Aluminum cover... you can hear every little rattle that chain makes with the holley cover. I tore back apart and changed chain set to be sure it wasnt too sloppy...new cloyes deflection was imperceptibly different to the 150k mile roller that was on it.

So, if I understand, you tried two chains, one of which was a new Cloyes, and yet you still heard chain noise. Yes?

Then...

Put new cloyes C3017 set on it and shes quiet as a church mouse with the Holley cover.

So you tried a 3rd Cloyes chain (C3017) and you're reporting that it's better now. Yes?

So the other two chains, one of which was a new Cloyes, were noisy, but the third, a Cloyes C3017, is not. Did I get that right?

 

[99xcss4]

Sorry, I'm a bit confused. Earlier you said:



So, if I understand, you tried two chains, one of which was a new Cloyes, and yet you still heard chain noise. Yes?

Then...



So you tried a 3rd Cloyes chain (C3017) and you're reporting that it's better now. Yes?

So the other two chains, one of which was a new Cloyes, were noisy, but the third, a Cloyes C3017, is not. Did I get that right?

yes you got it right or at lest I think so that what it sounded like to me that it is fixed now

 

[1998_K1500_Sub]

But then he said:

Tried three different timing sets on it and all were what I would consider sloppy. I'll report back if the silent type helped.

So was the last of the three the "silent type"? Was that the Cloyes C3017 chain? And it's no longer noisy?

I like the story but there's a bit of ambiguity. For example, I read this:

alerted to the fact that you have a bad chain, install a Holley cover.

So the first Cloyes set, which was new (yes?) and reportedly noisy (yes?), is a "bad chain"?

 

[99xcss4]

I was just thinking dose any know why gm thought it was a good idea to use a plastic timing cover to me it seems like they were cheaping out and the fact that you have to replace it every time it is removed is money down the $#!+er if you ask me

 

[Danimal08]

Sorry, I'll clarify here...this project has been a bit of a saga for even me to keep straight.

I bought a used engine for my project truck a few weeks back after finding that my engine was pretty much toast.

I cleaned up, repainted, resealed, etc the used engine. While it was apart during that process, I opted to leave the timing set as-is, and I installed a new holley cover. I got the engine back in and all new accessories installed. When I fired it up, it was noisy. Sounded like steel marbles rolling around.

I pulled all back apart while it was in the truck, and it was fairly loose, but not any more so than the other 350 I have. I swapped the old motor chain to the new motor and it was also loose. So I opted to by the c3017 set which is the quiet type chain. It still seemed loose but mildy better. It is now all better with the holley cover.

Edit: I've tried to Chronicle my project here... https://www.gmt400.com/threads/hello-all-new-here-with-a-new-project.57441/

 

[1998_K1500_Sub]

@Road Trip, are you acquainted and reasonably proficient with KVL analysis?


Nice, clean Tek 475 you have Mine doesn't have the top-mounted DM-40 DVM.

I've also got a Tek 2465A four channel and a Heathkit two channel (the handle's in the way in the picture). The 2465A is my go-to 'scope, I've used it (or one like it) for almost 40yrs.