91 Engine Noise

[koshe2]

I just bought a 91 ZR1 with 115K miles. 6 speed Has this knock when its cold, at engine speed. It goes away for the the most part when its warm. Does not rattle at idle, but seems to start at 2000 RPM under load. Sounds like a lifter, Injectors have been replaced at one time.

I live near St Paul MN and would like to have this checked out. I am not super worried as it calms down when warmed up. Oil pressure looks just fine.

Where do I start? Suggestions??

Not sure what oil is in it. Not sure what to uses. 10-30 mobile 1??

I am new to this forum...

[LGAFF]

knock or tick? Did you try pulling plug wires to see if there is one that does not change the issue when a wire is pulled?

[billschroeder5842]

Originally Posted by koshe2

Has this knock when its cold, at engine speed. It goes away for the the most part when its warm. Does not rattle at idle, but seems to start at 2000 RPM under load.

I live near St Paul MN and would like to have this checked out. I am not super worried as it calms down when warmed up. Oil pressure looks just fine.

Welcome to ZR1 Land!

Is there any way you could post a video w/sound?

Sounds are tough to diagnose over the web as one mans Knock is another mans clunk.

Also, if the sound goes away when warm, does it make sense to let the engine warm up a bit longer before putting it "under load?" Our LT5s like to be warmed up and fully lubricated. The fact that you mention that the sounds goes away when warm is your biggest clue that you may be driving the car before it's ready.

Minnesota is WAY cold and your engine is probably needs a few moments.

[LGAFF]

could be a stuck tensioner or chains

[Hib Halverson]

As suggested earlier, it's hard to diagnose noises via the I'net.

They way you describe it in the OP, I'd say it's not any chain tensioner issue.

Could be cold piston knock which is common with the LT5. Cold piston knock is really not a "knock" like a "rod knock" it's more like a "fluttering" lifter noise at low rpm under load which goes away when the engine warms to operating temperature.

I guess we're going to need either a better description of the noise or an audio file to offer more information.

[We Gone]

Welcome, All I can say is it takes a bit of time to get use to some of the unique sounds of the LT5.

[32valvesftw]

Carefully use a long screwdriver like a stethoscope put your ear to the handle you will be able to get a good idea of what section of the engine its coming from. Also have you done a recent oil change, if not maybe do so and look for metal dust or bits in the oil. Noises like that time to find.

[Hib Halverson]

Originally Posted by 32valvesftw

Carefully use a long screwdriver like a stethoscope put your ear to the handle you will be able to get a good idea of what section of the engine its coming from. Also have you done a recent oil change, if not maybe do so and look for metal dust or bits in the oil. Noises like that time to find.

Much better than the screw-driver-handle-in-ear tool is a real mechanic's stethoscope. The sound transmission is far better. One of the better units available, and the one I use in my shop, is made by Lisie PN 52750. You can find it at RockAuto.com for around 16 bucks

Also, unless your oil filter is fully bypassing, you're not going to find any powder in the oil. If you find "bits" in the drain oil, you have far worse problems than cold piston knock and need to get the motor out for repair.

[koshe2]

It gets better when the oil warms up, but its still there. Sounds like a lifter.
Has 10-30 mobile 1 and a wix filter

[Hib Halverson]

Without hearing it I'd say it's cold piston knock, which some call piston "slap".

A certain amount of cold piston knock is typical of LT5s. It should almost go away entirely when the oil temperature is normal.