91 Engine Noise - ZR-1 Net Registry Forums

koshe2 · 01-23-2017

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 · 01-23-2017

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 · 01-23-2017

Quote:

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 · 01-23-2017

could be a stuck tensioner or chains

Hib Halverson · 01-23-2017

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.

32valvesftw · 01-23-2017

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.

We Gone · 01-23-2017

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

ssrszz4 · 01-23-2017

Sometimes mine reminds me of a jet engine when I get on it.

Sent from my XT1585 using ZR-1 Net Registry mobile app

Dynomite · 01-25-2017

I was going to suggest Piston Slap but then koshe2 said "seems to start at 2000 RPM under load"

By the time you put on a load at 2000 rpm Piston Slap usually has disappeared

koshe2 · 01-25-2017

Is that an immediate concern?? I am hearing that its not all that unusual

01-23-2017	#1
koshe2 Join Date: Jan 2017 Location: River Falls, WI Posts: 4	91 Engine Noise 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...

01-23-2017	#2
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,195	Re: 91 Engine Noise 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? __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

01-23-2017	#4
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,195	Re: 91 Engine Noise could be a stuck tensioner or chains __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

01-23-2017	#5
Hib Halverson Join Date: Jun 2005 Location: CenCoast California Posts: 899	Re: 91 Engine Noise 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.

01-23-2017	#6
32valvesftw Join Date: Jun 2015 Location: Texas Posts: 530	Re: 91 Engine Noise 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.

01-23-2017	#7
We Gone Join Date: Apr 2004 Location: ATL. GA. Posts: 2,170	Re: 91 Engine Noise Welcome, All I can say is it takes a bit of time to get use to some of the unique sounds of the LT5. __________________ Steve 1990 Steel Blue/Black #2355 1990 Red/Red #1473 1991 Quasar /Black #118 Sold 1991 Turquoise/Black #766 Parted Out 1993 Yellow/White #179 Sold 1990 Black/Gray #1361 Headers/4:10s Sold

01-23-2017	#8
ssrszz4 Join Date: Jan 2017 Location: US Posts: 233	Re: 91 Engine Noise Sometimes mine reminds me of a jet engine when I get on it. Sent from my XT1585 using ZR-1 Net Registry mobile app

01-25-2017	#9
Dynomite Join Date: Aug 2009 Location: South Dakota/California Posts: 3,812	Re: 91 Engine Noise I was going to suggest Piston Slap but then koshe2 said "seems to start at 2000 RPM under load" By the time you put on a load at 2000 rpm Piston Slap usually has disappeared __________________ Left Clickable links -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 01-25-2017 at 01:34 PM.

01-25-2017	#10
koshe2 Join Date: Jan 2017 Location: River Falls, WI Posts: 4	Re: 91 Engine Noise Is that an immediate concern?? I am hearing that its not all that unusual