Need some help identifing this engine noise?

CAPTKEV85

Petty Officer 1st Class
Joined
Mar 12, 2008
Messages
229
Hello everyone.
I purchased this Marine motor remanufactured chevy 350 small block with Roller Rocker cam and vortec heads from Michigan Motorz. From oil pan to carb is brand new cost was about $7700.00 Now I am getting this clacking ticking or knocking noise from the engine at idle. And it is intermittent, it seems to be worse after you run the boat at normal operating range (which I run 2400 rpms) and return to idle then shut engine off. When it restarts that noise will come back. Now it seems once you rev engine it will go away and sometime will not return at idle. No I am disappointed with Michigan Motorz because the engine started to have this noise at approx. 30 hours on it. It now has 75 hours. They made me do a compression test on all cylinders at operating temp. 205 psi range for all 8cyls. Also had sent them pictures of the spark plugs which all has the same normal color and wear, They said they will look into it and now 5 emails later and phone calls and no response from them and the 1 year warranty has expired. I run royal purple oil sae40 with and tall oil filter and change twice a season. The motor runs smooth and wot is 4400 rpms. I am just concerned with this noise. Any advice will help. thanks
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
Sounds like it could be valvetrain noise. Maybe a lifter not pumping up.
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,779
Exhaust shutter - have you listened with a stereoscope or screw driver to the ear?
 

CAPTKEV85

Petty Officer 1st Class
Joined
Mar 12, 2008
Messages
229
today I am going to pull the valve covers and see if there is any valve lash. Then I am going to readjust them and maybe it will go away. I hope its not a lifter because I will have to pull manifold. Should I be concerned that this motor will grenade?
 

pro-crastinator

Chief Petty Officer
Joined
Dec 12, 2013
Messages
453
hydraulic lifter. - but which one?
get a mechanics stethescope ($4.00 chinese tool company?) and listen to each lifter with covers off at idle.
The screwdriver to the ear also works but the stethescope is amazing.
 

CAPTKEV85

Petty Officer 1st Class
Joined
Mar 12, 2008
Messages
229
I am going to purchase one. I don't know which lifter yet but its coming from port side of engine.Cyl 1 side. Would a timing chain tensioner make this noise?
 

harleyman1975

Ensign
Joined
May 12, 2003
Messages
959
Don't think SBC has a tensioner unless valve train has been modified. I think it is a lifter as well. Would I fix it? yup but only because I would be embarrassed by the noise not because I would be afraid of it blowing up.
 

CAPTKEV85

Petty Officer 1st Class
Joined
Mar 12, 2008
Messages
229
Ok I did a valve adjustment. The build sheet says it has a gm marine roller cam with roller lifters. But the rocker arms seem to be flat tappet. Is this normal? I'm contacting the engine manufacturer today because a motor with 77 hours shouldn't make noise like this. below is valve train video
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,779
Yeah roller cam motors don't have roller rockers. Did the noise change after adjusting the lifters?
 
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