Throwing this one out there.

[gray85]

I have a strange churping noise coming from the manifold. I did a complete engine overhaul and this noise just recently started, 300mi on the engine.

When I was working on the engine, I plugged the gas line with a wood plug. I had a hard time removing the plug, could have some fragments in the line.

The noise could be coming from the injector/regulator/gas line. Could it be possible that a piece of crap is causing the churping noise?

BTW, engine temp, oil pressure, and idle are all good.

 

[vette-dude]

Well, it could be that missing New Jersey squirrel. Have you tried to listen to it through a stethoscope or long metal tube? You might be able to pinpoint the noise easier. Suspect it is the pressure regulator but maybe someone else can better ID the source.

Randy

 

[warren s]

Hope its not a cam bearing.

 

[Ken]

Have you tried to listen to it through a stethoscope or long metal tube?

Or a long-handled screwdriver, or a length of vacuum hose, or a real mechanic's stethoscope... You get the idea; anything that could conduct soundwaves, etc. and get you closer to the suspected source of noise.

 

[gray85]

Update, I have found the cause of the noise. I put in new aluminum heads, which have moved. The manufacture suggests the heads get re-torqued after the first heat cycle, which I have not done. The heads have a bracket between the intake and exhaust lifters which have a clearance problem. When I installed the heads, the bracket had to be adjusted to allow the lifters to move freely. Since the heads have heated up and moved slightly, I will need to re-torque and re-adjust the brackets.

I understand that aluminum will bend, especially if it is heated up. I have no problems with vacuum leaks or any thing else, just the sound of the lifters rubbing the bracket.

The operation is fairly easy, just time consuming. The exhaust manifolds, value covers, and sparkplugs will have to be removed to get access to the head bolts, which will get re-torqued. Then re-adjust all lifters in question, by removing the rocker arms and moving the bracket.