Can't trace an engine noise???
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Can't trace an engine noise???
1967 390 with per the PO about 50000 miles. At first I thought it was an exhaust leak. I looked all over, placed my hand all around the exhaust manifold and can't feel any puffs of air. Thinking it may be valve train related, I took the RH valve cover off and ran the engine, the noise is coming from the front RH side only, I placed my fingers all around the rocker arms, everything seems OK. As the motor was idling w/o the VC, I leaned my ear to 1 & 2 spark plugs and hear the engine noise. When I rev the motor it becomes faster and fainter.
It doesn't sound like a rod or bearing noise. It sounds just like an exhaust leak.
Could it be a cracked piston ring, wrist pin OR a hairline crack exhaust manifold that I'm not seeing????
I had some doubts about the 50000 miles, but the valve train is very clean, no sludge and I'm getting depending on rpm's 50 -20 pounds of oil pressure. After rebuilding the 2100 2 barrel carb, there is no black or blue smoke.
Any suggestions or test????????????
John
It doesn't sound like a rod or bearing noise. It sounds just like an exhaust leak.
Could it be a cracked piston ring, wrist pin OR a hairline crack exhaust manifold that I'm not seeing????
I had some doubts about the 50000 miles, but the valve train is very clean, no sludge and I'm getting depending on rpm's 50 -20 pounds of oil pressure. After rebuilding the 2100 2 barrel carb, there is no black or blue smoke.
Any suggestions or test????????????
John
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I did a compression check and IIRC, it was between 160 -142. On #1&2 it was 142, #5 was the only 160 and the other cyl's about 155-158.
All cyl's held air, no bled out.
Non adjustable rockers, nothing appeared to be cracked or broken. I applied pressure on the rocker arm pushrod end when it was running and the noise did not change. I wiggled the rockers arms and pressed down on the springs and all seemed ok.
PS If it matters here's the correct Comp Test
FRONT of Engine
160 140 Cyl #1
158 140 Cyl #2
152 152
146 152
All cyl's held air, no bled out.
Non adjustable rockers, nothing appeared to be cracked or broken. I applied pressure on the rocker arm pushrod end when it was running and the noise did not change. I wiggled the rockers arms and pressed down on the springs and all seemed ok.
PS If it matters here's the correct Comp Test
FRONT of Engine
160 140 Cyl #1
158 140 Cyl #2
152 152
146 152
Fleet Mechanic
Joined: Aug 2014
Posts: 1,729
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From: Charleston, SC
It's when your motor makes a high lonesome sound.
Kidding. Looks like auto correct turned manifold to mandolin.
Kidding. Looks like auto correct turned manifold to mandolin.
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It's when I use my fat fingers to type on my cell..and it autocorrects...Sorry..
Check the manifold (on the bottom And in between the cylinders) good for a crack or leak...if you can't get in there good ...try some smoke..
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D
Also if you create back pressure by blocking the tail pipe..( and the exhaust system is in decent shape.. ) If there's a leak it should become more noticeable .. Use the smoldering end of a cigarette to see if any air is being forced out the manifold gasket .. ( you'll have to pull the belt for the fan)
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Good ideal about clogging the exhaust pipe.
I've done the smoke thing with the motor off on my mustang, but never with a motor running.
I don't understand what your wanting me to do and how to do it.
I've done the smoke thing with the motor off on my mustang, but never with a motor running.
I don't understand what your wanting me to do and how to do it.
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Disconect fan .. Start truck , block exhaust.. Use the smoke from either a smoke machine or cigarette to see if there any leaks ... The smoke will make the leak visible by showing the turbulence....
Wish we could hear it...
Have you eliminated, power steering pump, water pump bearing, alternator, noisey mechanical fuel pump,.. Do you have an engine stethoscope... About 15 bucks at Autozone..really helps isolate the noise..
Wish we could hear it...
Have you eliminated, power steering pump, water pump bearing, alternator, noisey mechanical fuel pump,.. Do you have an engine stethoscope... About 15 bucks at Autozone..really helps isolate the noise..
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Before I pull the exhaust manifold, I'll get a video.
I still don't understand how you want me to use the smoke method.
What I understand about it, is that you take the carb off, cover the plenum and all other hose openings. Take one vac port and put a hose on it and blow smoke into the manifold, then watch for any trails of smoke coming out for proof off a vacuum leak.
The method I just explained is not what your suggestion.
I still don't understand how you want me to use the smoke method.
What I understand about it, is that you take the carb off, cover the plenum and all other hose openings. Take one vac port and put a hose on it and blow smoke into the manifold, then watch for any trails of smoke coming out for proof off a vacuum leak.
The method I just explained is not what your suggestion.