wierd noise
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Elder User
Joined: Aug 2000
Posts: 597
Likes: 0
From: Burke VA
wierd noise
Hi all,
Got a 78 with a 351W (rebiult 1000 miles ago), 4 bbl holley, and brand new dual exhaust (no headers) Thing ran good for a couple of months after I installed this engine. All of a sudden the driver's side muffler started to make this rattling noise at idle. It seemed to go away at speed. A mechanic told me that it is either an internal engine problem or the carb is shot. Compression is good. I pulled a plug wire off each of the cylinders on the drivers side and the noise did not go away (I thought that If I had problems in one the pistons the noise would go away if I pulled a plug wire)
I don't see how this could be an internal engine problem, I know my carb is not set up right but would a carb make noise in one of the mufflers?
I'm stumped.
Got a 78 with a 351W (rebiult 1000 miles ago), 4 bbl holley, and brand new dual exhaust (no headers) Thing ran good for a couple of months after I installed this engine. All of a sudden the driver's side muffler started to make this rattling noise at idle. It seemed to go away at speed. A mechanic told me that it is either an internal engine problem or the carb is shot. Compression is good. I pulled a plug wire off each of the cylinders on the drivers side and the noise did not go away (I thought that If I had problems in one the pistons the noise would go away if I pulled a plug wire)
I don't see how this could be an internal engine problem, I know my carb is not set up right but would a carb make noise in one of the mufflers?
I'm stumped.
Senior User
Joined: Nov 2001
Posts: 144
Likes: 1
From: Savannah US
wierd noise
Are you sure it isnt just the muffler? Like the other guy said, maybe a broken baffle inside. Or could be bad exhaust hanger. If it's in the engine you can use a screwdriver as a stethoscope to hear inside the engine. Simply put the screwdriver handle to your ear and the other end on the oil pan, valve covers, intake, or anywhere else.
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
wierd noise
Oft,
George has a good point. The old screwdriver to the ear trick works wonders. Find your self a long screwdriver and take off your tie so as to not get caught up in the belts. Move up and down the valve covers. I use the valve cover bolts to lodge the screwdriver in a steady place. listen to your powersteering, alternator. You'll know it, when you hear it. Get under the truck to see if the exhaust is creating the noise or just channeling it.
KingFisher
George has a good point. The old screwdriver to the ear trick works wonders. Find your self a long screwdriver and take off your tie so as to not get caught up in the belts. Move up and down the valve covers. I use the valve cover bolts to lodge the screwdriver in a steady place. listen to your powersteering, alternator. You'll know it, when you hear it. Get under the truck to see if the exhaust is creating the noise or just channeling it.
KingFisher
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
wierd noise
If it’s originating from the muffler, you should be able to make it rattle yourself. With the engine off, bang on the muffler and pipes with your fist (wear leather gloves it it’s still hot). Everything should feel and sound solid. Try hitting it at different places, angles and rates, if it’s the muffler you should be able to hear the clunks and rattles coming from it. It’s not unusual for a new muffler to break internally, I’ve had two go bad on different vehicles within a few months of replacement, both were defective.
Barry
Barry
