Engine Noise - The 1947 - Present Chevrolet & GMC Truck Message Board Network

VDOG · 12-27-2009, 04:31 PM

Ok it sounds like a bad miss or exhaust leak.
At idle, or in Park if I rev the engine is sounds normal. Once I put the truck in gear, D or R, and put a load on it, then it sounds like a bad sputter or miss, and its loud. It sounds like its coming from the passenger side of the motor by the head but I cant detect any air leaks.
Had my exhaust checked, and there are no leaks.
Help

**Stocker** · 12-27-2009, 04:43 PM

Flat cam lobe??

Sinister · 12-27-2009, 04:45 PM

Ignition?

cdowns · 12-27-2009, 06:24 PM

if you have the original type exhaust i'd think the donu where the manifold meets the pipe is burned out

Wrenchbender Ret · 12-27-2009, 06:49 PM

Sounds like an exhaust leak around one of the ports. If it shakes at idle when in gear it's probably a bad valve.

*2tons of fun* · 12-27-2009, 07:04 PM

burned head gasket between the cyliders.

68gmsee · 12-27-2009, 08:10 PM

Just to get the symptoms straight.

A miss is caused by a misfiring from the ignition or fuel system and you can here it as an intermittent sound. A sputter is similar but is a rapid sound almost like when you put your lips together and blow air threw them. At least that is the way I would describe it.

But, regardless, I don't have a clue.

I'd first check what's been recommended and maybe see if you can have someone put the parking brakes on and you stand by the engine while they shift it into gear.

Maybe even use the NDD tool (noise detecting device). I use a 3 foot piece of hose garden hose but any hose will do. You may be able to isolate it further to a certain location.

69GMCLonghorn · 12-29-2009, 07:39 PM

Classic case of header leak at the head... To test it, you need to have a friend that you can trust, get in it, drop it in drive with the foot on the brake. Have him do a "slight" brake stand to get some load on the engine while you stand off to the side of the vehicle and try to hear exactly where the noise is coming from. I'll bet you discover a bad manifold gasket... or loose header bolts.

**Stocker** · 12-29-2009, 07:46 PM

Quote:

Originally Posted by 69GMCLonghorn

Classic case of header leak at the head... To test it, you need to have a friend that you can trust, get in it, drop it in drive with the foot on the brake. Have him do a "slight" brake stand to get some load on the engine while you stand off to the side of the vehicle and try to hear exactly where the noise is coming from. I'll bet you discover a bad manifold gasket... or loose header bolts.

Yes -- and this works best with a stone cold engine.

VDOG · 12-29-2009, 09:09 PM

Bad Mainfold gasket, never thought of that. Header bolts are tight but I will check again. Manifold gasket did have a large amout of oil on top passenger side.

pat 70/71 · 12-29-2009, 10:32 PM

sounds real basic so forgive me, change out the spark plugs& then the wires if needed i have had the same thing kick my butt in the past only to find it was a fouled plug not a pro just trying to help ...Pat

echo72 · 12-29-2009, 11:05 PM

When I bought my truck, I had the same problem. My manifold exhaust gaskets were shot to the curb. After I replaced them, the problem went away.

tcrist · 06-15-2014, 12:29 PM

One thing that I have always done on headers with the thin flanges is cut the flange between the first and second, third and fourth cylinders (I.E. for a SBC, between 1&3, 5&7. 2&4, 6&8). Thin flange headers tend to warp after time then it is hard to keep them tight. You can also use the locking header bolts http://www.jegs.com/p/Stage-8/Stage-...49275/10002/-1 .

12-27-2009, 04:31 PM	#1
VDOG Grand PooBaa Member Join Date: Jan 2001 Location: LA, CA Posts: 5,302	Engine Noise Ok it sounds like a bad miss or exhaust leak. At idle, or in Park if I rev the engine is sounds normal. Once I put the truck in gear, D or R, and put a load on it, then it sounds like a bad sputter or miss, and its loud. It sounds like its coming from the passenger side of the motor by the head but I cant detect any air leaks. Had my exhaust checked, and there are no leaks. Help

12-27-2009, 04:43 PM	#2
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,668	Re: Engine Noise Flat cam lobe?? __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

12-27-2009, 04:45 PM	#3
Sinister Between Trucks... Join Date: Mar 2002 Location: Los Angeles, CA. Posts: 3,830	Re: Engine Noise Ignition? __________________ Beat it to fit, Paint it to match...

12-27-2009, 06:24 PM	#4
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Engine Noise if you have the original type exhaust i'd think the donu where the manifold meets the pipe is burned out __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

12-27-2009, 06:49 PM	#5
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,226	Re: Engine Noise Sounds like an exhaust leak around one of the ports. If it shakes at idle when in gear it's probably a bad valve.

12-27-2009, 07:04 PM	#6
2tons of fun Account Suspended Join Date: Jan 2009 Location: galt ca, Posts: 749	Re: Engine Noise burned head gasket between the cyliders.

12-27-2009, 08:10 PM	#7
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Engine Noise Just to get the symptoms straight. A miss is caused by a misfiring from the ignition or fuel system and you can here it as an intermittent sound. A sputter is similar but is a rapid sound almost like when you put your lips together and blow air threw them. At least that is the way I would describe it. But, regardless, I don't have a clue. I'd first check what's been recommended and maybe see if you can have someone put the parking brakes on and you stand by the engine while they shift it into gear. Maybe even use the NDD tool (noise detecting device). I use a 3 foot piece of hose garden hose but any hose will do. You may be able to isolate it further to a certain location.

12-29-2009, 07:39 PM	#8
69GMCLonghorn Registered User Join Date: Dec 2006 Location: Porter Ranch, CA Posts: 978	Re: Engine Noise Classic case of header leak at the head... To test it, you need to have a friend that you can trust, get in it, drop it in drive with the foot on the brake. Have him do a "slight" brake stand to get some load on the engine while you stand off to the side of the vehicle and try to hear exactly where the noise is coming from. I'll bet you discover a bad manifold gasket... or loose header bolts.

12-29-2009, 09:09 PM	#10
VDOG Grand PooBaa Member Join Date: Jan 2001 Location: LA, CA Posts: 5,302	Re: Engine Noise Bad Mainfold gasket, never thought of that. Header bolts are tight but I will check again. Manifold gasket did have a large amout of oil on top passenger side.

12-29-2009, 10:32 PM	#11
pat 70/71 Registered User Join Date: Nov 2009 Location: newbury park california Posts: 1,038	Re: Engine Noise sounds real basic so forgive me, change out the spark plugs& then the wires if needed i have had the same thing kick my butt in the past only to find it was a fouled plug not a pro just trying to help ...Pat

12-29-2009, 11:05 PM	#12
echo72 Registered User Join Date: Feb 2009 Location: Hampton, GA Posts: 76	Re: Engine Noise When I bought my truck, I had the same problem. My manifold exhaust gaskets were shot to the curb. After I replaced them, the problem went away. __________________ Every day is a challenge. Keep on truckin! 1972 Chevy Cheyenne LWB 350 engine TH400.

06-15-2014, 12:29 PM	#13
tcrist Registered User Join Date: May 2014 Location: Manteca, Ca. Posts: 274	Re: Engine Noise One thing that I have always done on headers with the thin flanges is cut the flange between the first and second, third and fourth cylinders (I.E. for a SBC, between 1&3, 5&7. 2&4, 6&8). Thin flange headers tend to warp after time then it is hard to keep them tight. You can also use the locking header bolts http://www.jegs.com/p/Stage-8/Stage-...49275/10002/-1 .



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