Cylinder 8 chirps when fired.

regislovato · 02-26-2009, 03:59 AM

After replacing my head gaskets this last weekend, I got my '73 Mustang up and running, and noticed a chirping noise from my engine. I originally thought that the chirping could be from my belt, so I replaced it, but it didn't help. After listening closely, the sound seemed to originate from the mid to rear of the engine on the driver's side. I figure it may be a bad seal to my headers, but it only chirps under load (Although it could still be a leak from the header gasket). while trying to figure out what the problem could be, I decided to disconnect the wire to cylinder 8 for a moment, and the chirping stopped. Now, it had never chirped before I replaced the head gaskets, in fact I replaced the head gasket just to try out some copper ones I had my eyes on for a while.

Now then, I was wondering, would a leaky exhaust header gasket cause a chirp? What about a bad valve? I figure the valves are fine since it never chirped when I ran it before, but the fact that it chirps when it gets a spark under load... ...Let's just say I hope it's not valve related. By the way, I'm running a pretty stock 302.
thanks.

bmxmon · 03-03-2009, 06:19 PM

That sounds pretty odd to me. Have you pulled the spark plug to see what kind of shape its in? Where the head gaskets the same thickness as the ones that came out of it?

regislovato · 03-04-2009, 12:41 AM

my old head gaskets had a compressed thickness of .047 in, but my new ones are slightly flatter, at .043 in when compressed. My block and head surfaces were perfectly flat and clean before I put the gaskets on, and I torqued the head bolts down to 72 ft lbs as specified by my manual, in sequence, in three steps per bolt. My Spark Plugs are brand new, and look fine. I heard somewhere that I should re torque the head bolts after letting the engine cool down after running it until it reaches its normal operating temperature, but others that I have talked to say that's unnecessary.

bmxmon · 03-13-2009, 01:23 AM

Its a good idea to retorque your heads. I think after I built my motor I did it after 3-400 or so miles.
I'm still pretty confused about the chirping noise honestly. Have you checked the rockers and valve train? Perhaps you have a rocker thats too tight or too loose.

jim2f · 03-20-2009, 12:11 PM

How often is the chirp happening. Is it rapid? does it seem to be occuring randomly or is the frequency between the chirps consistant?

02-26-2009, 03:59 AM	#1
regislovato Registered Member Join Date: Nov 2008 Location: Bernalillo, New Mexico Posts: 5	Cylinder 8 chirps when fired. After replacing my head gaskets this last weekend, I got my '73 Mustang up and running, and noticed a chirping noise from my engine. I originally thought that the chirping could be from my belt, so I replaced it, but it didn't help. After listening closely, the sound seemed to originate from the mid to rear of the engine on the driver's side. I figure it may be a bad seal to my headers, but it only chirps under load (Although it could still be a leak from the header gasket). while trying to figure out what the problem could be, I decided to disconnect the wire to cylinder 8 for a moment, and the chirping stopped. Now, it had never chirped before I replaced the head gaskets, in fact I replaced the head gasket just to try out some copper ones I had my eyes on for a while. Now then, I was wondering, would a leaky exhaust header gasket cause a chirp? What about a bad valve? I figure the valves are fine since it never chirped when I ran it before, but the fact that it chirps when it gets a spark under load... ...Let's just say I hope it's not valve related. By the way, I'm running a pretty stock 302. thanks.

03-03-2009, 06:19 PM	#2
bmxmon Registered Member Join Date: Mar 2004 Location: Minnesota Posts: 950	Re: Cylinder 8 chirps when fired. That sounds pretty odd to me. Have you pulled the spark plug to see what kind of shape its in? Where the head gaskets the same thickness as the ones that came out of it? __________________ Alex

03-04-2009, 12:41 AM	#3
regislovato Registered Member Join Date: Nov 2008 Location: Bernalillo, New Mexico Posts: 5	Re: Cylinder 8 chirps when fired. my old head gaskets had a compressed thickness of .047 in, but my new ones are slightly flatter, at .043 in when compressed. My block and head surfaces were perfectly flat and clean before I put the gaskets on, and I torqued the head bolts down to 72 ft lbs as specified by my manual, in sequence, in three steps per bolt. My Spark Plugs are brand new, and look fine. I heard somewhere that I should re torque the head bolts after letting the engine cool down after running it until it reaches its normal operating temperature, but others that I have talked to say that's unnecessary. __________________ -Reggie

03-13-2009, 01:23 AM	#4
bmxmon Registered Member Join Date: Mar 2004 Location: Minnesota Posts: 950	Re: Cylinder 8 chirps when fired. Its a good idea to retorque your heads. I think after I built my motor I did it after 3-400 or so miles. I'm still pretty confused about the chirping noise honestly. Have you checked the rockers and valve train? Perhaps you have a rocker thats too tight or too loose. __________________ Alex

03-20-2009, 12:11 PM	#5
jim2f 65 coupe Join Date: Nov 2005 Location: missouri Posts: 11	Re: Cylinder 8 chirps when fired. How often is the chirp happening. Is it rapid? does it seem to be occuring randomly or is the frequency between the chirps consistant?

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