I fired up the engine my F100 after it has sat for a couple decades. I have an exhaust chirp coming out the end of the tailpipe. I originally figured I had built a whistle inside somewhere from welding slag perhaps. I've had numerous people look and listen and no-one is able to tell me what it is. Until my buddy Dave came over this morning. He listens and tells me he had a similar problem back when he wore a young man's clothes. He used to work all winter up north in the bush as a surveyor. They would leave their trucks run all winter so they didn't freeze to death, and his truck had a chirp like this when he went home in the spring. His mechanic was an older fella and he listened to it, then made a flapper out of a thin piece of cardboard. He bent the cardboard so it could very easily bend back and forth. He held it close to the end of the tailpipe when it was running and it would suck back at the end of the pipe, then blow it out again, very rapidly. We did the same thing with my truck and guess what. The cardboard flaps back and forth just like he said. Dave told me he had to do the valve guides as they had extreme carbon deposit, and wore out. The mechanic said it would chirp when it pulled air back up the tailpipe. I'm thinking I might have to do a head replacement. Anyone ever heard of this? Oh, it's a 300 Ford six cylinder. The engine came from a much newer truck that was only used inside a fertilizer plant. Engine only had 32,000 miles on it, but probably several years worth of idling time. Truck was so rusted out that the drivers door fell off it when I brought it into the shop to pull the motor. It was never registered to drive on public roads, just inside the fertilizer plant.
I did a compression test. 1 is 115, 2 is 120, 3 is 125, 4 is 130, 5 is 120, and 6 is 115 lbs. Would I have compression this good if I had a burnt valve? I can take most stuff apart and put it back together again. I can make most anything out of sheet metal. I am a piss poor tune up mechanic. Please help.
Did you do a compression test after a squirt of oil into the cylinder? This will tell if the leak is past your valve, not your rings.
I had a burnt exhaust valve on a Ford 200 I6. It had a lumpy idle because of it. Squirting oil didn’t change the compression so off came the head. One of the exhaust valves was burnt like someone took a bite out of it. All the intake valves were fine. I got all new exhaust valves because after grinding them, they were too close to the minimum spec. The log head didn’t have replaceable valve guides so I knurled them and ground the valve seats. It was a little easier to work on than a 300 but mainly since the head was much lighter.
No oil squirted into any of the cylinders. Didn't know that was necessary or required. Thanks for the replies though. I'm going to just drive it for a bit regardless, and probably buy a new head.
Most time a compression test out good , but not 100%, Use a stethoscope , I have had bad severe wear on valve stem & guide Not show up on compression test, When engine Running valve searching to center up on seat . (Noise)
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