I looked at a '66 390HP car with someone today. It ran great, but there was a harsh knocking or rapping noise from the front of the engine. At first I thought it was the H20 pump. I put a hose on it and the other end to me ear with the engine running and could hear some noise, but when I put the hose against the timing cover I could tell that's where it was coming from. What could be the cause of this?
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Re: '66 BIG BLOCK RAPPING NOISE IN TIMING COVER
Worn gears and a loose timing chain whapping the timing cover... -
Re: '66 BIG BLOCK RAPPING NOISE IN TIMING COVER
Interesting, supposively he rebuilt the engine 500 miles ago. I'll ask him if he installed a new timing chain set when he did the rebuild. Other than one of the bolts that hold the sprocket to the cam coming loose, I guess there's nothing else it could be. Sounds like an expensive repair.Comment
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Re: '66 BIG BLOCK RAPPING NOISE IN TIMING COVER
Rob, Check for noise at fuel pump housing, especially if it is an aftermarket fuel pump. Possible broken, missing or weak spring on fuel pump actuating arm?
DaveComment
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Re: '66 BIG BLOCK RAPPING NOISE IN TIMING COVER
Rob,
I ran into something like this and it turned out that the cam was "walking". In other words it was moving back and forth and hitting the timing cover. First attempt to fix was a new timing chain and gears along with a cam button which is supposed to minize walking effect. Evetually though, it proved to be a worn cam shaft which had to be replaced.
TedComment
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RE:'66 BB RAPPING NOISE IN TIMING COVER
The owner showed me recepits for the new cam, lifters and timing gear set he installed. I thought it might be the cam sprocket bolts coming loose, but he said he used locktite and torqued them. With less than 500 miles on the rebuild, what would make the cam or timing gear set wear so quickly as to cause the chain(which I assume it is) to be hitting the cover? I thought the lifters and cam were made in such a way as to rotate the lifters while maintaining enough pressure to prevent forward movement enough to cause this.Comment
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Re: RE:'66 BB RAPPING NOISE IN TIMING COVER
Rob - could he have used some aftermarket gearset that was wider than stock, and possibly is too close to the cover? I haven't really seen issues with this, but just thinking out loud. It is hard to belive the chain has worn in that length of time. You are right, cam walk is associated with roller tappets, a flat tappet cam pulls rearward. Maybe the timing cover has been "bent" in somewhere in the path and has a localized clearance problem too. CraigComment
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Re: RE:'66 BB RAPPING NOISE IN TIMING COVER
Craig,
I guess I'll be pulling the cam. Wish the noise could be something else, but it's really localized to the timing cover, and I'm sure it won't go away on its' own. The thing is, with the cam, lifters and timing set being alwost new, I'm not sure what I'll do different with the new installation of these to prevent it again. Will I(or someone)be able to tell by looking at them after removal why the problem occurred?Comment
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Re: RE:'66 BB RAPPING NOISE IN TIMING COVER
Rob - there should be telltale wear marks where the rubbing is occuring. I am guessing you won't find excessive stretch in the chain, but this is a guess. I would carefully evaluate before any reassembly. Nothing is rocket scinece here, these things happen for simple reasons, and it should be obvious once apart. Good luck!........CraigComment
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Re: RE:'66 BB RAPPING NOISE IN TIMING COVER
I noticed today, that when I turn the engine over by hand with a wrench on the crankshaft balancer bolt, that I can hear a scraping during one point in the rotation. I'll assume that's the point when the cam is moving forward more than it should and allowing the chain to contact the cover....
Thanks,Comment
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Re: '66 BIG BLOCK RAPPING NOISE IN TIMING COVER
Dave,
I'm interested in your suggestion regarding the fuel pump push rod. I understand the rod operates off the first cam lobe, which could account for the noise sounding from the timing cover. I assume I have to remove the pump to determine if it is the problem. It is an original AC pump. I assume this happened to you, how did you finally determine it was the pump push rod? I'm hoping that's my problem, rather than dropping the oil pan, removing the timing cover and discovering nothing wrong.Comment
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Re: '66 BIG BLOCK RAPPING NOISE IN TIMING COVER
Rob -
Remove the fuel pump, pull the pushrod all the way down (so it won't contact the drive lobe on the cam), and start the engine and let it run on the fuel in the float bowl. If the noise is gone, you've found the problem.Comment
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Re: '66 BIG BLOCK RAPPING NOISE IN TIMING COVER
Rob, John's suggestion is an excellent way to find out for sure. The noise is caused by too much clearance between the fuel pump arm and push rod, when the spring is weak, missing, or broken. DaveComment
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