Why would a BBC "eat" distributor gears?
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Why would a BBC "eat" distributor gears?
It's a 454 from a friend's '85 Silverado pickup. He got the engine freshened up and it's eaten two distributor gears in the past month--each requiring a complete teardown and cleaning.
The oil pump is a new "stock"-type standard volume, standard pressure unit. The cam is a new hydraulic flat-tappet, so there should be no need for a special distributor gear.
The first distributor gear that got eaten was the original that had worked fine with for upwards of 100,000 miles. The second was brand-new and it lasted about a week.
The distributor is shimmed correctly and hasn't been touched since it came out of the "old" engine. The oil pump spins freely and the distributor drive shaft is new, straight and apparently perfect.
The only thing we can figure is that the gear on the cam is machined incorrectly somehow. Anyone have any other ideas?
[Modified by The Dude, 4:43 PM 1/30/2004]
The oil pump is a new "stock"-type standard volume, standard pressure unit. The cam is a new hydraulic flat-tappet, so there should be no need for a special distributor gear.
The first distributor gear that got eaten was the original that had worked fine with for upwards of 100,000 miles. The second was brand-new and it lasted about a week.
The distributor is shimmed correctly and hasn't been touched since it came out of the "old" engine. The oil pump spins freely and the distributor drive shaft is new, straight and apparently perfect.
The only thing we can figure is that the gear on the cam is machined incorrectly somehow. Anyone have any other ideas?
[Modified by The Dude, 4:43 PM 1/30/2004]
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Re: Why would a BBC "eat" distributor gears? (The Dude)
Odd problem. Well after 2 gears I would pull the cam at least to look at it good. Hard to believe there would not be some damage on that gear as well. Maybe the gear was not centered up perfectly? Thought I remembered something about a special distributor gear needed if the cam is steel VS. a cam that is cast?
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Re: Why would a BBC "eat" distributor gears? (The Dude)
Roller cam gears will eat up regular distributor gears if the wrong cam gear is used...
Car Craft March 2k4, paraphrased: Roller cams are generally made from steel, rather than iron which flat-tappet cas use. The steel of the cam drive gear will eat up an iron distributor gear in a hurry. Bronze gears are the right solution in this case.
Chevrolet used a steel distributor gear that are treated with a special coating."
Does that give any insight? Look into steel or bronze distro gears.
-Steve
Car Craft March 2k4, paraphrased: Roller cams are generally made from steel, rather than iron which flat-tappet cas use. The steel of the cam drive gear will eat up an iron distributor gear in a hurry. Bronze gears are the right solution in this case.
Chevrolet used a steel distributor gear that are treated with a special coating."
Does that give any insight? Look into steel or bronze distro gears.
-Steve
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Re: Why would a BBC "eat" distributor gears? (The Dude)
Yeah, it is probably the cam's fault, I'd check with the manufacturer of the cam and see which gear they recommend. The problem with using a hardened gear on a iron camshaft, is that it can tear up the cam gear. Chevy does have a special "Mellonized" cam gear that they use on roller cam motors.
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Re: Why would a BBC "eat" distributor gears? (Smokehouse69)
You said the gear was good for 100K miles, it may have developed a wear pattern that caused it to fail on the new cam. There are other possibilies: distributor pad on intake manifold height changed causing problems, oil pump causing problems, mis alignment of intake manifold opening (rare case occurance but can happen), cam has problem. I would definatley look at the cam gear and check distributor mounting height, My 2 cents.
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Re: Why would a BBC "eat" distributor gears? (The Dude)
Thanks for the ideas. I'll pass them along. It's gotta be something with the cam--it's your plain-vanilla hydraulic flat-tappet kind of thing but it's new. And, yes, the cam gear has to be trashed now that it's eaten two distributor gears. (I haven't seen it personally, just relating an anecdote.)
