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Old 04-03-2009, 09:21 PM
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Roller Cam Thust bearing

I have a 402 BBC full Roller motor with about 2000 miles on it. The other day I drained the oil and found a piece of the crank gear stuck on the magnet. Iulled the front cover and found the gear broke a piece [2 teeth] off the back part of the sproket,the front teeth all in place any I bought a new timing set with torrington bearings and a cam button. When I pulled the cam gear off I found no bearing and a groove in my block, no cam button either. I bought this car with this motor in it already it runs like a bat out of hell around 600hp. anyway my question is do I go ahead and use the torrington bearing with that groove in the block are what should I do. The bearing will cover atleast half of the groove and be flat against the block. The groove is about .035 deep. Any suggestions would be GREATLY appreciated.

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Old 04-03-2009, 11:30 PM
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more info on "grove" - was the groove machined or was it cut by the cam gear against the block. what is the size (relationship) of the grove to the cam gear.
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Old 04-03-2009, 11:39 PM
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Cut in by gear it's about a 1/4" around the cam
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Old 04-04-2009, 12:23 AM
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I would use a solid thrust washer. For the following reasons: thorington bearings sometimes fail, when they do the little rollers end up in the oil pump. Because of the grove, I don't think the thorington will have proper support and may easily fail. normally, when a thrust washer is installed it is necessary to have about .030 milled off the cam gear (block side); this is to accommodate the added thickness of the washer. To check this put your new gear and chain on and check the alignment. I would use a solid cam button nylon or alumn. You may also want to invest in a timing cover that has an access hole for measuring cam thrust clearance, you need about .005 -.008.
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Old 04-04-2009, 03:47 PM
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Quote:
Originally Posted by boobert
I have a 402 BBC full Roller motor with about 2000 miles on it. The other day I drained the oil and found a piece of the crank gear stuck on the magnet. Iulled the front cover and found the gear broke a piece [2 teeth] off the back part of the sproket,the front teeth all in place any I bought a new timing set with torrington bearings and a cam button. When I pulled the cam gear off I found no bearing and a groove in my block, no cam button either. I bought this car with this motor in it already it runs like a bat out of hell around 600hp. anyway my question is do I go ahead and use the torrington bearing with that groove in the block are what should I do. The bearing will cover atleast half of the groove and be flat against the block. The groove is about .035 deep. Any suggestions would be GREATLY appreciated.
Did it have a cam button in it at all? If it didn't the cam's been jumping back and forth in its bearing bore, you'll need to pull it and the lifters to inspect for damage resulting form the lobes slipping sideways to rotation direction which may have taken the lobes and lifter rollers.

The broken gear teeth sound like there wasn't a cam button and the gear was being bound by the cam and it's gear trying to come out of the bearing bore.

The damage to the block would be considered fatal by many people. It is possibly repairable, however. The best repair would be to have the block's cam thrust face milled to remove the gouge, this has to be machining tolerance flat to the block, this is not something you do with a sanding disk with your electric drill. Then a shim made to fill the distance or material removed.

An alternative is that you might be able to squeak by if the edges of the gouge are dressed to smooth and relieve them so they don't cut into a solid thrust washer. The use of a Torrington is out with this type repair. Frankly, I never run Torrington thrust washers, rolling element bearings don't work well in this plane. The distance the inside of any roller travels is less than the outside travels. This means that some or all of every bearing element is sliding relative to the surface under that location. This defeats the purpose of a rolling element bearing making it act like a simple sliding element bearing. Add to that, when one of these fails, the oil pan gets filled with the wreckage which at a minimum gets picked up by the windage and tossed around or worse gets past the pick up screen and into the oil pump. I won't and don't use a Torrington for these reasons.

One must be careful when using any thrust washer between the the cam gear and block, to insure the dimensions of these elements are correct such that the timing gears, and if used, the chain are in proper alignment. And the cam's lobes are under the proper lifter and contact only that lifter and the lifter does not roll on the edge or slightly off the edge of the lobe. Both of these conditions must be met.

Cam buttons, I hate cam buttons they are a PIA, but with engines that don't use a thrust plate they are the easy if not only choice to restrain the cam's adventures. I prefer to use a solid aluminum button. The nylons are nice, but nylon deforms with heat and pressure so your set up slowly gains clearance. On the other hand nylon deforms with heat and pressure, so if you installed it with too little clearance, time and use will correct the situation. I never use rolling element thrust buttons for the same reasons I don't use Torrington style thrust bearings. If you have a failure all those itty-bitty, hard steel rollers are dumped in the oil pan.
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