Cam bearing issue
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Lead Driver
Joined: Mar 2008
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From: Near Los Angeles
Cam bearing issue
My mechanic is assembling my engine. When inserting the Isky cam into the block/new bearings, the second bearing was too tight, and he couldn't get the cam through. He tried forcing it with a rubber mallet, then pulled it out. I could feel a lip/ridge where the shaft had entered the bearing about 1/4th of the way.
He then used 320 wet/dry sand paper to sand off the ridge, and the rest of the bearing surface, then sanded with 600 grit, and the cam went right in, through all the bearings. But this worries me, to say the least.
I grew up around mechanics, and was always told you never touch the surface of a bearing with anything other than lube and the part that it fits around. Although my mechanic says he has done no harm by sanding the bearing, to my thinking he has just put 80,000 miles wear on that bearing, and sanding through the protective alloy layer of the bearing.
Although my mechanic says it will be fine, and the machine shop says it put the original cam in to test the fit of the bearings and to insure the new bearings were properly installed, I want to take it back and have them r&r the sanded bearing with a new one.
Does anyone have experience with this sort of thing, or knowledge about 'sanding' a bearing?
Should I have it r&r'ed, or stay with the modified bearing?
Thanks.
He then used 320 wet/dry sand paper to sand off the ridge, and the rest of the bearing surface, then sanded with 600 grit, and the cam went right in, through all the bearings. But this worries me, to say the least.
I grew up around mechanics, and was always told you never touch the surface of a bearing with anything other than lube and the part that it fits around. Although my mechanic says he has done no harm by sanding the bearing, to my thinking he has just put 80,000 miles wear on that bearing, and sanding through the protective alloy layer of the bearing.
Although my mechanic says it will be fine, and the machine shop says it put the original cam in to test the fit of the bearings and to insure the new bearings were properly installed, I want to take it back and have them r&r the sanded bearing with a new one.
Does anyone have experience with this sort of thing, or knowledge about 'sanding' a bearing?
Should I have it r&r'ed, or stay with the modified bearing?
Thanks.
Elder User
Joined: Jan 2009
Posts: 774
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From: East Tennessee
Sorry to hear that. Don't you hate when someone does something stupid like that? My dad is one of the best mechanics I've ever known, but one time, I had this EXTREMELY hopped up Dodge Stealth R/T Twin Turbo. I had bought a $1000 forged steel crank for it, and I eventually spun a rod bearing (only took a few weeks, lol, weak stock rods, imo). My dad was helping me fix it this time, and he came to my garage when I wasn't there, and sanded down the crank!!! I was so pissed. After putting it all back together, it lost oil pressure on the first rev... then I sold it.
Elder User
Joined: Oct 2008
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Wear on cam bearings that are properly set up is almost zero. They would probably last 2 or 3 engine rebuilds. And sanding down a cam bearing that 'felt tight' is probably alright. But cam bearing are precision items, with a preset amount of crush designed into them. If your cam would not go in at all it was either the wrong one, the edge was not chamfered, or it was very slightly cocked in it's bore. I don't believe that once an edge is raised that the bearing can technically be 'fixed', it might be functional, but not fixed. What kind of a mechanic takes a hammer to a camshaft installation anyway? It doesn't matter if it's a soft mallet, might as well be a sledge hammer in this situation. They bothered to press it in for you, can't they press it back out and remeasure? If they measured in the first place at all. I would politely say that you need it replaced. Then not use that machine shop again.
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Lead Driver
Joined: Mar 2008
Posts: 7,182
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From: Near Los Angeles
I contacted a mechanic I grew up with. He is now a professional performance engine builder. He said he has had the same problem before, and sanded the bearing with 600 grit. If there were no marks in the bearing, it will be fine. However, he said that if it was a v8 he would replace it. But since it is a inline 6, it takes less load due to the extra
journal.
The bottom line is that I trust him.
journal.
The bottom line is that I trust him.
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