what could cause this ??? - Team Camaro Tech
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post #1 of 3 (permalink) Old Feb 8th, 08, 05:44 PM Thread Starter
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what could cause this ???

in my 383 stroker (5.7 Rods) scat crank, clearanced rods, using a Summit cam# sum 1103. It had a wierd "rapping noise" in the engine since I installed this cam,(didn't have it with the previous Comp Cams cam). was loud when cold & almost go away when it warmed up. I figured a lifter. (they're new) but when it was cold & I drove it next to a concrete wall, it almost sounded like a rod knocking ! but went away when warmed up. (& holds Great oil pressure even when hot). ANYWAY, I pulled the cam today to check it for worn lobes, there is nothing wrong, (all the same lift) BUT...the 7th LOBE back from the front (#3 exaust) looks like something HIT it FROM THE SIDE & pushed a small bump of metal UP onto the ramp of the lobe. this motor as I said Has clearanced rods, & nothing was even close when I spun it aroung before buttoning it up! i BELIEVE THE CLOSEST ROD TO THAT LOBE IS #4, BUT IF THE ROD WAS TO HIT THE CAM, IT LOOKS LIKE IT WOULD HIT IN THE CENTER OF THE LOBE, not a glancing blow from the side towards the outer part of the lobe. hard to describe. Has anyone here ever run into such a thing ? thanks for your help.
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post #2 of 3 (permalink) Old Feb 8th, 08, 06:43 PM
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Re: what could cause this ???

One never knows what goes on inside the crankcase. It could very well be a rod bolt hitting and the effect is what you are seeing/hearing on #7 lobe.

It could be the cam may be ground at the wrong intake centerline, or LSA for lobe #7. A comparision with anothe lobe of the same function may the next move. You might become buddies' with the degree wheel.

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post #3 of 3 (permalink) Old Feb 9th, 08, 12:44 PM
Join Date: Aug 1998
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Re: what could cause this ???

Any chance that the cam was damaged before you even installed it ?? I would file the cam smooth, put a small pc of clay on the area that was hit, then put it back in the engine and turn it over by hand. Pull it back out and look at the clay to see if anything came close.

What part number cam is causing the problem ?

Either way, I would not re use the cam.

Bill Koustenis
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Waldorf Md
1971 Chevelle "Heavy Chevy" original owner

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