Camshaft differences
March 31st, 2023, 05:54 AM
#1
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Camshaft differences
the camshaft on the left is the original out of my 1976 455 4bbl the camshaft on the right is the original from a 1970 350 2 bbl motor . They share the same stamping but the fronts differ . If I’m reading it right the olds faq page say they should be different with the 455 cam having slightly more lift. Is this a case of using the same cam for both motors ? And why the difference on the front of these ? I was going to try the 455 cam in the 350 but I see no point in it now .
March 31st, 2023, 07:14 AM
#2
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The notches on the front just identify the cam blank used to grind that particular cam. Olds used paint stripes to identify the actual cam specs and application. By 1976 there were far fewer different cam profiles used, and frankly all the high lift/high overlap cams were long gone, so far fewer different cams were needed. The 1970 350 2bbl cam should be P/N 400084, with 250/264 duration, 36 deg overlap, and 0.400/0.400 lift. Pretty mild. the 1976 455 cam should be P/N 400117 with 258/272 duration, 44 deg overlap, and 0.435/0.435 lift.
March 31st, 2023, 09:40 AM
#3
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The notches on the front just identify the cam blank used to grind that particular cam. Olds used paint stripes to identify the actual cam specs and application. By 1976 there were far fewer different cam profiles used, and frankly all the high lift/high overlap cams were long gone, so far fewer different cams were needed. The 1970 350 2bbl cam should be P/N 400084, with 250/264 duration, 36 deg overlap, and 0.400/0.400 lift. Pretty mild. the 1976 455 cam should be P/N 400117 with 258/272 duration, 44 deg overlap, and 0.435/0.435 lift.
March 31st, 2023, 09:51 AM
#4
Old(s) Fart
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Yes, 401348 is just the casting number for the blank, not the finished cam. Checking lift can be done with V-blocks and a dial indicator, but that will give you lobe lift. The published numbers are valve lift after the 1.6:1 rocker arm ratio. Divide the published numbers by 1.6 to get the lobe lift. Unfortunately, measuring actual lobe events (duration, opening and closing) really requires the cam to be installed in a block or equivalent fixture.
March 31st, 2023, 11:22 AM
#6
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Yes, 401348 is just the casting number for the blank, not the finished cam. Checking lift can be done with V-blocks and a dial indicator, but that will give you lobe lift. The published numbers are valve lift after the 1.6:1 rocker arm ratio. Divide the published numbers by 1.6 to get the lobe lift. Unfortunately, measuring actual lobe events (duration, opening and closing) really requires the cam to be installed in a block or equivalent fixture.
March 31st, 2023, 11:27 AM
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April 1st, 2023, 06:32 AM
#10
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I did some measuring as instructed and found out pretty much what we knew . The 455 cam has a little more lift than the 350 cam . The interesting thing I found was camshaft runout . The 455 cam had nearly .007 runout on the Middle journal compared to the 350 with .0025. So it seems I’m not messing with the 455 cam . I do thank you I’ve learned some more valuable info 👍
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