| Flat Tappets Flatening Cams [message #118439] |
Fri, 11 March 2011 13:19  |
g.winger
Messages: 792
Registered: February 2008
Location: Warrenton,Missouri
Karma: 0
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This is comparing apples and oranges,,,,but. May Carcraft mag has an article on tha SBC 400. On page 28 they show a foto and text on how they ground down a new cam in 25 min. That being carefull with time tested breakin procedures. They used 130-340 (closed-open) springs and blame the "to much spring pressure" as the cause. Of course we don't use that much spring,,,,but I thought it intresting that even CC can grind down a cam that fast.,,,,,PL (What I meant by apples/oranges is we don't run that much spring)
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| Re: [GMCnet] Flat Tappets Flatening Cams [message #118442 is a reply to message #118439] |
Fri, 11 March 2011 13:45  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Paul, many things affect cam wear besides spring loading. Mismatch of
materials probably is the guilty party for accelerrated or premature cam and
tappet wear during break in more often than not. Long slot high ratio rocker
arms like the SBC uses to get more valve opening without taller camshaft
base circles is another. Incorrect pushrod length also figures in there
along with possible coil bind on the springs. It is a vast book with many of
the pages blank. Also, hot rodders, of which myself is included, are
notorious for reving the snot out of newly assembled engines. 1500--2000 RPM
for cam & lifters for the first 20 minutes is kinda the industry standard
recommendation. If you give the engine a sudden blip of throttle, without
load it can easily bounce up to 5000 in a second or two and that is enough
to cause the new surfaces to gall & microweld to each other. That starts the
slide down the slippery slope to cam destruction in spite of the best cam
lubes and proper clearances. Hard to resist hearing those SBC engines sing
that song and many of us can not resist that temptation. Kinda like that
good looking redhead in the short shorts leaning on the fender of that tri
five chevy. Pretty hard to ignore that.<Grin>
Jim Hupy
Salem, Or
78 GMC Royale 403
On Fri, Mar 11, 2011 at 11:19 AM, Paul Leavitt <leavittpaul@yahoo.com>wrote:
>
>
> This is comparing apples and oranges,,,,but. May Carcraft mag has an
> article on tha SBC 400. On page 28 they show a foto and text on how they
> ground down a new cam in 25 min. That being carefull with time tested
> breakin procedures. They used 130-340 (closed-open) springs and blame the
> "to much spring pressure" as the cause. Of course we don't use that much
> spring,,,,but I thought it intresting that even CC can grind down a cam that
> fast.,,,,,PL (What I meant by apples/oranges is we don't run that much
> spring)
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> GMCnet mailing list
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