Re: That's gotta slow you down a bit
[Re: rebel]
#2366339
09/06/17 12:30 PM
09/06/17 12:30 PM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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I'd bet some sort of harmonics issue.
It could have also been a bad core but that stuff usually shows up before that much time goes by.
Seems to me the radial cracks looks like a harmonic issue though.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: That's gotta slow you down a bit
[Re: twayne24365]
#2366380
09/06/17 01:37 PM
09/06/17 01:37 PM
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Joined: Jan 2004
Posts: 4,580 Motor City
6PKRTSE
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I had one break like that from a #4 cam bearing spinning and breaking at that journal. The rear two cylinders were not opening or closing. Drove it all the way home like that. Still ran like a V6 just fine with slightly less oil pressure. It required full rebuild anyway.
1963 Belvedere 440 Max Wedge Tribute 1970 Charger R/T S.E. 440 Six Pack 1970 Challenger R/T, 528 Hemi 1970 Charger 500 S.E. 440 4 BBL 1970 Plymouth Road Runner 383 1974 Chrysler New Yorker 440 1996 2500 RAM 488 V-10 4X4 2004 3500 Dually Cummins 4x4 2012 Challenger R/T Classic.
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Re: That's gotta slow you down a bit
[Re: rebel]
#2366383
09/06/17 01:43 PM
09/06/17 01:43 PM
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Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
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Really strange looking pattern on the 2nd lobe down from the break.
Never saw one look like that before....... But I have to suspect its related.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: That's gotta slow you down a bit
[Re: madscientist]
#2366722
09/07/17 12:12 AM
09/07/17 12:12 AM
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Joined: Jan 2003
Posts: 4,287 Morrow, OH
markz528
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I'd bet some sort of harmonics issue.
It could have also been a bad core but that stuff usually shows up before that much time goes by.
Seems to me the radial cracks looks like a harmonic issue though. Years ago my buddy would break cams on a regular basis in a high hp chevy small block. It was a harmonics issue - he was using a gear drive. A Jesel belt drive solved the problem.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: That's gotta slow you down a bit
[Re: rebel]
#2366738
09/07/17 12:44 AM
09/07/17 12:44 AM
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Joined: Mar 2011
Posts: 3,090 Michigan
A727Tflite
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What condition are the #1, 2 and 3 cam bearings? Have you measured them against the cam journal diameters?
Last edited by Transman; 09/07/17 12:46 AM.
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Re: That's gotta slow you down a bit
[Re: markz528]
#2366796
09/07/17 03:27 AM
09/07/17 03:27 AM
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Joined: Dec 2006
Posts: 4,647 aotearoa
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I'd bet some sort of harmonics issue.
It could have also been a bad core but that stuff usually shows up before that much time goes by.
Seems to me the radial cracks looks like a harmonic issue though. Years ago my buddy would break cams on a regular basis in a high hp chevy small block. It was a harmonics issue - he was using a gear drive. A Jesel belt drive solved the problem. I'm already running a belt drive.
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Re: That's gotta slow you down a bit
[Re: A727Tflite]
#2366831
09/07/17 09:29 AM
09/07/17 09:29 AM
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Joined: Dec 2006
Posts: 4,647 aotearoa
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What condition are the #1, 2 and 3 cam bearings? Have you measured them against the cam journal diameters? Cam bearings all good. None have moved
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Re: That's gotta slow you down a bit
[Re: fast68plymouth]
#2367235
09/07/17 11:16 PM
09/07/17 11:16 PM
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Joined: Jan 2004
Posts: 13,247 Mt. Vernon, Ohio
dartman366
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Really strange looking pattern on the 2nd lobe down from the break.
Never saw one look like that before....... But I have to suspect its related. that was the first thing I noticed, looks like a flat spot or somthing at the begnning of the ramp, looks like the same thing on the lobe nearest the dist drive gear, looks much lighter like a ghost mark.
Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.
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Re: That's gotta slow you down a bit
[Re: rebel]
#2367554
09/08/17 06:02 PM
09/08/17 06:02 PM
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Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
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I would see if you could find an 8620 cam core for the replacement, and verify with the cam grinder you absolutely have enough spring load to keep the valvetrain under control.
I would also be trying to figure out what caused that witness mark on the lobe.
I don't know what your combo is, but it's the kind of mark I'd expect to see if there was some minimal contact between an aluminum rod and the cam.
Since you have an aluminum block its also certainly possible that just before/after the cam actually let go it whipped around inside the cam tunnel, and that's just the mark that was left. If so, there should be a corrosponding mark in the tunnel where the contact was made.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: That's gotta slow you down a bit
[Re: fast68plymouth]
#2367564
09/08/17 06:38 PM
09/08/17 06:38 PM
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Joined: Oct 2011
Posts: 3,036 bean town ....Ca
WHITEDART
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bean town ....Ca
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Is it me or has it been repaired...did you check it for straight before the in stall
In the 8s N/A.with Brett miller W8's 5.07 at 133 at 2700lb
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Re: That's gotta slow you down a bit
[Re: markz528]
#2367668
09/08/17 11:22 PM
09/08/17 11:22 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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I'd bet some sort of harmonics issue.
It could have also been a bad core but that stuff usually shows up before that much time goes by.
Seems to me the radial cracks looks like a harmonic issue though. Years ago my buddy would break cams on a regular basis in a high hp chevy small block. It was a harmonics issue - he was using a gear drive. A Jesel belt drive solved the problem. I've been using a gear drive for the last 8 years with no problems and I'm putting engine together now with one
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