 spark plug gap closed on two plugs, what causes this? |
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| siverson |
 Jun 13 2016, 09:23 PM
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#1
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Advanced Member  Group: Benefactors Posts: 2,451 Joined: 5-May 03 From: San Diego, CA Member No.: 654 Region Association: Southern California 
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hi - quick question from the garage. cdi box died on my six. got replacement and car starts right up (good). but runs like crapola right away. pulled the plugs and on two the electrode (term?) is no touching the plug.
is this why my cdi boxed died? or is this a result of it dying? or? plugs were 1k miles old. cdi box was 46 years old. |
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| brant |
Jun 14 2016, 09:24 AM
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#2
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914 Wizard Group: Members Posts: 11,824 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains 
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on a -6 with high compression and high lift cams the tolerances are very close
a missed shift or too much rpm causes things to kiss "hopefully softly" I've broken a rocker before from a missed shift... I've even kissed a valve softly enough not to hurt the rocker, but enough to loosen the adjustment lock nut... I've seen valves bend slightly... enough to have to be replaced... others have done much worse... not sure if its valve float? but an over rev allows things to touch with all of the inertia at high rpm.... but it can happen (I run 9k valve train for this reason) valves can touch plugs can touch and much worse also. |
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| r_towle |
Jun 14 2016, 01:08 PM
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#3
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Custom Member Group: Members Posts: 24,661 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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QUOTE(brant @ Jun 14 2016, 11:24 AM)  on a -6 with high compression and high lift cams the tolerances are very close a missed shift or too much rpm causes things to kiss "hopefully softly" I've broken a rocker before from a missed shift... I've even kissed a valve softly enough not to hurt the rocker, but enough to loosen the adjustment lock nut... I've seen valves bend slightly... enough to have to be replaced... others have done much worse... not sure if its valve float? but an over rev allows things to touch with all of the inertia at high rpm.... but it can happen (I run 9k valve train for this reason) valves can touch plugs can touch and much worse also. Hitting valves, no question. An over revving situation making a piston hit a plug....I can't see it unless it flexes the crank, or stretches the rod.... Carbon build up...that makes sense. |
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Posts in this topic
siverson spark plug gap closed on two plugs Jun 13 2016, 09:23 PM
siverson 914 Jun 13 2016, 09:24 PM siverson 914 Jun 13 2016, 09:25 PM stugray Cyl touching? (Does it have High CR pistons? does ... Jun 13 2016, 09:40 PM nine9three The only thing I know that would cause this would ... Jun 13 2016, 09:42 PM veekry9 (Pelican Pix)
They can look as bad as this before... Jun 13 2016, 10:34 PM
nine9three
Carbon buildup on the pistons are usually the cu... Jun 14 2016, 10:12 AM brant You missed a shift or most likely over revved it o... Jun 13 2016, 11:07 PM r_towle I'm very unclear on how a mis shift or over re... Jun 14 2016, 09:00 AM Luke M I would check to make sure those are the proper pl... Jun 14 2016, 09:33 AM Frankvw Mmmmm interesting topic.
but to be honest...I am r... Jun 14 2016, 10:36 AM brant
Mmmmm interesting topic.
but to be honest...I am ... Jun 14 2016, 10:40 AM siverson Interesting, thanks for the feedback.
I don't... Jun 14 2016, 12:16 PM brant
Interesting, thanks for the feedback.
I don... Jun 14 2016, 12:24 PM siverson New plugs.
-Steve Jun 14 2016, 12:18 PM siverson In there now.
-Steve Jun 14 2016, 12:19 PM stugray Engine parts DO flex.
The greatest stress in an en... Jun 14 2016, 01:04 PM |
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