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Old 01-13-2020, 07:48 PM
joes455 joes455 is offline
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Default Piston skirt

Pics of skirt scuffing ,what are your thoughts?

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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119

Last edited by joes455; 03-05-2024 at 10:46 PM.
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Old 01-13-2020, 08:02 PM
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What stroke. How Much use?

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Old 01-13-2020, 08:32 PM
joes455 joes455 is offline
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All pistons are almost exactly the same .4.21 stroke not much use less than 500 miles,cylinder has same mirror image mark at very bottom center.the horizontal line is the bottom of cylinder edge at full stroke.Had what sounded like a rod knock with very little throttle.rods looked good.thinking bore to tight at bottom Its a hard block

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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119
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Old 01-13-2020, 08:46 PM
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Mine were way worse, but with a 4.75 crank.

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Old 01-13-2020, 08:49 PM
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Was bottom of bore properly deburred at original assembly? Have you measured or just assumed tight bottom?

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Old 01-13-2020, 09:05 PM
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Our nitro engine had severe scuffing like your picture; only worse. We solved that with extra piston to wall clearance. The pistons have less mass in the up-and/down direction than they do sideways across the pin bosses. So when the pistons are getting heated, they ovalize from unequal temperatures and get tighter at inboard and outboard edges.

Eric

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Old 01-13-2020, 09:12 PM
joes455 joes455 is offline
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More pics

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Old 01-13-2020, 09:17 PM
joes455 joes455 is offline
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Here u go

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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119

Last edited by joes455; 03-05-2024 at 10:46 PM.
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Old 01-13-2020, 09:22 PM
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Bottoms are debured.measure .0005 to .001. On the tight side I got to recheck specs

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Old 01-14-2020, 12:47 AM
Dragncar Dragncar is offline
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Quote:
Originally Posted by joes455 View Post
Pics of skirt scuffing ,what are your thoughts?
On a hard block engine you must run .002 more piston to wall clearance and .002 more ring end gap. Dan told me it is right there in the piston instructions. The engine I am doing right now has .006 clearance vs .004 if not hard blocked.. You will hear the pistons until the engine is warm.
Don,t do the extra ring gap and you might have a real problem.

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Old 01-14-2020, 01:32 PM
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What piston material and what skirt clearance?

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Old 01-14-2020, 05:27 PM
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Checked clearance and bottom of cylinder is too tight adjacent to the scrub marks on the cylinder .0045 I need .006 top of bore is .005 so how can I get what is required

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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119
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Old 01-14-2020, 05:29 PM
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I have a rigid hone with the required stones but don't want barreling

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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119
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