[T3] cranks and clearances

[Mike Fisher]

Jim says pressure doesn’t matter only oil flow.

On Fri, Aug 14, 2020 at 6:00 PM Keith Park <topnotch at nycap.rr.com> wrote:

> Ok, Im getting Cranky!
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> The crank that was in my 2056 was a 10 under, thats fine, but for some
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> reason despite my measuring .003 to .0035 main bearing clearances, it
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> started
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> to sieze when it got warmed up with the break in oil in there, what is
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> additionally interesting is that the sacrificial bearing shells didnt do
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> their work very well,
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> you can run your fingernail across the journals and feel some light
> scoring.
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> The crank for this build is my spare, its seen alot of use and despite
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> having 2 rod journals shells well into the copper the machine shop found it
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> in the middle of the
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> spec and just polished it, and it does, and did look good, except... the
> new
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> bearing shells on it are a bit loose.
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> These are old stock Repco bearings, and im finding between .0045 for the
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> split one to .005 for 1 and 3.  Now im measuring this with a mic and bore
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> gauge, using the mic's
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> measurement for journal size as the 0 point for the bore gauge, so it
> should
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> be accurate.  Bearings all torqued into the case.
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> SO...
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> im kinda porked... the wear limit is .006 or so, so I should be around .002
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> or 3, and the bearings are what the bearings are, the crank SHOULD be in
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> spec, if the shop measured it properly
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> and since they have better equipment that I do....
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> Should I have it taken down 10?  well.. they say its in spec NOW... and 10
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> under didnt do wonders for the hardness layer on the last crank and since
> 2L
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> Porsche cranks dont grow on trees... risk it
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> or run the .005 with the stock journals and stock hardness layer intact?
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> after the incident with the break in oil im inclined to keep things on the
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> loose side of ideal but past builds have had
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> oil pressure issues so its sensitive to that, although the previous build
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> had NO pressure issues.
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> What to do?  What are people finding the main bearing clearances to be out
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> there in stock size land?  they  are sending me a set of silverlines to
> try,
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> but they arent the quality of the Repco's.
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> Keith
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> Topnotch Restorations
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> topnotch at nycap.rr.com
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> http://www.topnotchresto.com
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> 71 Squareback  "Hothe"
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> 65 Notchback  "El Baja Rojo"
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> 93 RX7  "Redstur"
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> 13 Subaru Outback "Blendin"
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