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Classic Austin Mini Cooper-850 / 948 / 998 CENTER MAIN STRAP

Classic Austin Mini Cooper-850 / 948 / 998 CENTER MAIN STRAP

Classic Austin Mini Cooper-850 / 948 / 998 CENTER MAIN STRAP
Qty:
$14.95
Part No: CMS10
Internet Price $14.95
Steel center main strap for small bore engines, comes with longer high tensile bolts. Main top cap needs machining flat, no other modifications required. On all performance A series engines it is essential to ensure accurate and as near permanent location of the center main bearing of the crankshaft as possible. Flexure allowed here, especially at sustained high RPM levels, can cause spun bearings, crank or main cap breakage with severe or mortal damage to the engine.

This strap is used to give support and strengthen the centre main bearing cap on small-bore engines (850/998/1098cc). It helps counter the problems caused at higher rpm where crankshaft flex (‘whip’) causes the standard cap to move (‘shuffle’) leading to bearing failure and possible breakage of the main bearing caps. In particular, where higher rpm than standard will be the norm – i.e. in excess of 6,000rpm. Especially where this is for extended periods.

The standard centre main cap needs to be machined by a competent engineer or engineering shop, as the finished surface needs to be absolutely flat. The final finish being ground where practical.

The cap should be milled straight across along a central axis from one retaining bolt-hole to the other using a 1.03125”(1 1/32”) or 26mm cutter with as small a corner radius as possible, down to the original bolt head flat surfaces. This is necessary, as just milling the cap completely flat will remove the centre thrust washer locating slots.

Once machined, check the strap for fit to the cap, increasing the edge chamfers as necessary to clear the corner radius left.

When finally assembling the engine, ensure strap is fitted with adjusted chamfer edges to cap, fit new bolts supplied and torque down to standard setting (threads clean and dry, 65lb ft.). Higher torque settings are not necessary.

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Related Technical Articles:
Classic Mini Cooper Hi Performance engine parts & Sumpguards -33
Created: January 15, 2019
Built-Up short blocks for the Classic Mini make maintenance and/ot upgrades very easy. Or factory original design connecting rods and competition 4-bolt center main straps for the crankshaft are just a few of the options from the leaders in Classic Mini parts.
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