Block core plugs

Crank, rods, sealing, pistons, block, flywheel etc
Guy Croft
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Joined: June 18th, 2006, 9:31 am
Location: Bedford, UK

Block core plugs

Post by Guy Croft » July 22nd, 2006, 4:30 pm

What are they for? To stop the block cracking if it freezes in winter? No.
Some functional purpose? Not really.
Core plugs are just a necessary feature of casting, without them you can't make some parts.

They should always be replaced on overhaul, because although they might look fine on the outside, they can be seriously corroded on the inside due to neglect of coolant & additive, in some cases wafer thin or just about to develop 'pin-inappropriate' holes.

Some firms use fabulous bolting systems to hold the core plugs in place, never quite understood the need, the plug should stay in merely as an 'interference fit', unless it is the wrong size for the bore. Must be some kind of high pressure cooling system to push out a core plug...
Core plugs and tools.JPG
Tools for knocking plugs into place - hammer and drift. If you don't have the exact tool you can make one or use a big socket...
Core plugs and tools.JPG (164.86 KiB) Viewed 11555 times
Core plugs & sealant.JPG
A little silicon sealant around the bore is a good idea, make sure the bore is thoroughly cleaned with fine abrasive paper.
Core plugs & sealant.JPG (172.07 KiB) Viewed 11555 times
Core plug fitting.JPG
Core plug fitted, make sure it is fully fitted in the parallel section, often there is a chamfer on the outer edge, and not tilted over - it may leak.
Core plug fitting.JPG (169.03 KiB) Viewed 11549 times


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