Project V8 M3: Tapping Our Block

Jan 9, 2017 update to the BMW M3 project car

Crud like this gets in the way of proper torque readings, and can ruin an engine.
It's the details that can separate a good engine from a bad one. We cleaned our block's holes with a clean out tap.
ARP makes more than just bolts–their catalog has tools, too.

There are glamorous parts of engine building. Then there’s the rest. Once we’d torn down our engine and measured what we had, it was time to start preparing it for its next life as the heart of our BMW M3 track car.

It’s not fun to fix a stripped bolt hole once the engine is in the car, so now was the time to fix any broken, stripped, or dirty bolt holes, as well as give the block a thorough examination for other issues. Fortunately, our engine was fine, and didn’t need any repairs or bolts extracted. However, it did need to have its threads cleaned.

Can’t you just bolt everything into dirty threads? Sure, it will work for your exhaust hanger, but old sealants, grease, dirt, and buggered up threads can seriously harm an engine build. These factors conspire to give false torque readings, meaning torque specs can be reached before the bolt is actually tight. In extreme cases, you could even crack the block by tightening a bolt down into a hole full of crud.

How do you clean the threads in an engine block? Good question. Fortunately, there’s an easy answer: A clean out tap. This tool looks similar to a normal thread tap, but is designed to clean existing threads rather than cut fresh ones. We ordered ours from Automotive Racing Products, and chased every one of our block’s holes.

Was this the most exciting task (or update) we’ve completed? No, probably not–but at this point, we’re building a solid foundation for awesome stuff in the future. Awesome stuff like a terrifying E36-chassis BMW M3 that kills tires like a honey badger. Stay tuned.

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