My home inspection of Speedmaster heads

12many said

The SM hole is drilled into the chamber and threaded. A straight threaded hole into chamber. The TF’s take the additional step of tapering or flaring it out to the chamber surface like I said to about a 20mm x 16mm oval, radiused.

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I don't think anybody's disagreeing that you get what you pay for those trick flows are nice and have all the extra options built into them.. as they should for the money.. just like the sm's are budget-minded and the extras aren't done and allow the do-it-yourself guy to take care of that with no extra cost out of pocket...