[19Fordy]

This may seem a bit anal and long but, I think it's worth reading.

I may not be fully understanding the problem but, wouldn't it be best to mark the location of the holes with a transfer punch, remove the intake and line the inside of the "valley" with paper or rags or a plastic bag laid flat. Then cover that same cloth or a plastic bag with masking tape (sticky side up) and place a bunch of those of those little round super duper high strength magnets on top of the tape and under the drilling location so catch the chips.

Also, if possible, mganetize the HSS pilot drill,intermediate size drills and tap drill AND tap ADD add a dab of wheel bearing grease to each to help catch chips. When hand drilling cast iron I always go one drill below the drill shown on the tap drill chart to help compensate for minor drill movement while drilling. Practice a couple of times on a scrap piece of cast iron if you have any. Cast iron drills quite accurately if you have a pilot hole.

When all done, I would VERY carefully roll up the rags, plastic bag and tape used in the "valley" to capture all the chips and remove it. Then I would go back with a flashlight and a mirror and another very strong magnet glued to a non magnetic stick and meticulously cover every bit of surface area, including under the bottom edge of the drilled holes to make sure no chips or potential chips from the newly tapped holes remain.

QUESTIONS: Do you think the fellow who built you engine would be as careful as the above procedure. Does he have a better procedure? Is he willing to take all the time to patiently do this as he know this will VOID warranty, anyway.

I always worry when such an important mission is taken on by someone else, unless they have a better method. Assume you are searching for land mines that will blow up you new engine. I am sure you will be successful.