Not sure Ken B. and his IIRC nephew are still contemplating doing this but if so I ran across a set of unmachined Big Chief heads if they are interested in playing with them; http://www.ebay.com/itm/GM-10051129...603381?hash=item58f1212575:g:uBEAAOSwTM5YyFWj Would of posted in the original thread but it got locked up, anyway if someone wants to try and make those fit a BBB the price looks to be affordable. GL Derek
Gun drilling is a process used for drilling long straight holes. Typically a single flute drill with a through hole for pushing coolant or cutting oil through, to clear the chips. In a set of heads, there would be a couple holes through the length of the head, near the cumbustion chamber. There might be cross holes between the chambers that could be drilled conventionally, to tie the long holes together. https://en.m.wikipedia.org/wiki/Gun_drill
Thanks , Until i clicked it again for the second vid , it did not seem lickly the head would be spun on a stationary bit! So you would probably see freeze plugs on or plug on a gun drilled head. As far as race billet aluminum heads go anyways.
Just to be clear, I was never a part of the Big Chief project, I had already decided to start the Billet project which do have water ports for drag race strip only! I believe Jordan gave up on the idea for Buick motors although I have seen some Big heads in the shop.
Hey Ken, yeah that's it, its been a while I couldn't remember if you were involved or not but do I get points for remembering your nephew? Let Jordan know there are a set of blank Big Chief heads that aren't horribly expensive if he is interested in doing that on his own. Nice work on your billet heads by the way, thems some sweet looking eye candy, can't wait to hear the dyno results! I figured they would have some sort of cooling even for the strip but probably not very good for the street I would imagine. But I suppose going a quarter mile at a time what you did will probably be more than enough especially if the engine will be running alcohol/nitro mix? Derek
You are correct. The video was posted just to show a good example of a gun drill. In this case the work is spinning and not the bit. On a cyl head, the bit would be spinning. I've seen gun drilling machines that are built for doing rifled barrels, and both the work and the bit spin in opposite directions. I've heard it's for drilling a straighter hole because it keeps the bit from wandering, but I have a hard time wrapping my head around that.
I'm not the best at discussing some machining operations, but it's common to see in CNC production turning a bell mouthed hole that gets tighter as it gets deeper when the tool is located off center on the turret, or after a crash. It acts like a boring bar at first, until it pulls it towards center. If it pulls it towards center Many parts turned don't show it up except as tool life or breakage because long drills are mostly used for roughing and a finish tool cleans up afterwards (except in the case of a legit gun drilling operation where that tool is a finish tool with surface finish requirements) Spinning the drill bit also helps it find it's center if it isn't perfectly located for it's entire length. (ever indicate a gun drill at each end just for the fun of it...if you even can?) Not that this type of accuracy is needed to drill a deep hole in an aluminum head to connect water passages...
These would be easy peasy for a gun drill too. A machine shop I worked at for years used to farm stuff we couldn't do out to faxon machine (who also not so long ago got into the rifle barrel game incidentally). Anyway, I've been in there a few times and you wouldn't believe how deep those guys can drill. Side note: When I saw the title of this thread, I honestly thought you meant Justin Shearer ("big chief" from street outlaws TV show) was building a tomahawk or something! Haha (yes, that show is my guilty pleasure TV show....)