I'm curious to hear from folks that have enlarged their right main oil galley to 1/2" all the way to the back of the block (the last 10.5"). In the past I have drilled from the rear of the blocks using a 12"x 1/2" two flute drill bit to enlarge the galley from 7/16" to 1/2". I never really was comfortable with that process because when the two diameters finally meet, they are usually not inline. I know it's not desirable to enlarge the lifter feed openings. It's also interesting when the drill bit breaks into the lifter feed openings and happens to grab, ... wanting to break your wrist. Drilling slow and easy usually helps. I looked into buying an extra long 24"x 1/2" drill bit to come in from the front, as to use the existing 11-1/2 inches of 1/2" galley as a centering guide. Another interesting note I found out is the galley is actually larger than 1/2". I used a hole gauge and found it to be roughly .525, though that may vary from block to block and depending on tooling used. I have been looking into a 1/2" 3-flute drill bit that has a fairly long 7/16" pilot to keep things inline. The problem there is that the whole bit would still have to be extra long or it would need to be extended. It also seems like there is too much material to remove for a reamer to do the job. Any input from folks that have done this with good straight success would be appreciated. Larry
Regarding breaking through, we usually slow the feed at the intersection if there's any breakage risk. Copied for perusal... [Another sure way to overload a cutting tooth is to increase the feed rate drastically beyond its structural or chip-disposal capacity. Machine structural deflection accomplishes this is the example of a drill breaking as it breaks through the work. As the heavy thrust of the chisel edge is relieved, structural members spring back toward their unstressed shape, and the drill lips plunge into the work for an oversize bite. Feed mechanisms may employ air or hydraulic fluid whose compression is elastic; or gearing and a leadscrew nut fit may introduce backlash. Machine way motion becomes jumpy at slow speeds (“slip-stick” motion), even when heavy lubrication. A milling cutter at slow feed may actually rub until pressure builds up. It then may dig into the work and surge ahead. Adding to the difficulty, the sudden change in cutting torque adds to the pounding caused be teeth entering the cut. Torsional vibration and backlash tend to develop in a rotary drive train. Should cutter rotation become so erratic that it momentarily stops, carbide teeth will generally break at once by being bumped into the work. With some teeth gone, the entire cutter may fail progressively as each successive tooth is unable to carry the extra load left by the preceding damaged teeth.] The same issues are dealt with in a machine as by hand. Drill bits are kind of grabby as ground, so it helps to remove some of that, like when cutting brass. Whether boring or facing, it was necessary to remove or stagger some of the teeth in the cut. You might be better off with a reamer, and that's how I've done some blocks. Ignore the enlargement recommendations, the typical .010-.012" is more for holding accurate size and roundness. Feed it heavy. I don't buy long tools on my dime. Half-lap and braze the shanks, and/or charge the tool costs to the customer. The 3 flute bit sounds interesting. Curious if the lip is thicker and flutes short in the ones you are looking at. There can be too much springy-ness in longer flute tools and I've seen a lot more broken 3 flute drills than other types when tool reps start playing around with your stuff.
I've had better results using a reamer, made an extension for it to go all the way thru. You are right they normally don't meet evenly. Just go slow until it breaks thru in the middle. Once opened we ran a tube thru the whole galley to reduce oil flow to the lifters and to the top end. The problem I won't do it again is, you then have to make step tools to open up the lifter bore back up for the lifter to fit. Pushing back the tube and denting it for clearance. (an old Mopar trick the small block racers did) Once that is completed you can drill a small hole to feed the lifter. The hole is already too big from factory and now after the drilling of the galley it is huge, forget the size of the top of my head. The concept works extremely well to keep oil in the bottom end but an absolute pain in the butt. Don't expect work like this to be done in a hurry! Friends would ask me "you still building that Buick" mean while they are burning up bearings and mine keeps going.
Cool, ... will do. That's actually why I called you last night. Thanks Steve. Wow guys, ...... that's a lot of great technical information! Thank You Larry
Wouldn't it be easier to restrict the oil outlet of the lifter, than to restrict the oil inlet TO the lifter? The lifter should already have a metering valve inside. Shouldn't matter how big the oil supply hole to the lifter is, the metering valve controls how much goes up the pushrods. And if you can't restrict it there, restricted pushrods are available. The downside to all this is that the valve springs need a lot of oil flow to cool them. Some racers build valve covers with oil-spray nozzles specifically to cool the valve springs. Of course, lower rpm and less-stiff springs don't need as much cooling as the high-rpm stuff.
tried this years ago and stopped. In our case with unshrouded lifters it caused hemorrhaging from lifters front to back on that side. that's when we stopped and went to balance tube front to back to get away from Losing #7 bearing. This was to keep it together regularly turning 7000 rpm. with std block prep and TA or modified front cover most of this is not required have several 600 - 650 hp motors that live fine without all that . I don't think there is any situation I would do this mod again.
