Search for a piloted drill bit

Discussion in 'Small Block Tech' started by jon-p, Sep 7, 2017.

  1. jon-p

    jon-p Little olds

    Looks like it may be time to enlarge that 7/16 in. diameter oil feed passage leading to the oil pump. Have not located this tool. I've seen this mentioned on these forums but hours on the web has netted zilch. Need at least 1/2 inch bit with a 7/16" diameter pilot.
  2. badbuik

    badbuik Well-Known Member

    Just because you want it, doesn't mean it's out there... For a piloted bit ya might wanna try searching aircraft tooling website...Maybe Grainger or Fastenal too...
    Gary G
  3. alec296

    alec296 i need another buick

    TA performance has long aircraft bits for this. They are not piloted. You may want a drill press if your not sure about drilling it. I have done this a few times with regular drill. If you have to open hole some with a middle size bit .
  4. Richie

    Richie Well-Known Member

    Can you use an end mill (counterbore tool) with a pilot diameter? Union Butterfield makes a 1/2 diameter with a changeable pilot diameter. Either number 6210039 or 6210009 accepts a 7/16 pilot. I am also sure you can find others that make similar tools.

    from the Union Butterfield catalog:

    Counterbore Body - Interchangeable Pilot Type

    Short set
    Long set
    Used to enlarge the end of a preformed hole
    when a flat bottom is required. The counterbore
    is an end cutting tool which utilizes and
    interchangeable pilot to align the enlarged hole
    being machined with the preformed hole. The
    3 and 5 flute counterbore reduces chatter and
    improves finish.


    300sbb_overkill likes this.
  5. Short_Crank

    Short_Crank Platinum Level Contributor

    Purchase a 1/2" drill and send it to any tool and cutter grinding shop. They can grind the tip down for you and maintain a cutting edge on the transition to 1/2".

    The piloted counterbore idea would probably work but those generally need more tool pressure than a drill.
    8ad-f85 and 300sbb_overkill like this.
  6. jon-p

    jon-p Little olds

    Thanks, found local shop that does this.
  7. alec296

    alec296 i need another buick

    You will have to be careful you don't go too far and break out at the 90 turn. And round the 90 turn with a long die grinding tip
  8. Short_Crank

    Short_Crank Platinum Level Contributor

    Great. Let us know how it works out.
  9. 8ad-f85

    8ad-f85 Well-Known Member

    A drill press wouldn't stop a long bit from walking.
    You could set up a drill guide bushing or jig, but that would only help for a little bit of depth.
    Short pecks, clear the chips periodically, and an accurately sharpened tip helps.
    One thing you might notice is that factory blocks in general are often drilled from both sides and meet in the middle.
    I can't recall/don't want to look if some of the Buick's galleys are this way too but you might want to visually look, and if there's a huge mismatch to make a decision on your strategy anytime you are drilling a hole done that way.
  10. Mart

    Mart '71 350 GS, almost stock

    You can also grind a combo point (59* & 45*) on drill tip.
    The 45* will not walk as much as the 59. Acts more like a reamer edge.
  11. Jim Blackwood

    Jim Blackwood Well-Known Member

    Why are you drilling it to 1/2"? Even Buick eventually went to a 5/8" passage in the later V6 didn't they, along with a pickup tube to match? I could maybe understand it if you don't use a piloted bit but with one the risk of breaking out is minimal even at 5/8". If you are conservative go with 9/16". That's enough of a difference to make it worthwhile.

    You need a 12" long drill bit. My local hardware store carries those. Not terribly expensive either. To grind the pilot you can chuck it up in your hand drill, spin it and apply it to the wheel of a bench grinder, or use an angle grinder, or just grind it by hand. It doesn't have to be perfect but the sloppier you make it the more it will tend to cut oversize and you might want to take that into account. You can shape the cutting edges by hand, there is no real magic here, just give it a little angle so it will cut. If you are careful you can do the whole job freehand on the bench grinder and it just isn't that hard to do. The most important part is to try and get the pilot centered, in other words grind the same amount off both sides. It doesn't have to be perfect. If it isn't round, so what? All it has to do is keep the bit centered in the existing hole. If you get it off-center it will just tend to cut oversize and you can check it on a piece of scrap before drilling your block. You guys are making this way too complicated.

    8ad-f85 likes this.
  12. alec296

    alec296 i need another buick

    9/16 on a 350 block makes the wall thin. You need to sonic test if your going that large. The hole would need to be drilled offset toward outside of block.
  13. Jim Blackwood

    Jim Blackwood Well-Known Member

    Really? I went 9/16" on my 340 and there was room to go 5/8". I'd have thought the 350s were the same.

  14. jon-p

    jon-p Little olds

    My initial step was to drill to a .500 dia. to 10 1/2" depth; that is done.. A retired machinist advises reaming the passage to the desired .532 to produce a fairly smooth wall finish.
    .532" diameter gives a 50% increase in cross sectional area over the 7/16 factory hole. Why only .532, frankly, I have become very conservative regarding this aluminum motor and down right gun shy about accidentally creating any more problems. This not my first motor rebuild , but it is the only one to suffer low oil pressure. I am boring this oil passage in an attempt to achieve some reasonable oil pressure. This low oil pressure problem is not uncommon on rebuilt aluminum V8's. TA's tech told me that they are currently working with another client with an aluminum motor, built by a well known shop, that has 10 psi oil pressure at idle and 20 psi revved up. TA is shipping a V6 pickup and a later oil pump cover.
    This motor originally had lifters that did NOT flow oil at the push rod cup. I am using lifters with an oil feed orfice because the non-oiling type are unavailable from USA produces . In a "one size fits all"money saving move Lifter makers dropped the hole less version for the rocker oil feeding version. I am using Crower lifters supplied by Johnson lifters. Johnson's website states that the lifter oil flow is metered to prevent a loss of oil pressure, a recognized cause of oil pressure loss. Removing the intake and valley cover and using an electric drill to run the oil pump, I see that excessive amounts of oil roll out of the cup orifices of some lifters, others pass somewhat less. Very inconsistent. The only way to eliminate this as a factor is to plug the lifter tops and see if the pressure improves.
  15. 8ad-f85

    8ad-f85 Well-Known Member

    Any way to swap the lifter cups or otherwise restrict inside the lifters?
    When you say "the only way to..." it suggests to me that the tip of the iceberg is being just being approached.
    Are the lifters all at the same height when the varied flow is observed?
    Are there .875" ford lifters available with hole-less cups?
    It would be fairly simple to bore the block to the ford size to start with a tighter tolerance and have minimal effect on the cam's events if you are using a mild one.
    Obviously there are other ways to control the leakage to affect the sum.
  16. BuickV8$Mike

    BuickV8$Mike SD Buick Fan

    Reaming will produce a nice finish. Reamers are for removing very little material maybe 0.005" on the diameter max. however.
  17. 300sbb_overkill

    300sbb_overkill Well-Known Member

    If you're machine reaming there should be 1/64" to 1/32"(.015" to .030") of material left in the hole for it to clean up properly.

    The holes can be opened up with a hand reamer from .842" to .875", wouldn't be that hard at all to do with aluminum. A hand reamer would help keep the hole straight doing it by hand, a lot better than chucking a machine reamer in a hand drill!

    .875" - .842" = .033", that is only .0165" per side of material to be removed so not that much if you can find Ford lifters that would work? That is if that size lifter is combatable with the cam lobe?(not sure if the lobe has to be wider or not?)

    Try a parts wanted ad here for a set of lifters without the holes in the cup and see if the old cups will fit in the new lifters? Someone may even "sell" them to you for the cost of shipping?
    8ad-f85 likes this.
  18. jon-p

    jon-p Little olds

    "tip of the iceberg" is maybe true. This motor has only 500 mi on it since its rebuild, but maximum hot oil pressure is only 25 lbs with a high volume pump modification. I think this aluminum motor has an oiling system that is barely adequate considering that the suction side of the pump is fed by a passage only 7/16' diameter and 14 ' long with a 90 degree turn. But with a 90,000 mile motor with slightly looser lifter bores passing a little extra oil around the lifter body, oil passing lifters, a slightly loose oil pump gear shaft, and .0025" main bearing clearance (rods are.0015"), .004" oil pump gear side clearance(recommended .002-.003) and .003 end clearance there may be just too many places bleeding off the pressure. Built cast iron motors and NEVER had such problems. Aluminum heads are great for running high compression( this f85 has a true 10.6:1 and no detonation with 35 degrees total timing plus 14 degrees of vacuum) but this is my last aluminum block.
    Removing the lifter caps and silver soldering the hole shut has been suggested.
    The oil inlet passage is being increased to .532" diameter and a larger V6 pickup tube is coming from TA and a new oil pump cover which will be shimmed to .001.
    I could remove the after market gauges, go back to the factory idiot lights, and forget the whole thing.
    8ad-f85 likes this.
  19. Jim Blackwood

    Jim Blackwood Well-Known Member

    That main bearing clearance is your biggest problem.

  20. jon-p

    jon-p Little olds

    Crank regrind is the next step. Thanks for your advice.

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