Varied Lifter Bore Oil Holes

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nm9stheham

nm9stheham

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I got to looking at a 340 block and a 360 block and saw some significant variations in the oil holes where the lifters intersect the oil galleries. The 360 was pretty consistent side-to-side, and was fairly close to the hole size on the passenger side of the 340. (1st pix is the smallest hole on the passenger side, 340 block.) But the 340's driver's side holes were a lot bigger. (2nd pix is the largest hole on the driver's side, 340 block.)

So any cause for concern or to do any mods? The lifters bores are tight as a tick... in fact, we had to ask Crane to replace 3 of the lifters that were up around .905" OD and would not readily slip in. So, I can't see that we will have any excess leakage out of any of the bores. And, the larger holes are on the driver's side, which is the lower pressure side. Plus, the smallest hole overlaps the oiling band in the lifter by about half the diameter of the oil hole when on the cam heel, so that SEEMS OK .

Any experienced comments appreciated.
 

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I wish I knew. This is a possible issue I've never thought about or been aware "could be"
 
Well, my thoughts continue to be that it is not really an issue. The hydraulic lifters should only take a little oil once they are pumped up, so if the oiling band on the side of the lifter is exposed to the hole into the gallery when on the heel of the cam lobe, then that ought to do it. The oiling band is not exposed to the gallery pressure when at any significant lift height; it just gets oil when down at the bottom.

And the good fortune in this situation is that the larger holes are on the lower pressure (driver's) side gallery. So at this point, we'll proceed as is.

But as said, if anyone knows of an issue associated with this irregularity, I'd sure like to hear it. I couldn't see anything specific on the 'oiling mods' threads on this, and the 'tube and peen' mod is not meant for hydraulic lifters, though I suppose one could make it work.
 
If it bugs you you could enlarge them, but I don't think it will be a problem.
 
I imagine so AJ, with one or both of the galleries shifting. Not sure how the drilling of the galleries would have not cleaned some of that up however; it is almost like the drilling followed the shifted galleries, rather than a fixed location.

I probably should take good look at the lifter bore locations too now; not sure yet how I am going to check that.
 
More like jsut a wandering drill when they bored the oil galley. The rest of the lifter area looks dead on. Core shift would shift a lot more around, especailly the lifter bores themselves. They look fine. The galley holes didn't have to be very precise as long as they intersected where they were supposed to.
 
I agree.

With as tight of clearance as they have in the lifter bores, as long as the oil hole is there, it will get oil.

The different sizes could just be because they ran out of a particular drill size and substituted another...
 
I believe the galley ' s are step drilled. If they are drilled from the back, the front bores will have the smallest holes. If drilled from the front, just the oppopsite. Just a thought.
 
Well, on this 340 block, the smallest holes are in the middle and there are larger holes in both front and back. That is the case on both sides. So the casting or the drilling is not straight.
 
nm9stheham said:
Well, on this 340 block, the smallest holes are in the middle and there are larger holes in both front and back. That is the case on both sides. So the casting or the drilling is not straight.
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I really wonder if they were drilled from both ends. There are oil galley plugs on both ends of the block. It's hard to drill 30" through cast iron with out the drill leading off. I have read in Hot rodding Mopar small block books that you can drill the galleys out to the same size for more even oiling.
 
My thoughts are the lifter has a very small hole comparatively, so it will only take so much oil.
 
toolmanmike said:
I really wonder if they were drilled from both ends. There are oil galley plugs on both ends of the block. It's hard to drill 30" through cast iron with out the drill leading off. I have read in Hot rodding Mopar small block books that you can drill the galleys out to the same size for more even oiling.
Click to expand...
Now that would make sense; it is easy to see the drills being off-angle from both ends. You may have solved the mystery.....do you prefer the moniker of Holmes or Clueseau? LOL Tnx
 
toolmanmike said:
It's hard to drill 30" through cast iron with out the drill leading off.
Click to expand...

Not if they were gun drilled, which I believe they probably were. Cast iron drills easily. Plus it's more like 22" depth. When they drill gun barrels, length vs drill diameter can be huge, and those holes are straight & of constant diameter. Besides gun barrel material is a lot tougher than iron.
 
69_340_GTS said:
Not if they were gun drilled, which I believe they probably were. Cast iron drills easily. Plus it's more like 22" depth. When they drill gun barrels, length vs drill diameter can be huge, and those holes are straight & of constant diameter. Besides gun barrel material is a lot tougher than iron.
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Even the oil passage from the mains to the lifters was step drilled. Multiple spindle radial drills in industry don't have much stroke and breaking a 2' drill off inside a block can cause a lot of scrap or rework. When I worked in the machine shop on the automatic screw machines, we step drilled 6" idler pins in 3 steps. I could run 500+ pieces in steel without breaking a bit. You have to get the shavings out of the hole and you can't do that with a 24" bit. How to Hot Rod Small Block Mopar Engines even states "But in some cases, the blocks are machined in production using a stepped drill. This means that the top part of the passage is smaller than the bottom."
 
Now I am gonna have to peer into the galleries from the ends when we get the block back.... from the machine shop trying to deck it square to the bores... again.

I guess I would not expect engine production machining to be of the same caliber of gun barrel drilling (no pun intended).... there is just no need to do so for an oil passage.
 
nm9stheham said:
Now I am gonna have to peer into the galleries from the ends when we get the block back.... from the machine shop trying to deck it square to the bores... again.

I guess I would not expect engine production machining to be of the same caliber of gun barrel drilling (no pun intended).... there is just no need to do so for an oil passage.
Click to expand...

Yes it would be interesting to find out. I would also wonder about the feed passage from the mains up to the lifter galley.
 
The breaking of drills also depends on the diameter.

We had fits with the oil squirt holes in the connecting rods. The small diameter drill bits would break off and then the squirt holes would not be all the way through until they caught it...

The lifter galleys can take a larger diameter bit, which should be more "stable" when drilling longer depths....
 
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