Doing a stock rebuild on my 340 and the rods have pin bushings but no oil holes, I kinda like the idea of the pins getting at least a little oil so I'm thinking before I have everything balanced I'll add the hole(s). Two different ways I'm thinking of, one hole in the top of the rod or two holes with one on each side toward the top. Any thoughts on which one would be better? What size should the hole be? Thanks
Wrist Pin Oil Hole Info
- Thread starter kend
- Start date
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yellow rose
Overnight Sensation
One 3/32 hole from the top.
rustycowll69
Well-Known Member
the oil spit hole on the big end faces the cam.
nm9stheham
Well-Known Member
Mmmmm.. the holes have to line up with holes in the rod bearing shells so I would assume that the drill has to start from the inside of the big end bore. The hard part will be figuring the angle of the hole and making the drill start and follow that angle. IIRC, the angle is not perpendicular to the big end's hole bore. You might have to start a bit larger hole perpendicular to the bore so the smaller drill has an edge to start on.
FYI, make sure your 2nd ring and oil ring fits are good. Sometimes (not always) this extra oiling leads to more cylinder oil consumption; some of it ends up on the cylinder walls and the rings have to control that.
FYI, make sure your 2nd ring and oil ring fits are good. Sometimes (not always) this extra oiling leads to more cylinder oil consumption; some of it ends up on the cylinder walls and the rings have to control that.
famous bob
mopar misfit
unbelievable--------
Let's get this back on track! A single hole from the top 3/32 like Y R said and do a health sized chamfer at the top by using a larger drill bit, make it about 3/16 wide.
MRL Performance
Well-Known Member
We drill an 1/8 hole right on top, we also put a nice chamfer on the hole as well to help aid in the oil getting to the pin. Dont forget to debur the bushing as well.
rustycowll69
Well-Known Member
I was referring to the factory spit hole notch in the connecting rod big end and matching cap. The only reason I brought it up is because you need to mount the piston on the rod in the correct orientation, so that the piston offset is correct AND the spit hole still faces the camshaft. I don't know if somebody else''s sarcasm could be misconstrued or not, but in no way, was I suggesting somebody drill anything in the big end of the rod.
Is this just info or does it have something to do with the wrist pin oil hole?
Dafuq does this mean? I got lost after mmmmm....
yellow rose
Overnight Sensation
I think nm9 was thinking about an oiling hole that is from the top of the rod bearing hole through the beam to use pressurized oil to feed the pin.
I did forget to mention to chamfer and deburr the hole, but I just take it that everyone knows it and does it.
Gotcha. That is way too much work for this project, thanks!
yellow rose
Overnight Sensation
If I was wrong, I'm sure he'll chime in and fix it, but I'm pretty sure that's where he was at!
nm9stheham
Well-Known Member
Yep..... and angled hole was what I assumed the OP was talking about. AND then I was mixed in some /6 rods thinking with the bearing hole location..... oooops! My mistake. 
Try this. see post 2,7 and8
rustycowll69
Well-Known Member
yes, my comment was added info, because it seemed apparent to me from the question, the OP may be a relative novice at 340 assembly, and is probably going to put together the rod/pin/piston assembly, himself. I was trying to be proactively helpful. If assembled incorrectly, he could have excessive noise, vibration, and premature cam wear problem, to name just a few. I know I don't want to pull a freshly rebuilt engine apart, again, so I assumed OP would feel the same way. IIRC the 3/32" comment reflects the Direct Connection Racing Manual instructions.
Thanks for the info, done a number of engines but this is the first 340.
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