Aftermarket Chief Rods

[Bills37]

Ok, I'll start with a little background. I'm helping a buddy with his 53 Chief engine that he has someone start on 4-5 years ago and couldn't seem to finish. Long story short a lot of these parts were already bought and I have no idea of the provenece although I suspect they may be Eastern stuff. The problem I'm having is when I torque the crankpin nut up the forked rod drags slightly againts the inside of the flywheel at TDC. I pulled it back apart and checked it againts an original and the rod is thicker in that area. I'm thinking of taking a die grinder and remove a little material. Maybe .060 - .080.
Anybody run into this problem before?

[exeric]

If the threads on the crankpin, or crankpin nuts are not cut perfectly perpendicular to the centerline of the crankpin you could have that condition. I recall reading about an original condition Chief that had such a problem from the factory and the wheels could not be trued. It might be worth setting up the crankpin in a lathe with a nut screwed on, and then using an indicator on the thrust face of the nut to see if there is any runout.

[fillibuster]

If the threads on the crankpin, or crankpin nuts are not cut perfectly perpendicular to the centerline of the crankpin you could have that condition. I recall reading about an original condition Chief that had such a problem from the factory and the wheels could not be trued. It might be worth setting up the crankpin in a lathe with a nut screwed on, and then using an indicator on the thrust face of the nut to see if there is any runout.

I want to suggest, first, that a die grinder shouldn't be your tool of choice for planing the outsides of the forked rod. Find somebody with a vertical mill. You'll have to remove the rod races first. If you're in the deep woods you could get a way with using the side of a chop saw blade, halving the removal on each side, and using a caliper. Remember that the races protrude past the rod body (check the specs). Remember also that your crankpin thrustwashers come in various thicknesses to achieve spec'd clearances.

One has to consider checking for perpendicularity of each shaft in it's flywheel before full flywheel assembly, and protrusion beyond flywheel face. You need a dial caliper for that, and a dial indicator on a magnetic base. Each alignment step you take in pre-assembly is worth a lot in the final assembly. It can mean the diff between in spec and way out of spec, and pissed off!
You're probably p.o.'d already.... be patient, it's worth the diligence.

Eric, non-perpendicular threads? Wow, I wouldn't have dreamt something like that, but I have a trans main-shaft that seems to have its center hole off-center by .006 on the extreme clutch end (that's .012 overall as it rotates). From there, it measures .009 at beginning of spline, .004 at opposite end of spline, and .002 at output gear area, and zero next to output end. Been running it for 15 years. Makes me wonder/ponder how some of these machine processes went, chronologically, like maybe the centers DIDN'T dictate the rest of the shaft's processes. .. I've never been proud of my clutch, but I don't think it's been running out of true. The side-car used to make it "grunt", and it suffers from "grab" in the slow races, but it's logged a lot of distance. I think I'll run it some more.

[exeric]

Phil, I do my own flywheels and it can be quite a chore. I look at every component that goes into the flywheel assembly because everything has to be perfect for the assembly to work. From a machinist's perspective; if the threads were put in the nut as a second, or third operation, it's quite possible there was a burr, or a chip in the fixture and the nut was not properly seated. Crankpin nuts are not a high production product, and by function, they have to be extreamly precise. I have a friend that got an Indian crankpin from a reputable company and the pin (at the tapers) was too long by over .070". That problem was hard to find because you assume it's a quality part, also his wheels trued up perfectly. Machine work is all about maximizing accuracy, and minimizing error. It sounds simple but airplanes still crash because of problems with simple nuts and bolts.

[Bills37]

Thanks for the input. The area I was talking about is above the race journals where it tapers into the "neck" of the rod. The new rod is thicker in this area and is rubbing the wheel on one side. I have a Bridgeport mill but that seems a bit extreme for what I'm talking about not to mention the difficulty of machining a compound radius with a manual machine. Seems to me that a die grinder with a soft ruby stone I should be able to remove a slight amount of material and maintain the proper contour. I'm curious if anyone else has run into this sort of problem.

Oh and for further clarification I put both wheels individualy on centers in my lathe and they both ran dead true. Truing the wheels isn't really the issue. Yet.

[redfred84]

I've had issues with the crotch of the female rod needing to be ground away for clearance. A critical area. But this situation happens towards BTC.
RF.

[fillibuster]

Thanks for the input. The area I was talking about is above the race journals where it tapers into the "neck" of the rod. The new rod is thicker in this area and is rubbing the wheel on one side. I have a Bridgeport mill but that seems a bit extreme for what I'm talking about not to mention the difficulty of machining a compound radius with a manual machine. Seems to me that a die grinder with a soft ruby stone I should be able to remove a slight amount of material and maintain the proper contour. I'm curious if anyone else has run into this sort of problem.

Oh and for further clarification I put both wheels individualy on centers in my lathe and they both ran dead true. Truing the wheels isn't really the issue. Yet.

Ah-sooo. That sheds a little light.
Hope your problem is less work than fitting cast-in-India cyls. Yeah, die-grinder. ... I was thinking 9", .. earlier ... lotta tolerances in them Indians