Wrist pins

2

2speed

Senior Member
Burtz Block/Connecting Rods with Egge Pistons.


Wrist pin is tighter to push in the connecting rod than in the piston. Pistons are nice easy slip fit, rod is a good push. When together wrist pins rotates in piston, not the rod. Since I don't have thousands of dollars in internal mic's, I'm not going to pretend I can measure a half a tenth. Am I going to need to take these somewhere and get them honed fit?
 
Yes, it shouldnt take them long at all. It happens. I have a set of pistons right now that
the pins are slightly too big. Another pin from another set just slid right thru just like she likes lit.
 
I would have the rods LIGHTLY honed on a pin-fitting machine. I use 600 grit wet-or-dry paper, and it only takes a few swipes to attain what you want.
 
Also remember that the pin fit is very close tolerance,even holding it your hand for a few minutes can warm it up enough to increase it's diameter enough to cause a tight fit it your in a cold or cool shop.
Not your problem here but soming to remember
I assume the pins came with the new pistons and there fit should be good.
So fitting the pistons ok I would take the pins and rods to a machine shop and have them honed to fit the pins and you should be good to go
Simple job that only takes a few minutes to do.
Maybe take a piston and have them double check it's fit with the pins as well.
 
One other option is to use a penetrating Loctite in the pistons, making sure that it does not get into the rod.
 
I'm probably going to take them to a shop. But the correct action should be the rod spinning easier than the pin the piston correct? Do people really loctite the pins in the piston?
 
Full floating wristpins should float smoothly in the piston and the connecting rod. During assembly at room temperature it should only take a light push with your thumb to install the pin.
 
2speed said:
I'm probably going to take them to a shop. But the correct action should be the rod spinning easier than the pin the piston correct? Do people really loctite the pins in the piston?
Click to expand...


The pin should fit just a bit looser in the rod bushing than in the piston. The piston quickly heats up and the clearance there increases,while rod bushing clearance stays fairly consistent. A good pin fit allows the pin to just fall through the bushing by its own weight. A light thumb press in the piston is fine.
No...people don't loctite pins in pistons. :eek:
 
Pins fitted to pistons in southern California and the sent up to the northeast during the winter where often very difficult to remove often needing heating of the piston to get the pin out. If you bring your rods to a machine shop to be honed be sure to bring two wrist pins. If the shop is properly equipped they will have a fixture that holds two pins and then is used to set the AG300 gauge. The proper hone has bronze shoes not the aluminum throwaway type of hone. Proper fit is usually .0003-.0005. a few strokes with a fine stone will do it. There is enough variations in wrist pins that this may occasionally be needed. No big deal. Model As have full floating pins.
 
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