![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRAgV0K_be3ZQIUKol0cTKCbDUqjB0AXSG3HzXGAoDByvqkOkQT9gsB7Yvy5dEgXbznXgVLdbZbqTnXslLn87cWCbFeZLQHSdA_zXeMLEnOZxCGYeFjDrzxT7XNzJ-Vb0aus0SY70GNp8/s320/P1030202.JPG)
This is what a knucklehead that has been converted to run
pan head cylinders looks like. This was a popular deal back in the seventies. Chopper guys and girls used to have a hard time finding low bore knuckle cylinders, so they would use
pan head cylinders. Four of the bolt holes in
pan head cylinders are the same as a knucklehead, but one of them is in a different spot, so they would screw a head bolt into the hole, and drill and tap a different one.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjzBcUmzOWVtQ-Zi0At9OjJmaJBGlop2XR_6FF9W7umY8wMzImIEqlyT5xo6LkpKhdwTfoLSSV8nGAU9yc_QRKoejbYwdTcOL_7ddlMQlIsAIKTMogu3swTYzP40Pv1dEF5iFgSfKvHZY/s320/P1030188.JPG)
The first step in changing the heads back to stock is drilling out the head bolt hole.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmPCD3YpT3MLjR0bGLpSZ4bzRmAcPowubr13wdkJRQVnp_bbRmcuGIQqOaqgclZ5wBK3X6pTfwJQsmQqEnYJyPxGD1kUHtAAp484Ob-Pz2Vex3Y2O2fWn6hIF8uZE1i_uVC6wP0i3DQqY/s320/P1030194.JPG)
Then you put a bolt in the hole that was
previously used for the pan cylinders.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjirRej1uybmJ5KbMc4dGe6nn15Rh3HClbo8FaBfX6nIxNy1wHl5tFqHtFTf5OE9F9_dRzeHQbo8mWecA_khO8Wj33R36qbsJ-UsJ40iS4yCSO22YnSowN1-ZWax02sH_faMMTGm8K5XBM/s320/P1030196.JPG)
Next step is to drill hole for the knuckle head bolt pattern, then tap it for a
helicoil.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZoPlH_c_uAhgWvQNwRmcyN1AJVrENLbyoZG23W1UhS_aigaLRgS-C05OYVvceVWj9GccD1ckp6y58gDaf4GEmnwM9u1hBh2XgAnrPWXd6na0J9LSKoRPCA86Z6nrRgam3Y4yImFywX58/s320/P1030198.JPG)
Here is the almost finished product. we still have to face the head bolt surface, but you get the idea. This is a good fix and will last a long time.