Copyright WWW.DBBP.COM | updated 20-June-2016


Last week we welded up the oil return hole, as I am using external oil returns. After the weld had been smoothed and the external oil return testfitted the next step was to convert the heads for use with my 3 5/8" bigbore cylinders


To install the new Kibblewhite cast-iron valveguides I machined 2 aluminium tools, the first a support that fit in the intake valveseat with one side and in the exhaust with the other side. The second is a piece that fits in the valveguide so I can whack it with a hammer without damaging it. I heated up the heads to about 150 degrees C in my oven and cooled the valveguides with Loctite "Freeze and release" spray. The valveguides went in with a few taps with the hammer.


After all had cooled off we measured the diameters of the hole in the valveguide and the valvestem; the hole was 0.12 mm too small. This is normal as the valveguide will shrink a little bit when installed, so we used an adjustable reamer and carefully made the hole 0.10 bigger. For the last 0.02 mm we used a "Sunnen" honing machine as this gives the best possible finish. Of course each valve and guide were measured separately as there are small differences in valve stem and valve guide diameters.


Next step will be machining the valveseats, to be continued...