Robs Howell V4

[gbritnell]

Rob,
Start out by making a tool like the one attached. Lightly cut the seat. This tool will ensure that the seat is concentric with the guide hole. After that put a little lapping compound on the valve and insert it into the head. Attach a small drill chuck or pin vise to the valve stem. Rotate the valve back and forth while every couple of cycles lift it off of the seat to redistribute the lapping compound. It shouldn't take much to lap it in. To test I make up a bushing adapter for my vacuum gauge. The one end will have a diameter a thousand or two larger than the port diameter. Then file a tiny taper on it. You can wring this into the port and attach the vacuum gauge or just a piece of tube and suck on it. Make sure you put a drop of oil on the valve guide to seal it while checking.

 

[RobConway]

Been chasing the runout in the lathe chuck for the machining of the valve seat. Replaced the 3 jaw chuck and fitted the ER32 collet and now have a runout of 0.01mm. The 3jaw was 0.08mm runout.

Had to get a wide mouth wrench for the chuck as really needed to tighten down the collets to align properly. The flats on the chuck were 36mm so had nothing that big.

 

[dsage]

Rob:
Go back one post and make the valve seat cutter George recommends. Works a charm.

 

[RobConway]

For whatever reason my seat cutter lost its cutting edge after only 4 seats. Assume I didnt heat treat properly. I did struggle to grind the relief on the back of the edge. In saying that the two valves I lapped in did hold pressure OK. So I may need to make another cutter for the other head, maybe this time I might make the cutting edge a little "deeper" as assume the only place its cutting is the corner where the 45 deg edge meets the port shank and I have trouble grinding that relief. I had thought I could of machined the relief on the mill but the compound angle did my head-in how to set it up. I had thought I would simple turn the cutter 15 deg in the collet then clamp the collet at 45 deg but didnt realise I need to turn the vice on another angle of ??. So did my best on the 6" grinder by hand. Anyhow if it means making another cutter for the other head thats fine as it seems to work fine on the valve seats I fitted so far. I did learn 1. how hard it is to remove ALL lapping paste -had to get some brake cleaner and 2. went too hard on the first valve and the 600 grit took too much from the SS valve. So had to skim that valve and do it again softly. Have ordered some 1200 grit silica carbide as thinking 600 was a little too course to finish off with.