TOPIC:

Kawboy and I have had some offline discussions on valve clearance. I thought this basket case motor would be OK as it had 230/235 shims and I only cleaned it up and lapped them lightly...

I was wrong. All intakes have 0 clearance. Tried one with no shim and it looked like It would need a 185 shim. Which of coarse is not possible.

I’ve got 1 intake valve out and it has an A dim of 4.94, so I am grinding tips. Hope the rest are the same!

Got this finished this evening. Had planned on using the tool post grinder on the lathe. Got it out and setup, only to figure out I had no grinding wheel for it. Jury rigged a drill in the tool post since I did have a small grinding wheel for that.

All of my valves were close to 5mm for the A dimension. So removed .3mm from each. PITA without a proper valve surfacer.

I also compared the intake valves with a new one. Head dimensions look identical, so it’s not like these valves had been ground on before.

On one valve I was nervous the keeper was so close to the valve tip - if the bucket runs on the keeper it will likely drop that valve. So I did trim that one keeper. If any of the valves where at the book limit for the A dimension, the tip would be below keeper.

Put the intake cam in to check and all looks good. I will now need a whole new set of shims.

Before




After

I'll be interested to hear what shims you ended up with and how many miles on the road you get in before running out of shims. .3 mm (.012") you managed to grind off and you needed .005" for clearance leaving .007" for shim thickness above the minimum 2.00 mm shim so you probably end up with 2.05 mm or 2.10 mm shims.

I was just going to ask you Frank if you have a proper valve grinder, and I see you did it the alternative way.

Looking at the close up after photo, the tip seems kind of rough and raised. Is it flat and it's just the shadow? I'm wondering if there are any ridges, they would got beaten down with use and rather quickly change the clearances. I know they are installed now, but I'd probably use a diamond file and 2000 wet paper to carefully even that up, with a steady slow hand.
I've done that with the manual tensioner - it had a dome and I ground it flat, and 'polished' it with a 1500 and 2000 paper.

Kawboy,

Ah, but the shims in it where 220-245 before grinding. So many may have been shimable. I ordered shims today. Shooting for MAX clearance called for in the book, I need 1 x 210 (which is a worry), rest are 235-265 (some of the exhaust had ample clearance before grinding). So the 210 one will only survive one adjustment before needing a seat.

Figured I am going to ride it until it needs a seat. The chains in this motor are fair, but not great. So it's not going another 60,000 miles before major work anyway.

Stan,

You are correct, the center is rough. I hit the tips with 800 paper (wrapped around a file) while still in the lathe. It looks like in doing so I really only polished the edges. There could not have been any dome before that point, but I expect there is a bit now. I am sure it will hammer itself smooth quickly. Those pictures are REALLY zoomed in. I don't expect it to flatten more than a thou. That may increase clearance slightly, but the freshly lapped valves will do the opposite when they bed in.

Keep in mind we mostly build race cars here. Both Open Road Race and Sprint Cars. In both cases, a full year of thrashing is less than 500 miles, and in case of the Sprint Car it will likely get destroyed once or twice in that year. So I probably tend to put a bit less finesse into projects