I'm nearing completion on my 305 rebuild, and now I've come to the point where the valve seats needs to be refreshed. I don't have the money to get a proper machine valve job, and I don't have the equipment to cut and grind them myself. So I bought some valve seat grinding paste, coarse and fine, and the wooden stick with the suction cup to rotate the valves in their seat. Now, my dad talked to a mechanic about it and he said that they have to be rotated back and forth (as apposed to hooking the valves up to a drill and let 'em rip, which was my original plan) to avoid getting rings in the seats. But wouldn't you get rings either way? It shouldn't really matter which way they rotate or if it changes direction or not, should it? If rotating by hand till my palms bleed is the best way then I'll do it, but if any of you have a better way them I'm all ears.

Also, the valves need back cutting, at least the exhaust valves. Here, I'll show you:



Now, here's the part where I get confused. Am I supposed to cut it straight as indicated by the red line, or more of a round shape like the blue curve? I read through the .-thread, but nearly all of the pictures are gone from it, so what's left doesn't really make sense.
Any input would be appreciated.

Thank you

 

i've done the drill before.(low speed) just a few seconds per valve. you can do the fine by hand. make sure you remove all the compound. when they're assembled you can check the seal with some brake clean. i rebuilt a customer's heads this way, he could stop talking about how good it ran.

 

Ok, so low speed drill seat grinding - check!
Do I need any for of lubrication in the valve guide? Some WD40 or the like?

 

This is the correct way...


http://www.v6z24.com/howto/valvelapping


however i've used a drill before, 1-2 sec per direction works ok.

 

some engine oil on the stem

 

oh cool, my thread got some use!
I'll dig up the photos on my computer at home. Unfortunately once I gradded from university, they removed my filespace, and I totally forgot what I had used it for.

PM me, or something if I forget, but I should have these pics on my computer at home.

 

I just lapped a set in tonight, no drill but i did use some assembly lube on the valve stem.


make sure to clean out the guides really well, mine came out of the blast cabinet and still had some media down in there.


On a similar note.. anyone else find that the suction cup lap tools really suck? I think i'm going to pick up some neodym magnets and try to make one that holds better...

 

I'll second that. Not only does the suction cup keep popping off of the valve, but the wooden handle keeps spinning in the base of the suction cup, so for every three revolutions the handle does, the valve only does about a half. But the neodym idea sounds like its do-able. I actually have a set of them lying around in a drawer. I'll have to try that one out. Thanks.