Cutting down valves

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rustycowll69 said:
I don't know about saving all valves, though. Valve stems can wear like an hourglass and that makes them hard to get an accurate and consistent guide to stem clearance. Unless you run positive stem seals, you are losing vacuum to too wide of clearances.
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I mic the stems and always run a positive seal. Unless you are pulling pan vacuum then you can leave off the seals and save some power.
 
yellow rose said:
I mic the stems and always run a positive seal. Unless you are pulling pan vacuum then you can leave off the seals and save some power.
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I DIDN`T READ THESE POSTS , but I wouldn`t do it in a lathe !!---------valve machine !
 
famous bob said:
I DIDN`T READ THESE POSTS , but I wouldn`t do it in a lathe !!---------valve machine !
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There is no problem doing this in a quality lathe or what I use --a Hardinge collet lathe as someone mentioned. I have a nice piece of plastic that I use on the center to apply pressure to the valve head to remove vibration. Titanium and stainless are not a problem. J.Rob
 
Thanks again guys. It’s not something I’m going to jump into soon as I’m pretty well stocked up on valves right now but at least you guys helped me confirm my thoughts that it could be done. I may try both machines for the heck of it. My lathe is just an older sears craftsman model with a 4 jaw chuck and some attachments.
 
rustycowll69 said:
I've never done it on a lathe, but I think it would be much better accomplished on a valve refacing machine. I think the material valves are made of would be more easily ground, than cut with a tool.
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RAMM said:
There is no problem doing this in a quality lathe or what I use --a Hardinge collet lathe as someone mentioned. I have a nice piece of plastic that I use on the center to apply pressure to the valve head to remove vibration. Titanium and stainless are not a problem. J.Rob
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That is what I fought, the vibration. So I just found it easier with the valve machine. Slower......but easier.
 
IQ52 said:
That is what I fought, the vibration. So I just found it easier with the valve machine. Slower......but easier.
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Yeah, I should have mentioned that. The smaller the stem to worse the vibration. I set a rear stop so all the valves end up in the same spot. And I keep the valve head as close to the Chuck as I can. That helps a bunch. I need to look and see what insert I used and that thing eliminated 99% of the vibration issue.

I leave the valve .002-.003 big and run a file over the OD to size it and run them.
 
Theres a guy in Dee-troit that cuts down used nascar Ti valves both the head and stems. Going to have him do the valves I have for my next Gen3 Hemi build.
 
pittsburghracer said:
Thanks again guys. It’s not something I’m going to jump into soon as I’m pretty well stocked up on valves right now but at least you guys helped me confirm my thoughts that it could be done. I may try both machines for the heck of it. My lathe is just an older sears craftsman model with a 4 jaw chuck and some attachments.
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You can do some pretty impressive work on those lathes if the bearings are in good shape, use SHARP tooling, and you take your time. Bed wear can be worked around. They aren’t real rigid machines so typical carbide inserts may be too blunt. Hand honed carbide or quality HSS tooling will give best result. The four jaw is slower to set up but can be dialed in to a couple tenths if needed. Most three jaws have 2-3 thou runout at a given diameter which may or may not matter depending on what you’re doing.
 
gzig5 said:
You can do some pretty impressive work on those lathes if the bearings are in good shape, use SHARP tooling, and you take your time. Bed wear can be worked around. They aren’t real rigid machines so typical carbide inserts may be too blunt. Hand honed carbide or quality HSS tooling will give best result. The four jaw is slower to set up but can be dialed in to a couple tenths if needed. Most three jaws have 2-3 thou runout at a given diameter which may or may not matter depending on what you’re doing.
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lathes like a Craftsman are really just hobby lathes, so it's a little iffy on what kind of fine work you can do on certain materials, but a real deal machine lathe can do it, without much fuss.
 
rustycowll69 said:
lathes like a Craftsman are really just hobby lathes, so it's a little iffy on what kind of fine work you can do on certain materials, but a real deal machine lathe can do it, without much fuss.
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It’s more the injun than the arrow, but light or worn machines do have their limits.
 
gzig5 said:
It’s more the injun than the arrow, but light or worn machines do have their limits.
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worn or poorer quality spindle bearings, or straight cut headstock gears can contribute to vibrations, this will be reflected in an uneven ("chattery") finish. That said, you probably won't know unless you try it. What is undesirable by some, might be perfectly acceptable by others
 
I've had 2.02 cut down to 1.88. But the installed height on the valve springs will be changed relative to uncut exhaust valves.
 
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