Has anyone out there experimented with using a mill (bridgeport...) or other machining tools to speed up porting cylinder heads?

A couple thoughts that I've had were
- setting a boring bar to 85-90% of the valve diameter and plunging it into the valve throat cutting it to what is considered perfect size in a couple of minutes (blending by hand later).
- using a ball end mill to cut the intake openings to the gasket opening size, again, blending by hand.
- using a lathe to make a 30* backcut on the valves

Has anyone tried this kind of stuff? How did it work? Any other ideas?

 

I've never done it, but CNC mills perform the same types of things very commonplace nowadays for aftermarket cylinder heads, so this would just be a manual version of what these machines do. By nature, the bridgeport is going to accurate, but the setup is where you get your repeatability. One of the guys that was doing the high HP TPI setup, jerrywho maybe? had some pictures of all the aluminum plates and runners that he rough milled before porting blending and welding. There was also someone else I saw, maybe on turbomustangs, that milled his intake on a 5.0 to open up the runners. If the bridgeport has a power downfeed, you can get a really nice finish on a boring operation.

again, alot of the gain you get will be to blueprint out the ports with the mill before you even start cutting to make accurate cuts.

as far as valves, all a valvegrinding machine is, is a specialized lathe. they use grindstones, so if you end up using a lathe, the machine will need to be protected from the abrasive dust so that it doesn't ruin the ways.

I'd also venture to say you will need some good tool bits on heads if they are cast iron, especially if they are induction hardened near the seats.

 

depending on the port there are times when you don't want the area under the valve to be perfectly round. It might be worth exploring if you have access to a flow bench though.

 

Don't they all have a power downfeed? Mine the engagement **** was broken off when I bought it, I tig welded a nut to it, threaded it out and got a new one, but never played with the downfeed because the automatic stop kept popping and then my clock spring broke causing it to act like an automatic downfeed any time you released the spindle lock.

Even still, a steady hand will still give you a nice finish.

sounds like an excuse to build a toolpost grinder, but I'm not sure why you couldn't do it with a slow feed and a carbide bit...

 

yeah, I'm sure the carbide will work well for valves, though I think the grinding is so that the finish is close enough that lapping afterwards gets you a solid sealing surface.

I would assume most milling machines have a power downfeed, but there are so many variations out there, I figured there are some that don't.

 

The power downfeed ***** are all broken off in every shop i've ever been in. When we get new ones now, we just take them off. You can still use it when needed. Our older one did something similar, where the power feed was working great till the clock spring broke. replaced the spring, now the auto stop keeps popping out, so I just hold it engaged until it touches the quill stop then just let go. It's annoying, but works. We have a CNC, but it's 3 axis, so wouldn't be much more effective then what u are wanting to do, IMO, I don't see why it wouldn't work effectively for roughing in. I hate machining cast though, hope you are doing aluminum, or at least I would be if I was to do it.
As for the valve grinding, just for the backcut, I say go for it. You may have to hand polish it after to get a good finish, but with a toolpost it would be repeatable. I wouldn't do a valvejob on one myself, but the backcut could be a good idea. My problem would be our 12" 3jaw chuck would want to scar up the stems.

 

Just send it out for extrude honing...

 

I think you will spend more time setting it up than you will gain from just doing it by hand. You might gain some consistency, that would be about it IMO.

I think you'll be fine backcutting the valves with a lathe, but I'd find a valve grinder to do the sealing surface.

 

Make a little sleeve/bushing to hold them, something with an ID just barely larger than the OD of the stem with a slot down the side of it, as you squeeze the chuck down on it it will center itself (heck, if you can get your hands on a bronze valve guide you have a ready made bushing).

 

The right grade carbide will be wonders on the valves, we hard turn alot of stuff at work and when I first saw the process I was amazed. I try to leave that to the lathe guys, and stick to my mills. I've often wondered about porting on the mill, always wanted to try it but never did. Maybe I should play with the old cast heads I've got in the shed.