Okay, so yesterday I got an hour long class from an experienced machinist on how to use the machine at my local hobby shop on how to cut valve seats. I have a few questions for anyone who might be experienced or can add any insight.

From what I was told, your average 4 cylinder motor that was built during the late 80's throughout the 90's and even more recent come with a 3-angle valve seat. He told me the typical cuts for those grinds are 46*, 16*, and 60*. I believe in that order as well.
I was thinking about picking up a bare head for like 50 bucks and giving this a go. I was even more curious if anyone know what ways one would go about cutting out a 5-angle grind. What are the degress of the cuts typically used? Is this something you really only want to do on a over-sized valve?

I noticed on a demo head we pulled out of the metal bin yesterday (a SOHC saturn head) that a 4-angle brought the seat EXTREMELY close to the edge of the valve, allowing for VERY little error margin. I was told the benefit of it being this close to the edge of the valve was that the air could move in/out past the valve faster/sooner as it didn't have to open as far before the air could move.

I read in a thread on here about valve jobs also, that we have 3-angle from stock, but typically after 100k+ miles these seats become worn out and can use a 'refresher' cut.

If anyone could just give me a little more information on the benefits of a 5-angle cut, the actual angles used, and whether or not it's only probably on a over-sized valve versus a stocker, I would appreciate it.

I'm not really worried about how practical this is. I just really love digging into machine work and this is something new and fun for me to try with only 50 dollars at a loss if I jew up the head.

Also, would I be more better off for the size of my build (profile) to just try and re-cut/refresh the valve seats up and go from there. I was also going to try and clean all the valves really well, give it a little DIY port work to help increase overall flow of the head, and just overall make it a nicey shiney whistle again that can flow better than something with 15 years of gunked up abuse.

I don't know the angle values for a 5-angle (check Google, there'll be dozens of articles about it).
The returns are seriously diminished when you have forced induction.
Exhaust valves are cooled by conduction up the valve stem and to the guides, and out of the valve head through the seat. Smaller contact surface width at the sealing ring will reduce valve cooling- not something you want to do with turbocharging.
An alternative to a 5-angle job (which is one thing when you're fiddling on a hobby, and another when you're dealing with 16 seats and paying for it) is seat smoothing, where you hand-shape the corners of the valve job with a hand grinder and a sandpaper drum. The seat is then hand-lapped to the desired width.
Somehow, valve lapping seems to have become a skipped step. I don't doubt that it's redundant, but I also believe it's worth the effort.

Defiant said:

Somehow, valve lapping seems to have become a skipped step.

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Skipped how? As in shops don't do it anymore? Or as in people doing their own jobs don't do it anymore?

So, basically you mean cutting your valve seat angles to ensure the proper seal at the base of the valve. Then going back and every so subtley shaping/smoothing the inner, non-seating angles to provide a very smooth, transient flow?

Yes, any area that isn't in the actual seating ring of the valve and seat, just smooth it back. Take as little meat as possible from the valve seat. But again, with forced induction, there's not a lot of point. Now, true you'll get better "off-boost" performance (by a remarkably tiny increment), but if you have a turbo, just use the damned thing.
It's like the idea of wanting to make up some kind of part-throttle nitrous scheme. Everyone wants to cheat and get more power all the time, without the penalties involved (engine load/stress, fuel consumption) when just using the throttle.

I've had more than one member here react with surprise at the idea of lapping valves. Beats me.

Defiant,

My old man has a pair of Gurney Weslake heads on the 289 in his mustang. When he got them they had radiused seats. Is it possible that the seats were actually ground on a radius? Or just smoothed as you said earlier. These head were pretty trick in the 60's He got them in the early 90's off of a alcohol injected drag boat.

Honestly, it makes sense to me to blend all the angles aside from the actual seat. I might not know much, but logically thinking the smoother a path is, the easier it is for the air to move, correct?

That's generally my understanding anytime I port something. ie making a mirror polish for a turbo's hotside to prevent accumulation of build up and as fast and direct a path as possible with minimal 'angles'.

I was talking to that guy again, codenamed "Shorty", who is this really old machinist who used to work at the place where I do all my work. He said the reason behind using "multiple angles" is that it increases the velocity of the air.

Wish I had a flow bench there to try some of this out and actually test it.

well i saw that you would like to try it on a bare head. i have a bare 6 bolt head, if you interested just shoot me a PM.

I was just going over some of this stuff and there's a really nice writeup of this info here http://www.dsmtuners.com/forums/articles-engine-fuel/303225-engine-machine-work-explained.html


Here's a short excerpt:
"Most of you have herd of a 3 or 5 angle valve job before, this refers specifically to the number of angles machined on and around the valve seat. Most valve seats use a 45 degree sealing surface; the other two or four angles can be referred to as entry and exit angles. For example a 3 angle valve job with a 45 degree seat would also machine a 30 degree exit angle just below the valve seat on an intake port (this would be considered an entry angle on an exhaust port), and a 60 degree entry angle just above the seat on an intake port (& vice versa). A 5 angle valve job typically adds 15 and 75 degree cuts to the ones mentioned above. This process is intended to create a funnel leading into, past and out from around the valve itself. "

As for smoothing out the angles before and after by hand, this can cause a problem with different flow rates between cylinders and uneven surfaces for any future machine work that needs to be done. If you're just testing it out and you can ensure that you'll get even work done all around, go for it. I love breaking things doing stuff that I know won't work just to learn about why and how. I am really a hands on person; then again, my gsx isn't even running right now

This is exactly right pertaining to the valve angles. The 46 degree angle referenced from the OP is called the interference angle. It is or was used in the assumption that the slapping of the valve face and the seat would just break in and seal properly. You can use that method, but my machinist who over viewed the work I did on my built head told me just to go with 45. The process is as followed:

Get a 60 degree grinder/cutter and do you throat of the valve entry until concentric. After that, get your 30 degree grinder cutter and do your top angle until concentric. Once that is done, this is where you have to pay particular attention. Do your 45 degree angle seat. But do this step little by little and checking it with Prussian blue after every attempted cut. What you are looking for in a general valve job is to get the ring of Prussian blue about 1/8 of an inch wide in the center of the valve face concentric of course. If it is not centered, this is where you adjust your 60 or 30 degree angles (cutting) to move your seat up or down on the valve. Also, the seating width varies from intake and exhaust valve. Since the exhaust valve is going to see more heat, make the valve seating width a little wider. There are a lot of factors to consider, but that is basically a basic valve job, also making sure the each and every valve after the first one you do look and are cut the same.

Note: After cutting your valve seats, you can lap them to assure that there is a good seal. Just make sure you wipe off the lapping compound after your done or just put it in a solvent parts washer then flush with water and dry.

KJ

architechnik said:

I was just going over some of this stuff and there's a really nice writeup of this info here http://www.dsmtuners.com/forums/articles-engine-fuel/303225-engine-machine-work-explained.html

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"Third is a mechanism for facing the tip of the valve stem, this is needed to correct the stem height of the valve when installed in the cylinder head. This is typically a rotating stone and pivoting valve holding mechanism with a micrometer adjustment wheel. This adjustment wheel allows very specific amounts of material to be removed from the valve stem. This is a very important step, when the valve face is cut it moves the valve toward the cam, rocker, or lifter depending on the engine type. Machining the valve seat has the same effect. Therefore if .015 is removed from the valve, and .020 is removed from the seat .035 must be removed from the valve stem tip. In order to maintain the correct hydraulic lifter preload, or to maintain a specified valve lash setting. Failure to do so will result in incorrect valve lash setting, too much or too little lifter preload."

This is the only thing I was worried about when trying this. I was thinking that something like this might happen if you cut out of the valve seat area, thus causing the stem to move closer to the cam/rocker.

I'll have to check tomorrow if my shop even has this machine.

LOTS of good info in that thread. Thanks for finding it!

bastarddsm said:

Defiant,

My old man has a pair of Gurney Weslake heads on the 289 in his mustang. When he got them they had radiused seats. Is it possible that the seats were actually ground on a radius? Or just smoothed as you said earlier. These head were pretty trick in the 60's He got them in the early 90's off of a alcohol injected drag boat.

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They were probably finished by hand, especially if they're from GW. You'd play all kinds of hell trying to get the stones profiled in order to be able to get them to blend a whole head's worth of seats. It's not that hard a job, it just takes concentration and focus. Real machinists are always a little odd.
True that without a flowbench, all this "feels right" work can have a negative effect. You're dealing with a dynamic set of values that are doing all manner of inter-related functions over all kinds of variables- throttle plate angle, plenum pressure, flow rate, acceleration issues, gas hamonics.... it's overwhelming. Getting it "right" once, at a given flow under given circumstances is a fluke. Getting it the same four times per cylinder is all but impossible.

I'd thought 1/8" might be a wider seat surface than you'd hope to get on DSM-sized valves.

don't machinists have seat cutters that can cut multiple angles at the same time?

There are still some machinists that still stone grind valve seats but alot of them are using cutters that will do all the angles. The beauty of this is that you can pick any combo you want right out of a catalog and if its not there you can call them up and they will make a cutter for you. From bowl hogs to radius cutters, its all in a catalog.

As for the diy valve grind, its possible but you will need a fair amount of tools. You might as well find a community college or a trade tech school that teaches engine machining that also still has provisions for stone grinding valve seats or old school machining. Controlling seat width and seat run out is something your not going pick up easily especially if you are stone grinding seats.

I'd like to see what the concentricity of a diy valve seat looks like...

GVR4592 said:

I'd like to see what the concentricity of a diy valve seat looks like...

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I think that would depend on how much that individual has had to drink.