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Tractor Talk Discussion Forum

3 angle valve grinding??

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Lynn Kasdorf

11-12-2004 13:03:22




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I have seen various references to 3 angle valve seat grinding. Does this just mean that the valve seats have 3 facets rather than one? Why is this better?

I'm used to the old technique of valve compound on the valve seats and grinding them with a suction cup stick by hand.

I'll be doing the head on my 1940 JD B at some point, and woudl like to learn about this 3 angle stuff. Googling has not turned up anything yet.

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Frank Kovarick

11-13-2004 23:01:21




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
You're getting into racing applications with a 3 angle valve grind. Rather than a single possibly 30 degree angle on seat and valve face, the seat has the matching angle of valve to seat at the main contact area. Then in two increasing angle steps of maybe +5-10 degrees on the seat in the head, 2 narrower chamfers "blend" the area past the seated valve/seat to allow better air flow into the head passages. Nothing to gain as I can see for the effort involved in a tractor unless you plan to do "pulls" or other high revs things.

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Allan in NE

11-14-2004 04:42:31




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 Re: 3 angle valve grinding?? in reply to Frank Kovarick, 11-13-2004 23:01:21  
LOL!

Reminds me of watching a movie.

Yep, I'm certain that this is the point where I came in. :>)

Allan



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buickanddeere

11-13-2004 04:03:04




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
The gradual angle before and after the valve sealing area reduces turbulance so flow is increased. It also helps un-shroud the valve. A nail head shaped intake valve takes up less room in the flow path vs; a tulip shaped valve. Matching the manifolds to ports reduces restriction and turbulance. So does grinding off rough casting flash and sharp/abrupt machined edges around the valve guides. All this adds a little more "free" HP even in the most modest of engines. No rebuild should ever be done without doing a fresh re-grind on the cam to true it and the lifters up as well. A wee bit of a custom cam grind can really wake up some engines. As previously stated the old suction cup and lapping compound is only a trouble shooting tool. Square true seats/valves cannot be made with lapping compound.

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BushogPapa

11-12-2004 19:13:48




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
Many an old valve job was done useing only 1 or 2 cuts..one for the seat, and a "Narrowing cut" to move the edge of the seat in on the valve.. On 3 or 4 or 6 angle jobs, the INSIDE area of the seating surface is worked to a contour that flows the incomming or exiting gasses over the valve and seat more efficiently ( Like a Venturii) What I like to do is cut the valve face with 3 or 4 cuts, and polish the valve until the "facets" disappear and it takes on a "Tulip shape"...then cut a very fine single cut on the valve for seating purposes.. It is a Beautiful thing to see..and it DOES make more power.. I like about 1/4 degree interferance angle. Not for the "average Joe" , but once in a while I get to do one of my own.. What helps too, is to have the Block Bored with "Torque Plates" bolted on--simulating the torque of the head bolts...Then, using Gap-less rings for a near-perfect seal in the cylinder...

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jdemaris

11-12-2004 19:13:44




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
I'll try not to be redundant here and repeat what has already been said. I first read about "three seat" valve jobs back in the 60s in a racing magazine and never quite understood what they were talking about. I was wondering if they were actually making three valve seats instead of one - or just came up with new terminology to make standard procedure sound like something new. I still don't know. If you put a new valve seat insert into a head (or block for a flathead)it may be narrow enough where there won't be three angles. But, after grinding - or carbide cutting seats, they get wider - and thusly have to be narrowed back to specs. And, that's for at least two reasons. Number one, already discussed, is to get the correct width for valve cooling. This is especially critical in an air-cooled engine. Second - is to get the correct pressure on the valve seat. The spring on the valve provides closting pressure, but, if the valve seat is too wide - the pounds per square inch is lessened on the valve face and seat. As far as valve-lapping compound being obsolete, I disagree. A properly machined valve face and seat don't need lapping for proper seal - but a light use of lapping compound works kind of like Prussian Blue as a marker and lets you see exactly where the sealing area is. Sometimes, with a freshly machined seat and valve face, it's hard to see for sure. Lap it a little, and the sealing area gets dark and lets you see for sure. It takes a little extra time, but it sometimes exposes mistakes.

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george md

11-12-2004 18:09:00




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
Lynn,

Toss that head in your transportation of

choice and bring it up here. I'll do the

valve and seat grind while you watch.

george



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Lynn Kasdorf

11-13-2004 15:42:47




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 Re: 3 angle valve grinding?? in reply to george md, 11-12-2004 18:09:00  
Sounds great! Wanna email me and give me you phone number?

Thanks



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george md

11-14-2004 14:22:36




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-13-2004 15:42:47  
Lynn,

Did you get the mail ??

george



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Bob

11-12-2004 17:17:11




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
A three angle valve job will "flow" better than a simple valve job. Whether this has much bearing on a slow speed tractor engine is questionable. However, it certainly can't hurt!

Furthermore, if the valve and seat are ground with precision equipment, there is no need to "lap" the valves, and this is a throwback to the old days!



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Allan in NE

11-12-2004 14:27:44




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
Hi Lynn,

I guess I'm gonna end up being the odd man out and the bad guy on this one. 3-angle seat grinding has been around since forever; it is not a "new thing"; ask any machinist in any town, in any shop.

By grinding the seat at different angles, the sealing contact point can be moved either up or down along the valve face seating surface. If the contact point is too either too high or too low on the valve, the valve will burn. This is because with combustion temperatures at about 1200 to 1500 degrees, things are hot in that chamber and the valve has to be cooled by it’s being in perfect contact with the head and in a way as to transfer as much of that heat as possible.

Believe me when I tell you that anything less that triple grinding of a valve seat is nothing more than absolute, pure and unabashed "shade tree mechanics". Same old story: there is a right way and there is a wrong way.

Once again, just my view and stated as such.

Allan

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Lil-Farmer

11-12-2004 14:49:53




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 Re: 3 angle valve grinding?? in reply to Allan in NE, 11-12-2004 14:27:44  
I agree 100% with Allen. If I took a set of heads to a shop to have the valves ground and they weren't at least three angle with the seat contact area being 1/16 th to 3/32 nds wide, I wouldn't pay for the job. I have been grinding three angle seats for 50 years, ain't new technolgy.

Doesn't require anything but a stone that is more angle than the seat and one that is less angle than the seat. I. E. A 45 degree seat would require a 60 degree stone for the outside and a 30 degree stone for the inside. Use a tube of lipstick (don't tell the wife) and make marks across the face of the valve and use your suction cup to spin the valve in the seat to determine where the contact patch is; move it up and down and control the width by grinding outside or inside. Once it is where you want and the width you want, use some lapping compound to finish the job. Your valve job will last for yearas and years if done properly.

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Mike M

11-12-2004 18:51:55




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 Re: 3 angle valve grinding?? in reply to Lil-Farmer, 11-12-2004 14:49:53  
You maybe should tell the wife. As she is probabaly wondering why the heck you have lipstick hidden in your tool box ? The seat widths you state are more for the large valves found in these 2 cyl. tractors and the seat widths Allen states are more for smaller valves like car engines.Bottom line is follow the guide lines found in the service manual for your application. I also have been dumbfounded by this new discovery of 3 angle valve jobs. Mine have also always had this so I could get the seat where I want it.

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Lil-Farmer

11-13-2004 04:10:14




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 Re: 3 angle valve grinding?? in reply to Mike M, 11-12-2004 18:51:55  
Oh, I don't keep it in my toolbox, I put it back in her make up purse when I'm finished. :-)



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Allan in NE

11-12-2004 14:56:39




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 Re: 3 angle valve grinding?? in reply to Lil-Farmer, 11-12-2004 14:49:53  
LF,

Yep, a minimum of 1/32" wide seating surface and not over 1/16th".

Valve cooling (and it's resultant life span) depends on two things: the point at which the valve contacts the seat and the time is is allowed to remain there (read: valve lash).

A good day to ya,

Allan



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Jon H

11-12-2004 16:40:06




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 Re: 3 angle valve grinding?? in reply to Allan in NE, 11-12-2004 14:56:39  
As the others have stated,the seat needs to be wide enough to transfer enough heat to cool the valve,yet not so wide that the least bit of carbon will hold the valve off the seat and cause leakage and valve burning. We must run these old tractors on lead free gas,so if the tractor has hard seats/valves,keep the seats narrow. If the tractor has soft valves/seats,fudge to the wide side to get more wearing surface on the seat/valve face.

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Allan in NE

11-12-2004 17:00:50




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 Re: 3 angle valve grinding?? in reply to Jon H, 11-12-2004 16:40:06  
Hi Jon,

That’s what I do too, plus crowd the margin ever so slightly towards the 'head' of the valve from the center of the face.

In many applications in fact, the valve face will be ground to a 45-degree cut and will land on a seating surface cut to 46 degrees. This 1 degree of "wedging" effect will actually help in the seal as well as kinda "lock" the valve down during it's time at rest to help the cooling.

If you’ll notice, a correctly and properly ground valve/seat assembly will feel almost as though the valve is lightly “stuck” to the seat without the springs and keepers in place.

How's things going up there in the great North anyway? :>)

Allan

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Jon H

11-12-2004 19:23:07




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 Re: 3 angle valve grinding?? in reply to Allan in NE, 11-12-2004 17:00:50  
Hi Allen,
Harvest is done and all is well here. I fully agree on the 1 degree difference between seat and face angle. It makes for an instant seat up on a new valve job.



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Kendall

11-12-2004 14:13:12




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
This is usually done to high performance heads to increase the fuel/air flow into the cylinder. The radius over the edge of the valve is much smoother so air flows past it easier. The latest is a 5 angle cut. Of course to see this improvement, you need to be up in the 5000 - 6000 rpm range and are probably drag racing or doing the NASCAR thing or have a hot street rod. This would be wasted money on a tractor.

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Dick L

11-12-2004 14:00:06




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
The three angle grinding has the valve face seating on the center much narrower seat. Less area seated so supposed to be a tighter seat to hold more compression pressure. Unless you are stroking the crank, way oversizing the pistons, and putting in high domed pistons, I wouldn"t think it would do much to help these small 125 engines. In saying that, I am sure it wouldn"t hurt if the seats were done that way. I have the cutters and equipment to do it but have not on a regular valve grind. Just on special jobs for the higher compression.

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rustyfarmall

11-12-2004 13:26:54




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
3 angle valve grinding is the latest technology, and I am sure it does result in a better mating surface between the valve and the seat, so I won't degrade the theory, but I really don't think it is necessary on a slow turning engine like your B. Also, the 3 angle technology requires cutting the seat rather grinding, and takes some sophisticated equipment, (read expensive). Your old B will be just as happy with the old fashioned way of grinding valves.

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kraigWY

11-12-2004 13:26:32




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 Re: 3 angle valve grinding?? in reply to Lynn Kasdorf, 11-12-2004 13:03:22  
Your talking about seating the valves with your suction cup. There is no differance in the procedure with one, two or three angles. You are using the valves that should have be cut for the seats.



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