3 angle valve job tech question

[m_0ney_pit]

So I had a 3 angle valve job done to my 1g head to freshen things up. I had lapped the original factory 3 angle cut with new stainless steel valves (engnblr) and did not like the results because although there was a solid line around the entire valve and seat it varied for each valve and seat. I'm geussing the seats were pretty rounded.

After the fresh 3 angle job I relapped the valves and have a nice thick solid line all the way around that is exactly the same for each valve/seat combo.

My question is, the angle furthest on the outside of the seat has a dark gray line while the 2nd and 3rd look shiney and new like they were cut. Everything seals up perfect and holds pressure without leaking at room temperature.


So got some questions:
1. So what will happen when the head is at operating temperature and whats the purpose of the 3 angles in the first place? Do the 2nd and 3rd angle get used as the head heats up?

2. I was told that the abrasive from the lapping job can shorten the seat and valve life, is that true?

 

[RWD4G63]

1. Three angle valve jobs make the head flow air better. The 3 angles are to help the air/fuel charge transition from the port into the combustion chamber. The first and third angle will never contact the valve.

2. I don't know about shortening valve life, but lapping is not needed with proper, accurate machining.

 

[m_0ney_pit]

1. Three angle valve jobs make the head flow air better. The 3 angles are to help the air/fuel charge transition from the port into the combustion chamber. The second and third angle will never contact the valve.

2. I don't know about shortening valve life, but lapping is not needed with proper, accurate machining.

Ok got it, I read that a few times that a fresh 3 angle doesnt need to be lapped. I told the machinist that I lapped the valves and he freaked out and told me if I would have run the head it would have sealed. Dony know if I buy that.

 

[RWD4G63]

I should correct myself. The First and Third angles won't see valve contact. The Second angle should be the valve seat.

 

[m_0ney_pit]

I should correct myself. The First and Third angles won't see valve contact. The Second angle should be the valve seat.

So since the lap ring is on the first angle at room temp you think it will give me sn issue?

 

[BogusSVO]

http://www.dsmtuners.com/forums/newbie-forum/453196-question-bogussvo.html#post153155350

read posts #27 and 30

Sounds like the machinist may have used a 4 angle cutter, but only hit with 3 of them.


It would go 45* (seat) 60* bottom, 70*-80* throat

You are missing the top angle of 30* or it is so narrow you are just not seeing it.

The 45* seat seals against the 44*-45* valve face angle.

Just like RWD4G63 said, the rest of the angles are for controlling air flow past the seat.

The only angle that will ever contact the valve is the 45*

No matter if it is 3 angles or 10 angles

 

[m_0ney_pit]

http://www.dsmtuners.com/forums/newbie-forum/453196-question-bogussvo.html#post153155350

read posts #27 and 30

Sounds like the machinist may have used a 4 angle cutter, but only hit with 3 of them.


It would go 45* (seat) 60* bottom, 70*-80* throat

You are missing the top angle of 30* or it is so narrow you are just not seeing it.

The 45* seat seals against the 44*-45* valve face angle.

Just like RWD4G63 said, the rest of the angles are for controlling air flow past the seat.

The only angle that will ever contact the valve is the 45*

No matter if it is 3 angles or 10 angles

Well since the lapped ring is so thick (3mm)im guessing I must have 45 degree valve to seat contact and not 45 to some other seat angle.looking at the seat again it looks like the is another angle on the outermost on the seat that is still shiney.

Is it a problem running the seat to valve contact so close to the outside of the seat?

Also, after lapping with the permatex compound the surface roughness looks really high, I would assume for good sealing you would want a low surface roughness is this correct?

 

[BogusSVO]

As long as the valve seals is all that matters.

If you "dry" lap, use no compound, just spin the valves again, it should smooth out.

 

[turbo23]

There are a ton of things that go into a 3 angle valve job. Normally the middle angle is a prefect 45* angle that matches the valves 45* angle. The top and bottom are what make the valve job important. You can change the angles and affect how the valve flows at different lifts. We use low lift cutters on 4g63 heads because in general we have pretty low lift numbers(4 valve head). Also setting the cutter up so the valve touches the seat as far out on the valve as possible while leaving a (finger nail size)small untouched ring just outside the lap ring. Doing this essentially makes the valve bigger.

If you are running 1mm oversize valves our seats are not actually big enough to promote a top angle and it is normally cut into the aluminum of the head if the seats are slightly sunk into the head. If the seats protrude from the head then you might not get that third angle without dropping the valves which will then require install height changes so your springs work like they should. You should post some pictures for more help but regardless I think you will be fine.

 

[m_0ney_pit]

I remember him saying that he was going to do a custom angle to make it flow better so thats probably it, sorry I'm a newb with machine work. So I'm pretty sure I don't want to leave the valve and seat as they are after lapping with the off the shelf permatex material so I think I'm going to lap with some finer abrasives. Thinking I'll do a 3um paste then finish with a 1um.

I'll post some pictures tomorrow when I get back from the garage.

 

[BogusSVO]

Colgate toothpaste for the finest abrasive.

 

[m_0ney_pit]

After doing alittle closer looking at my seats it seems that there is 4 faces, a super thin on the outside, the valve to seat contact and 2 interior angles.

Just wanted to show the before and after grinding with some 3um SiC and 1um Diamond pastes. I'll probably finish up with some 100nm alumina paste.

I will never use the permatex grinding compound ever again, its apparently made of glass type abrasive and imbeds small shards of glass into the seat and the valve face. If you don't get this stuff out, I could see it coming out gradually as the engine is run and leaving pits behind with will mess up the sealing. I had to clean the valve and seat completely after the first pass with the 3um because the shards of glass become unlodged.

Left is after grinding with peratex, right is after SiC,Diamond polish.

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[JacksonAuto]

The 45* on the valve doesn't look quite right.

Also, in the last pic the valve on the right looks funny. Is it bent? Note the irregular pattern on the top angle. Or are they just cheap valves?

 

[m_0ney_pit]

The 45* on the valve doesn't look quite right.

Also, in the last pic the valve on the right looks funny. Is it bent? Note the irregular pattern on the top angle. Or are they just cheap valves?

Why do you say the 45 doesnt look quite right? Ill check with a caliper to see if the length of the polished 45 degree angle on the valve matches the width of the 45 on the valve seat.

The valves are engblr from ebay, I spun them with a drill and cant see any deflection so I would assume this one is not bent to a degree that would affect anything.

 

[BogusSVO]

Jam, Looks like a "domestic" blade was used to me, around a .060 wide seat?

I think the pic is eyeball screwed, if the valve was really bent as much as it looks, there would not be a contact patch on half the valve.

 

[JacksonAuto]

On the valve, the 45* looks very faint and it isn't even all the way across. Note the shiny spot in the middle of the 45. It's more evident in the first photo. Look at the valve on the left. In the last photo, the top edge of the 45 is darker than the bottom. This means the angle on the valve and the angle on the seat aren't precisely the same. I'd dress the stone and grind the valve to get them to match and then re-lap them.

As for the runout, you're not going to see a couple thousandths by using a drill.

 

[m_0ney_pit]

On the valve, the 45* looks very faint and it isn't even all the way across. Note the shiny spot in the middle of the 45. It's more evident in the first photo. Look at the valve on the left. In the last photo, the top edge of the 45 is darker than the bottom. This means the angle on the valve and the angle on the seat aren't precisely the same. I'd dress the stone and grind the valve to get them to match and then re-lap them.

As for the runout, you're not going to see a couple thousandths by using a drill.

I think that it looks darker towards the top of the valve because of the first lap job on yhe OEM seat cut being in a different spot than the current 45. When I checked the valve with a drill I chucked it up and checked with a razorblade that was held stationary to the table(think ghetto lathe). I think in microns but it didnt seem to vary by even a mil.

 

[JacksonAuto]

The inconsistency is present on the seat, too....

 

[m_0ney_pit]

It looks like the ring at the top is leftover permatex grinding material and the inconsistency is a 5 to 10um groove carved by the compound. I kind of want to call them and complain about what a terrible product this is.

 

[arrowhead]

Well valve margin is what we are talking about here I guess.

First there is nothing wrong with using Permatex to lap your valves, either water or oil base, nowdays with superior tools is not really necessary although I personally like to give them a touch.

I like to go with the interference angle to make sure it seals from the first start.

Valve margins are going to vary depending on engine usage, remember that is the point of heat transfer to the head, on a drag engine a narrow margin will work fine but for the street or an enduro engine a wider margin is recommended.

Some of the valve patterns are not equal, you may have a problem with some of the seats

 

[m_0ney_pit]

well we are just going to have to dissagree on this one, from what I have seen the product embeds glass particulate into both the the valve and seat that can only be removed by grinding with another compound. So if you like glass embedded into your parts by all means go ahead and use it.

 

[BogusSVO]

well we are just going to have to dissagree on this one, from what I have seen the product embeds glass particulate into both the the valve and seat that can only be removed by grinding with another compound. So if you like glass embedded into your parts by all means go ahead and use it.

It is fine you disagree with the permatex valve lapping compound, it has only been in use for what? 30? 40? 50? or more years.

You are the first, last and only person I heard had an issue with it.
Also, I would not want to hazard a guess how many gallons of the stuff is used yearly.

Does it embed in the seat and valve? Yes it sure does. How else are you going to see the lap line?

Is it going to cause damage to valve and seat, I do not think so, and I have never seen anything to suggest it has.

IMHO, it just turns to microscopic dust particles once the heat from combustion is added and the valve pops on the seat a few times and out the exhaust it goes.

Also the drill method you use is about the worse way to lap a valve, Here again IMHO, due to valve guide clearance, the valve can #### and you can wear one side of the seat more than the other, leaving the seat oval, and not round. Plus you no longer a flat seating surface on the valve, but a concave face on the valve.

 

[91-GS]

If a drill is not good, what about a mechanical lapping tool that spins 3/4 rotation one way and 1/4 or so the other?

 

[JacksonAuto]

If a drill is not good, what about a mechanical lapping tool that spins 3/4 rotation one way and 1/4 or so the other?

A lapping tool or drill are not a substitute for a valve grinding machine. You want accuracy.

 

[BogusSVO]

A lapping tool or drill are not a substitute for a valve grinding machine. You want accuracy.

This is true, also you want seats cut, not ground.


If you are lapping the valve for more than checking seat contact, then you have other issues.

A simple hand spin stick with a suction cup is all that is needed, Also if you have to hand lap a valve for more than maybe 10 seconds, the head needs to be checked out by a machine shop.

http://www.dsmtuners.com/forums/articles-engine-fuel/341636-how-lap-valve.html