To make sure the valves seat right:

Before we begin:
**Install the valves back to its original position (don't mix them up)**
1) Put some talcum powder on the valve seats.
2) Lightly tap the valve back to the head.
3) Check the powder for full contact on the valve face.
My ghetto procedure to double check for leakage:
4) With valve springs and retainer installed, fill up each port with Draino.
5) Leave the head overnight and see how much Draino being seeped through.

Set,

Originally posted by sonicnofadz
Hey suparata, lets say someone took the valves from above, and tried to take a feeler gauge between the valves and the valve seat (while properly installed). If there was no gap (or at least an extremely tight clearance) according to the feeler gauge, would you say it would be safe to run the valves without modification? I'm not a machinist so I don't really know if a feeler gauge would be the right way to measure this sort of thing. If not, how do machine shops determine if the valves are indeed sealing properly against the seats? What kind of instruments do they use to measure this? While my cylinder head was at the shop I didn't get a chance to watch the machinist do much of anything, I was too busy getting my car ready for the re-installation of the head.

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Wtf is "talcum powder"?

white stuff that puts on diaper.

Originally posted by sonicnofadz
Wtf is "talcum powder"?

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most machine shops use machinist's dykem, a liquid dye.

And kerosene, not Drano.

How bizarre.

And no, you can't measure valve contact with a tool.

i figured if it's strong enough to cut through clotted sinks, it should be good enough to find leaks on heads.

Originally posted by Defiant
And kerosene, not Drano.

How bizarre.

And no, you can't measure valve contact with a tool.

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Originally posted by BISHILVR
most machine shops use machinist's dykem, a liquid dye.

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The shops I have been to use a vaccum tester...they place it over the exhaust port, the intake port, and over all four at once. It is a very fast, simple, and reliable process, I wouldn't use a shop that did not have access to a vaccum test.

Mike

Originally posted by 90AWDRaleigh
The shops I have been to use a vaccum tester...they place it over the exhaust port, the intake port, and over all four at once. It is a very fast, simple, and reliable process, I wouldn't use a shop that did not have access to a vaccum test.

Mike

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Sure, you guys and your twentieth-century tricks.

If you ever need vacuum, get an empty refrigerant or propane tank, whatever fittings you need, and suck it down with manifold vacuum. Then you can hook it up to whatever you need to test, and not have any background noise.

Originally posted by Defiant
not have any background noise.

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Machine shops actually have guages to measure the vaccum, they don't go by sound.

One things for sure: guys are ingenious when it comes to diagnosing things.
You guys are making me work extra here to take pictures hoping that it will make things clearer.
So here it goes.Pictures here will hopefully help http://www.engintecs.com/gallery/album11
We've been through what happens after miles and miles of engine operation : pitted valves http://www.engintecs.com/gallery/album11/Exh_valves2 , pitted, wide and out of concentricity valve seats http://www.engintecs.com/gallery/album11/Wide_seats_and_starting_to_loose_the_seal all these resulting in bad sealing and cooling of the valves. While some believe that by just lapping the valves they will solve the problem http://www.engintecs.com/gallery/album11/Just_lapping that is not true: all they accomplish is even wider seats http://www.engintecs.com/gallery/album11/Just_Lapped_vs_Reconditioned that will seal for a while but the increase in surface means a decrease in seat pressure which will eventually lead to a valve failure http://www.engintecs.com/gallery/album11/Result_of_bad_sealing2 . Never mind the fact that by just lapping they will not correct the concentricity problems so it's really just a waste of everybody's time an money.

Vacuum gauges are a good way to make a final check after all the machining and measurements are done . While they are good to diagnose something really bad they won't tell how bad things are (I've pulled decent vacuum on heads with bent valves). That's what concentricity gauges are for http://www.engintecs.com/gallery/album11/Seat_runout2 . Also Prussian Blue or Machinist Blue or whatever you want to call it will give you an idea of how wide the seat is and where it is located on the face of the valve but because of other tolerances involved especially if the guides are loose it won't give you an accurate "reading" .

Over night leak is not a bad idea but how do you measure that ? What is considered acceptable and what not? And as one can see in the pictures valves can be made to seal enough for a while but for how long that is?

Bottom line you have to leave things to your machinist and if you don't trust your machinist than you shouldn't be there from the beginning. He is the only one who can assess the damages and have things repaired right.

Mitch.

Mitch,

Thanks for the detailed info. My method to locate which valve leaks the most is kind of vague. However, this will roughly point you to the right direction especially if you want to do everything at home. In my case, I want to get away as cheaply as possible without tearing it part again after 10 miles travel down the road. Granted the shortblock will need a rebuild pretty soon because of blowby's. Good luck.

So hold on, lapping the valves to sit properly is not the best method/total package? My valves previously were set bad, I guess, because one of them ended up like some of those pics, with a chunk missing out of it. We purchased new exhaust valves, then lapped them. The intake valves we just lapped. The residue on the head of the valves we just scraped off with a paint scraper. It seemed to work? I don't know, all this talk has made me almost want to check out those valves again.
Oh my dad is a die hard DIY guy, so there was basically no chance of a shop doing it... Apparently his methods work because he has a 1975 Volkswagen Rabbit still running which isn't too old... only 29 years. He had to do the exact same job to his Rabbit so I figured it should work.
Brian

Think about what it has to be done when reconditioning the head and what you accomplished by what you did . All you have to do is look at the pictures to understand.
If you had a burned valve you had at least that seat and guide damaged too .
You did not tell us how much oil is your Dad using. If you are telling me that the Rabbit did not have the guides shot is either because it had very low mileage or you have to contact Guiness Book since your Dad has the first VW that is not as hard on the guides as all the rest of them are out there.
Mitch

It has 165K miles on it, less than my car... How much oil, I don't exactly know what you mean. He coated the valve stem in oil so it slides smoothly in and out of the guide, and he uses a regular amount when changing it.
Brian

Do you have an inferiority complex? Your opinions on how someone decides to do a "budget rebuild" are ridiculous. Guess what? I just pulled the head off my car to replace the head gasket. I reused the timing belt. Now you can tell me that I will do everything in life half ass. This guy asked a simple question on a DSM forum. Your not his freaking dad. Your are ###!

Originally posted by Suparata
You think you are helping him with your input and guess what: you are . You teach him HOW NOT TO DO THINGS. The difference between you and him is that he knows he made an honest mistake and he is willing to learn how to do it right and you are not. So you did a shitty job on your head to "save" money but does that make it right? HELL NO !!! The problem is that even after you did it you don't realize that what you did was wrong and you're trying to share your "experience" with others. Nobody is "bashing" him for not spending money and even though I jumped on him at the beginning of this thread , he did not feel insulted and he showed the willingness to learn which he did. Did you?. It is not about how much money gets spent , it is about how to do it right. Besides giving you great satisfaction DSM's also give you the opportunity to learn a lot especially how to approach things in life : put your hearth in what you are doing and you will be rewarded. Even if other things go bad on you , you can still wake up every morning and look in the mirror without being ashamed of what you see in there. You are going to approach things in life just the way you are approaching the work on your DSM. They were designed with this concept in mind. The designers knew that in ten years there will be an army of young warriors that will need to find their way in life and need to learn that it is not the "Easy Street" who will take them at the destination.

This was deep wasn't it?

Mitch.

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Originally posted by forcefed98gst
Do you have an inferiority complex? Your opinions on how someone decides to do a "budget rebuild" are ridiculous. Guess what? I just pulled the head off my car to replace the head gasket. I reused the timing belt. Now you can tell me that I will do everything in life half ass.

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(You'll notice I never mentioned surfacing a head that'd blown a gasket with a mill file [It's _still_ holding]).

However, once you _have_ had the opportunity to build a motor the "right" way all the way through, it'll spoil you.

Originally posted by 19Eclipse90
It has 165K miles on it, less than my car... How much oil, I don't exactly know what you mean. He coated the valve stem in oil so it slides smoothly in and out of the guide, and he uses a regular amount when changing it.
Brian

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What I meant was how bad is the oil consumption. VW are among the toughest on valve guides out there. They have tiny little guides (short) which wear out like crazy resulting in a bad metering of the oil that goes down the guide, insufficient cooling of the stem and allowing the valve to move all over the place but right. That is bad when the engine is running but is "good"(if you can say that) when somebody is lapping them because it will leave a lapping mark everywhere on the seat no matter how much the seat is off.
I maybe a little tough when it comes to so called "budget rebuilds" but that is because what that means is usually a shitty job and I respect engines so much more than that. I believe that if I treat an engine right it will only give me satisfaction.
I'm also trying to back up what I'm saying with examples that can explain how things work so who ever is willing to learn something can do that. That's why I took the extra time to take some pictures and made this sub-album
Just take a good look at the pictures and their titles and you will understand what I'm talking about.
Mitch.

Originally posted by forcefed98gst
Do you have an inferiority complex? Your opinions on how someone decides to do a "budget rebuild" are ridiculous. Guess what? I just pulled the head off my car to replace the head gasket. I reused the timing belt. Now you can tell me that I will do everything in life half ass. This guy asked a simple question on a DSM forum. Your not his freaking dad. Your are ###!

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I don't know what to tell you because you are so out of line. Not only you lost your sense of humor but apparently the only thing that has been said here that caught your eyes and triggered you was a post that was the cold truth softened in funny way of saying it.
You've decided to be a spokesman for somebody who did not ask you to be and I don't know why. Is it because you are proud of the corners you've cut? We all learn interesting things here. Are you?
You had the privilege to learn things that most out there don't have the chance just by filtering what has been said and look at a few pictures .
I just hope that I will have the chance of knowledgeable guys out there taking the time to tell me when I'm wrong and clarify why I'm wrong and what should I do.
Let's end this argument here and get back to what this forum is supposed to be: a place open for peolpe to learn things.
Thanks
Mitch.

Mitch, I'd like to thank you for all the pictures and the time and effort you have put into helping all of us who are willing to learn something. Unfortunately, for my simple self, I still don't see the difference between just lapping and the whole reconditioning. The whole reconditiong looks to be cleaner, but I don't think that's just it, I mean I cleaned all I could, but whatever more there is to it, please, go ahead---
Brian

Originally posted by 19Eclipse90
Mitch, I'd like to thank you for all the pictures and the time and effort you have put into helping all of us who are willing to learn something. Unfortunately, for my simple self, I still don't see the difference between just lapping and the whole reconditioning. The whole reconditiong looks to be cleaner, but I don't think that's just it, I mean I cleaned all I could, but whatever more there is to it, please, go ahead---
Brian

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Like I said after so many hours of operation and millions of times the valves pounding the seats under high heat conditions the seats get wider than they are supposed to be. They also get pitted and loose their concentricity to the centerline of the guide. Same thing happens to the face of the valves. By lapping the valves you only make things worst because what happens is that the seats get even wider and, even though the immediate result is better sealing than before you started, the increase of the width of the seat yields a decrease in seat pressure(the pressure that the valve applies on the seat) which in time means loss of sealing capability. Not to mention that by lapping you will not address the concentricity issue.
When both seats and valves are machined the results are two smooth, clean, concentric and the right size surfaces that will seal well for a long time, will provide adequate cooling of the valves and will not put a constant strain on valves and guides like seats, valves and guides that are not concentric to each other would do.
If I could only be able to say what I think more clearly.
Mitch.

I just came across this link , this link and this one that might be interesting for you guys.


This one might make things easyer to understand.
Mitch.

This thread has turned around from a flaming contest, into a very informative and detailed thread. I've learned many things.

I could use some input. I picked up a AWD project car for 800 bucks. I have pulled the motor and engine specs are checking out good so far, but the head is in bad shape. All of the intake valve guides are cracked, and the exhaust valves guides have enough play be scary. (valves must have been bouncing around pretty good while running)
Ended up with a couple burnt up valves with two very wore seats.

My question is that if the seats are wore beond regrinding at a machine shop, am I going to run into a lot of machine time and money to replace seats and guides. I know shop fees vary, but I would just like any estimates from people who have had quite a bit of machine work done. Or should I look at a good rebuilt head from somewhere else.

I am taking the head to the machine shop later this week.

Again, Props on all the good input in this thread. Keep it up. A good valve trane is what makes or breaks this DOHC cars.

Thanks,
Frontwheeler

mitch will prolly love this, but its my experience so i'll say it, when i blew my head gasket and had to remove my valves to get the head shaved. i looked at the valve seats and noticed some pitting (132k) so i decided to regrind the seats myself.... using valve grinding compound and my hands to spin the valve took a long ass time but i got the seats to a point where i was happy to think i wouldn't ever burn a valve. so far i've put 15k on the car and no problems yet... but did i make things worse here if i "reground" them and had sloppy valve seats? i put new seals in and noticed my oil consumption went down alot due to the fact it used to smoke when it idled for awhile. o well whast done is done it worked fine for me so far,......
Ryan

did everyone forget what draino and alum does?

I work at an engine remanufacturing facility, head shop in particular, and everything the supra guy has said is good advice.

When you DIY, no matter what, you're just delaying the inevitable.

You do not have to have a valve as a reference to cutting the seats, though.
Mistubishi heads use a 44 degree angle on the seats and valves.
All we do is just take the special drill press (forgot what its called), and usually cut about .050 off of the seat surface. That much will usually clean a seat up unelss it's fubar'd. If your seat is cracked or crooked, all they do is just press a new seat in and cut it to within spec of the rest of the seats.
Whenever they cut seats, they cut .020 off of the seat with the biggest margin, and cut the rest to match the deepest seat.
Also, whenever we recondition the valves, we use a "Valve grinder". Its a fine grinding stone with which you can set the angle. I would never EVER EVER EVER put a valve in a head without having it ground. The slightest imperfection will cause the valve not to seal in the seat.
For the guides, you can use the stock guides in any head unless they are damaged.
We have this neat little mini borescope that they use to measure the size of the bore on the guides. We also have this little drill press that bores out the valve guides if they need it. After they're bored, they get guide liners pressed in to where they are within stock specs. That's the correct alternative to putting in new guides. The liners don't wear out as quick as the guides themselves do (you will have a worn out guide quicker than you will have a worn out guide liner).

I don't care what head shop you work at, they all use the same thing to help seal the valves. The only real way to check a seal is through a vacuum checker. You can tap the valve a few hard times in the seat and look at the contact surface, but there are sometimes imperfections that the eye can not see in the ring. All you do is place the head on a rubber mat, and stick the vacuum hose (with a nipple on the end) in the spark plug hole. A good reference number is at about 25 inches of vacuum. Anything less will result in low compression numbers on an engine. If the chamber does not seal up, you take the nipple (with an adapter plate) and check each of the intake and exhaust runners.


Basically, the point i'm trying to make is that if you DIY your head rebuild, you won't have a "new" head. The only way to get your head into spec is to have a machine shop do it. They have special tools that no one else has which are almost required for precision checking. Everything i said is based on experience. I've been building heads every day for the past 1 and a half years.
You might be on a budget, but like i said above, you're just delaying the inevitable.

(this is all in my opinion, though.. before getting the job at this shop, i would have just treid it myself.. but after being on the inside and basiaclly eating, sleeping, and dreaming headwork, i wouldn't do it any other way.)