Technical Valves....the good....the bad....the?

Around here automotive machine shops have all but disappeared! So with a little machining background and finally finding all the tools to do valves at the Springfield Swap meet, I’m going to start doing my own!
So I’ve got a few questions that may could be answered here? Hopefully!
One thing I can’t wrap my head around is why you have to “ go back and forth “ while lapping valves in? You spin the valves to resurface them, ditto on the seats.....but you don’t when you lap?? I know they say you don’t get a true seat if you spin...why?
Also what is the best method to check to see if your guides are wore beyond tolerance?
While we’re here maybe I could get some real life experiences/opinions on “ knurling”.
Also any other help would be appreciated.






Bones

 

If ya spin the valves like with a drill centrifugal force will cause the lapping compound to be slung away from the seat. So a slow back and forth movement is required. properly ground valves and seats requite very little lapping. Knurled valve guides will work however they don't last very long. .

 

There is a lot of information in the old service manuals.
I remember seeing how they recommended to check guide clearance.
Seems like it was a wire loop around the top of the stem, and you would move the valve all the way to one side,,,zero the indicator,,and then let the valve move back the other way.
Can’t remember for sure,,,been a long time since I saw it.
The manual told the service limit for the guide before it had to be repaired or replaced.
There is always demand for a good valve man,,,,seems everyone needs you at sometime or the other.
And yes,,,there are a hundred different ways to lap the valves,,,,a little time consuming,,but worth it.
And I have seen knurled valve guides last for a very long time if done correctly.
People use too have the piston skirts knurled as well during a rebuild sometimes.
They would last fairly well too,,if the bores were not to out of round,,,,and the ring land grooves not worn excessively.
Not a racing motor for sure,,,but still very useful,,,with good power and low oil consumption to boot .

Sorry man,,,I’m preaching again,,,,lol!
Very proud of you wanting to do your own valves,,,you will appreciate all the work that goes into it.

Tommy

 

IF...one spins the valves VERY slowly, like by hand slowly, that's fine..!
Spinning by machine, (like was said) throws the lapping compound away from the seat. It also can easily damage the guide, especially if the valve and guide are dry.

As for knurling. Again, IF, you understand what's happening AND have the correct knurl tools, this can actually be of benefit.
The "standard", cheap knurl tools, not so good. Expensive properly designed tools and the knowledge of how to use them, fine.
Again, this type knurling will provide oil to the stem, but since the "upset" in the guide does not go all the way to the bottom of the guide, the...oil stops there.
I've had brand new bronze guides knurled to provide oil to a snug guide/stem, and have had very good life, with no oil leakage into the chamber, and good valve seat life.

So yea, the inexpensive method...no, the more expensive tools, and understanding how to use them, sure.

Mike

 

Almost laughable, the shortage of good (read, 'old'!) machinists!
Took some pistons in (406 FE) to an automotive machine shop here (Merced) to have the pistons "G.I.'d". Had a set of new (available) 428 rings. The owner never heard of this operation.
(the term means to have ring lands cut to fit a 'taller' ring, also {or}to install an oil spacer ring when the ring is lacking in vertical cross section for the land. A slight cut may be necessary for the latter)
We used to do this all the time in the '50s-'60s, numerous shops did this service.
(Auto Industrial, Cook's Automotive, Les Joseph's speed shop, harrington & Wilson, to name a few)
Oh, as a last resort, I called Kanter's. Counterman Bob said he'd call right back, but didn't hear from him 'til the next day.
Bob apologized for delayed call, but

1. Found a set of factory 406 rings;
2. Discounted $120 set to $90;
3. Sent them free of postage charge.

Thanks, Kanters' Bob!

 

In. The old days,,,you didn’t just throw away a set of pistons because of excessive clearance in the ring lands,,,,opened them up and added ring shims stock.
It looks kind of like a slinky.

Tommy

 

I read somewhere that spinning the valves, completely around , even slowly , would give you a pattern that could be misleading. I sure I read it somewhere, but don’t know where. Never did understand why. I even have a old machine with a hand crank on it that “ rocks” the valve back and forth for lapping a pattern.
I always lap all of my valves in. The guys at the machine shops really didn’t like the way I did things. I would take the heads in disassembled and have the valves and seats ground. I would take them back to my shop and lap each one in to check for seal and pattern and cleanliness. I think it made them do a little better job.
I learned this one time many years ago on a 300 Ford six. My Dad had showed me how to check a valve job with gasoline. So I did it and three or so valves flowed gas! I took the head apart and there was a bunch of junk/ grindings in the seat area! The intakes like that would have let all the crap in my new engine! After that..... I took my heads and valves in apart!
I also would not always do a “ valve job” on all over hauls! Got into many “ discussions “ with a lot of guys about that! Any time you grind on your valves or seats, you remove material! Make the valves thinner, more easily burnt. If the heads looked good, I would clean and lap and assemble. Just my way.





Bones

 

I do just like @Boneyard51

At work I’ll hone the cylinders new rings
Lap the valves with new seals
Everything cleaned
Disassembled the oil pump and clean it
If it’s got any signs of wear replace
I’ve knurled guides when I can take the valve and feel it rock in the guide

This is for low compression propane engines at work, never had an issue with my “ refurbished” engines
Like has been said won’t do it on a race engine.
But I’ve done this on lots of daily drivers and for customers on a budget.


The ol’ time machine shop is almost history.
Sad

 

Spent 1974 in a machine shop noted for precision. Old guy there told me lapping valves was like putting 20,000 miles on it before it starts.

 

Early 80's I worked for awhile in a machine shop that catered to the roundy racers, and everyone else in town. The only time I remember using lapping compound was to create a scuff to show you if you where out of round. And to do your 3 angle cut on the valve. It just creates a light hone on the valve. But that's just this reporters opinion..
My buddy still owns a machine shop, although a little primitive from the one we both worked in at that time. I do miss that kind of work, and the smell. Sighhhhh..

 

I like to use double sided tape and an old valve to attach to the valve I am lapping in because with used valves, the surface is often too rough to hold onto the little suction cup of a proper valve lapping tool.

When lapping the valve should be lifted a tiny bit every few seconds. This causes the lapping compound that has migrated to the outer edges of the seat to get pulled back into the working face due to its viscosity. You can always feel the increased grinding action after doing this.

 

Rarely lapped, does show up contact area a bit better ( which is minimal not the entire face btw) we cut the seats , normally new guides , new valves check the contact with engineers blue reassemble and off the car goes.

 

I have a set of 624 small block chevy heads here, that are getting the full "low buck" treatment. The valves had more stem wear than a set I pulled out of some TBI heads, so I ground the TBI valves, knurled the guides with the old tools that are chucked up in a 1/2 inch drill, did some pocket porting to them, and cleaned up the chamber edges when I relieved them around the valves. I will probably get to the seats sometime this week, but will only lap lightly to make sure everything is copacetic, and maybe even concentric. They will go on a .060 over 350 of Corvette lineage, I know it's a Vette motor, because it's been decked enough to remove the codes, and people only did that to Corvette motors. Anyway, I have ZERO dollars in the whole damn thing, so it will get the absolute shit beat out of it when done, and if it wears out quickly, I will still have learned something, and had fun also. I also have 3/8ths knurling tools, so some big block Ford D2's are next on the list. I'll let you know how that goes. Big block Ford, or FE, same thing to me.

 

Well... lapping is mainly utilized to show the condition of the seat. Not so much to improve
the seating, but that does happen! It mainly is a double check to see if everything it ok! Height and width of the seat, unless you lap, it is a guess!
If your old machinist says it puts 20, 000 miles on a valve job...... maybe you need to change shops. ......Just saying....




Bones

 

Even with the 3-angle valve job and interference angles between the valve and seat, I still prefer to blue 'em up and lap them in. It has been a long time since I did one, on a '48 Plymouth for a guy at work. We had an old timer come in and do the seats and valves, wanted an extra $10 to lap the valves in... gave us a few pointers so we did it.

 

One common mistake made when knurling is not getting the grit cleaned out after running the first knurling tool through. It doesn't cut threads, it forces through, raising the surface. The cast iron tends to crumble leaving grit behind. It needs to be throughly cleaned (with guide brushes in a solvent tank)before the burnishing tool is run through. Anything left in the guide will be trapped when the burnishing tool is run through. Then another cleaning after burnishing.

The good knurling tools use a burnishing tool, not a reamer. It takes a oil and effort to push the burnishing tool through. It is tempting to shoot a reamer through but it won't last if you do. Get or make some good head stands.

 

Back in the 60s I worked in an auto machine shop doing heads. A lot of heads came from the Olds dealer that came from the factory knurled and I replaced the guides not a fan of knurling guides wear at the top because of the rocker pushing side ways on them. As for laping I just never do it Slap the valve against the seat and look at the impression. If it looks OK go with it. I try for .060 wide intake and .090 exhaust seats. Most of all clean them again before assembly. You would be surprised how many come back from the machine shop with grinder grit in the ports. Same goes for passages in crank after ground.

 

A three angle valve job is beyond the skill of many machinist.

 

The reason you lap back and forth a few times then raise the valve off the seat is 2 fold. First, if you spun the valve 360° and the head was bent at all, all you would get is that single high spot making the lap marks against the seat. By only lapping a short distance you will get a better idea of the overall condition of the interface. Second, as mentioned above, when you lift the valve off the seat it pulls the compound back into the lapped area.

 

Use to knurling a lot of valve guides back in the days, remember using STP for lube when doing that.
One trick when grinding valve seats, I use a black sharpie and make 4 wide lines running across the seat then when I use a top and bottom cut to narrow the seat you can tell how wide the seat is. If that makes sense.

 

On a 45 degree seat a 30 degree top cut and a 60 degree bottom that how you get the seat width you want.

 

^^^ and go real easy on both of these cuts. I have had the 60 degree stones explode on me before.

 

Steve if you slap the valve against the seat you can see an impression on the valve if you want to see it better spray a light coat of dry graphite lube on the valve before you slap it. Lapping compound is pretty much grease and fine grit and hard to get rid of. And I agree with salt flats just let the weight of the stone do the work.

 

Gotcha, Paul, but I don’t see as good as I used to. I watched the machine shop boys do this. And I know for them time is money and they do what they have to do. A job that would take them two hours will take me two days...... but I’m retired and time means nothing to me anymore! Lol and I like to play with my tools. I am a clean freak when it comes to my engines, a thing my Dad taught me. That is why I was so furious when I found all junk in my six cylinder head, years ago. In my years I have found many errors in valve jobs that I paid money to be done right. Once you bolt the heads on it hard to determine if you have a leaky valve and even harder to correct. I’m not recommending anyone do what I’m doing, I’m just doing this because I want to. Probably won’t work in a commercial setting.....but can always use pointers!






Bones

 

I was working at a Ford dealer in the '60's. Someone bought a shiny new guide knurling tool to try out. The best mechanic in the shop gave it a try on a customer job and snapped the knurler off in the guide. First and last knurling job for that shop.

 

It all goes back to cleaning your work.
Most people don’t go the extra effort to make certain that all the junk is out .
As someone said,,,I always take my heads disassembled,,,,head castings and valves.
Then I lap all the valves and make certain that I have a good seat marking.
Then I reclean all the valves and seats. I number each valve to what chamber it is for also.
It is very easy to clean,,,just some more effort.
But,,,I have never had a valve leak since I started this process.
I did before,,,but not now!

Tommy

 

Just let the machine shop assemble them with their guarantee, then take a look see yourself.

 

That’s the way I do it! While I don’t have all the machines to do all of the machining on an engine, I do have the tools to check what machining was done. I never “ trust” a machine shop.....I always double check before assembly, mostly because I don’t want to do the job again! And want to avoid the finger pointing if something isn’t right when the engine is started.






Bones

 

Ive pretty much weaned myself away from machine shops. Just not worth the hassell and money it cost. Ive got valve grinding equiptment. someday I will happen on a boring bar at a bargian. Until I do its gonna be ring and hone jobs on used engines.

 

I’ve got a boring bar, that I have never used..... I think the motor is toast. I think in a Van Norman or something like that.....got anything to trade?





Bones