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 Post Posted: Fri May 25, 2012 8:39 pm 
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do you lap the final valve job, or, for a double check of seating is doing so acceptable?

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 Post Posted: Fri May 25, 2012 9:05 pm 
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Engineer bluing the valve seat is more important, it shows if the seal is going to be there without placing bending stress in the valve. Lapping will still happen with a bent valve etc. Lapping a good seat is important, as the seats from the machines are not as good as a lapped seat. A poor operator doing a machined lapped seat is not as good as a poor operator doing a paste hand lapped seat. All seats need to be checked with kerosene for leaks.


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 Post Posted: Fri May 25, 2012 11:08 pm 
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Larry Woodfin wrote:
do you lap the final valve job, or, for a double check of seating is doing so acceptable?

I like to lap the final vj, not so much to check that it seals (I don't think it shows that) but I think it is a better finish and it is a good visual for where it is contacting.

Rick


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 Post Posted: Sun Jun 03, 2012 7:53 am 
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When I got the heads I have now I lapped the valves just a bit to see how they were seating. I didn't do much, just a touch, but it showed me what I wanted to see. They were pretty much perfect!

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 Post Posted: Sun Jun 03, 2012 10:38 am 
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There are some shops that would not think of lapping a valve. I think Larry Meaux is one of those that uses a Bridgeport to do valve jobs and on his last cut he turns the cutter by hand. The seat is perfectly smooth, unlike the surface that lapping leaves. Here's a quote from Chad Speier on DRR

Why would I want to sharpen my cutter every 3rd seat, dial it in with proper spindle rpm, and be as precise as I can be, and then use grit on my perfectly machined seat? That makes no sense to me!

However, I've seen some stuff run really fast with leaky seats..

I've done it on heads that just can't be valve jobbed anymore, like Comp or Super Stock heads. Much like what I did to Paul's deck. However it's not to find the seat, it's to make sure the seat hasn't moved..

Many ways to skin a cat. What works for you... well works..


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 Post Posted: Sun Jun 03, 2012 10:39 am 
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There are some shops that would not think of lapping a valve. I think Larry Meaux is one of those that uses a Bridgeport to do valve jobs and on his last cut he turns the cutter by hand. The seat is perfectly smooth, unlike the surface that lapping leaves. Here's a quote from Chad Speier on DRR

Why would I want to sharpen my cutter every 3rd seat, dial it in with proper spindle rpm, and be as precise as I can be, and then use grit on my perfectly machined seat? That makes no sense to me!

However, I've seen some stuff run really fast with leaky seats..

I've done it on heads that just can't be valve jobbed anymore, like Comp or Super Stock heads. Much like what I did to Paul's deck. However it's not to find the seat, it's to make sure the seat hasn't moved..

Many ways to skin a cat. What works for you... well works..


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 Post Posted: Sun Jun 03, 2012 2:18 pm 
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I'm sure if you saw a seat after a cutter was done with it under a microscope you'd think it was done with a hammer and chisel. There is no perfect seat, only "good enough". Anybody who thinks their seat is perfect isn't looking close enough.

I think it was Darin Morgan that made a comment about lapping valves on a forum saying why would he use rocks on his seats after he'd used his nice cutters on them, rocks can only make them rougher. whatever....

Well, you shine and polish your car with "rocks", they polish diamonds with rocks. Everything is polished with rocks of one size or another. Industrial valves that must seal very well (much tighter seal than a race engine) are lapped.

The real question is can a cutter make a seat "good enough" or can lapping make a seat "good enough"? Yes, I think either can be good enough.

Rick


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 Post Posted: Sun Jun 03, 2012 8:10 pm 
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Being an Industrial Maintenance Machinist with Va State Journeyman's certs most of my working career, I've seen machined finishes under a microscope and "it ain't pretty"!! Anything except a ground surface looks like s**t! A really "fine" lapping compound leaves a better looking finish under a microscope than any machine tool does. Just depends on how small the "rocks" are! ;-)

And on another note. I worked as an instructor in both the Nuclear and Coal fired power plant fields training mechanics on how to resurface valves used in both Nuke and Coal fired plants and EVERY process that was recommended to refinish those valve seats was basically a lapped finish!

I lap mine! ;-)

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 Post Posted: Sun Jun 03, 2012 8:54 pm 
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I guess it wasn't Larry that told me he didn't lap. Here's his quote on lapping.

"yes , always just as a double-check
i use Red Dye on Seats and Valves , then Lap,
the Customers like to see the Lap Line"


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 Post Posted: Sun Jun 03, 2012 9:00 pm 
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Ron Gusack wrote:
I guess it wasn't Larry that told me he didn't lap. Here's his quote on lapping.

"yes , always just as a double-check
i use Red Dye on Seats and Valves , then Lap,
the Customers like to see the Lap Line"


Yeah, that's what I'm talking about. BTW, those valves at some super heated coal fired power plants see 3,000 psig at the seat! Think your BBC or SBC will generate THAT kind of pressure? =;

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 Post Posted: Sun Jun 03, 2012 11:05 pm 
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Ken0069 wrote:
BTW, those valves at some super heated coal fired power plants see 3,000 psig at the seat! Think your BBC or SBC will generate THAT kind of pressure? =;

Our new coal plant (940MW supercritical) runs above 3600psi main steam pressure and 1080ºF at the turbine at full load so the feed pump discharge pressure is > 4000psi. O:)

Rick


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 Post Posted: Sun Jun 03, 2012 11:17 pm 
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rick360 wrote:
Ken0069 wrote:
BTW, those valves at some super heated coal fired power plants see 3,000 psig at the seat! Think your BBC or SBC will generate THAT kind of pressure? =;

Our new coal plant (940MW supercritical) runs above 3600psi main steam pressure and 1080ºF at the turbine at full load so the feed pump discharge pressure is > 4000psi. O:)

Rick


If memory serves, most nuke plants seldom see over 1500psig on the secondary side (turbine) and most of the time that is saturated steam. B&W OTSG nuke steam generators are the only nuke plant steam generators that will produce "super heated" steam. Primary side on a nuke plant is usually up around 2250psig with borated water up around 605*F.

FYI, when the guys that I trained at that 3,000psig coal fired plant down in Lake Charles, La went looking for steam leaks at pipe joints and valves they use broom sticks because that dry high pressure steam will cut a hand OFF, in a New York minute!

Some really dangerous stuff out there the people work around EVERY DAY.

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 Post Posted: Wed Jun 13, 2012 11:53 am 
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Larry
I know this subject is quite old but I would luv to give you an opinion. Some one above stated about using gravel or glass to smooth out seats. I have been a Mechanical Engineer for more years than many people are old. Ther has not been much that we in our engineering group hasnt studied. Lapping parts was one of the studies that we did a Six Sigma project on. I was a Black belt Six Sigma and was teaching the class and this subject came up. So we studied. We did as some one above said, used a microscope to look at before we lapped and after. We found that most all surfaces did not get a clean cup, no matter how we cut it. It always appeared to be torn and it would lay over the metal. If we assembled the 2 mating parts, it would pound the metal over and down on itself and then later come loose and embed into the seat or in the valve or just fall out leaving a small void in the seat sometimes leaving a not so impressive seat. We then went to using a brass brush turning backward to break loose and remove the torn material. We then found if we lapped using a material from a company called Timesaver. It was guaranteed not to continue cutting. We would lap for a few seconds and it improved the finish and then stopped cutting. It also was guaranteed not to imbed in metals. They had several varieties but the one we settled on was an abrasive made for cast iron and steel with NO imbeddability. I still use it to day in my automotive machine shop and my machinist machine shop. I would never consider letting two mating parts go out without knowing they seal on a smooth surface and not on folded over metal. We also found to tap each part a couple times against each other improved their surfacing. At that time we were doing over 100,000 seats per week. Our failure and recall rate of approx 1% went to virtually zero. This is different if you are using a single point cutting tool(Newen).
Just my opinion for what it is worth
reed

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 Post Posted: Wed Jun 13, 2012 2:18 pm 
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webermaniac wrote:
Was the compound one of these?

TIMESAVER LAPPING COMPOUNDS



Yes it was a compound from Timesaver. I just looked at that website and it is exactly what I have at my shop. It breaks down very quickly, mixes with oil so that you can get the consistency that you want. It is not like the valve grinding compounds on the market in auto industry. It is for machining in industry. I have had one can for 10 years.
reed

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 Post Posted: Thu Jun 14, 2012 12:09 am 
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Green or yellow depends on the type of material you have for valves & seats.
I would say yellow for Ti Valves and bronze seats. Soft...

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