Done really good valve jobs, .001 with the runout gauge on the 45 .Done shlock lapping crap,lasts less time running than fixing it.What is your take? Shutting my mouth,on this one.All responses welcome,good or bad.....
Valve job quality.....
- Thread starter Abodybomber
- Start date
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skrews
Well-Known Member
Blows me away how many lazy *** "machinists" don't lap the seats as they go. Should be a part of every valve job.
C130 Chief
Mechanical Genius
Lapping is no replacement for a proper valve job, but does have it's place. Lapping is OK to clean up basically good concentric valves and seats. But, lapping will widen the seat contact area. Lapping also does nothing to address excessive guide clearance.
If I have a set of heads off for maintenance, I lightly lap the valves. I do this mostly to check the valves for warpage and concentricity. I look for an even grey band on both the valve and seat with a minimum of lapping. Usually 10 back-forth turns with fine paste. This is enough to show any defects without removing much metal.
If I have a set of heads off for maintenance, I lightly lap the valves. I do this mostly to check the valves for warpage and concentricity. I look for an even grey band on both the valve and seat with a minimum of lapping. Usually 10 back-forth turns with fine paste. This is enough to show any defects without removing much metal.
moper
Well-Known Member
That valve job's crap. Runout should be less than .0001 on anything considered performance or modern. Laping compound is no part of a good valve job. It's meant like C130 uses it for - to blend imperfections on moderately worn or stone ground seats so they seal better. When the valves and seats are done right on modern equipment, you don't need to lap them. Everything mates up perfectly.
RAMM
Well-Known Member
You can get runout on a valve job to less than a tenth of a thou?!!! Are you personally able to achieve that? Or are you just stating that's what it should be or you would find it unacceptable? Just looking for some clarification at this point. J.Rob
You don't need "modern equipment" for a good valve job. Just someone who knows what they are doing, and will take the time to do it right. I use lapping as a quality check to visually check angles and widths. I usually check 1 intake and 1 exhaust per head. You will never remove enough material lapping to get a good seal, let alone narrow your head seats or valve faces to specifications.
Brian Hafliger
Well-Known Member
So if you have .002 of guide clearance, why do you need .001 of seat runout? Anyone???
skrews
Well-Known Member
x2
I use 3D cutters on a Serdi, and I can say that even the best seat job should be verified by marking all the seats with dykem and lightly lapping. This also smooths out the face of the seat. I don't care how clean a cut or grind you think you put on the seat, when viewed under magnification it will look like crap. Once lapped they look great.
moper
Well-Known Member
No, that's beyond my and my equipment's ability (Petersen TCM-25/Souix valve grinder in my garage). I used to be able to hold runout to a thou or less with it but I haven't done any head work personally since before my divorce (years) and I was never doing it as "production" work.
That being said the quality I get is that high at the shop I use. My runout gage indicates in thousanths but theirs is half that and the couple times I've watched the needle didn't move.
Brian - tell me why...
C130 Chief
Mechanical Genius
Valves rotate, round valves close and seal more consistently in round seats? Also, that .002 guide clearance is cold, on the bench. A hot valve probably reduces that.
RAMM
Well-Known Member
Ok so you have the equipment AND the knowledge to do your own headwork and you still use a shop for any work you need done?!? Ok I can sort of understand that.
Just what kind of equipment does this shop use? I truly am curious because I have used MANY different headshops/stone setups/methods and NONE of them can produce runout less than .001" without serious intense effort and scrutiny.
I agree with just about every post in this thread and would like to add that for a few years I have been widening my valve seats beyond what some would consider the "norm" for Hi-perf use and although the flow bench numbers aren't as good as a "thin" seat --I have picked up substantial power. Also upon teardown for refresh or inspection the seats look and seal great.
I like crisp defined angles and wide seats. I lightly lap using a fine compund just for a visual confirmation and to make me feel good. J.Rob
p.s. Let's not even get into what happens to the valvejob when the head is torqued. No I don't use a torque plate bolted to the head although I imagine a tenth or two might show up there.
Brian Hafliger
Well-Known Member
The guide hole grows too, otherwise .0015 that so many guys like to use would go to nothing flat!
100% seal is just that...100%! There is no more seal.
If you have .002 of valve guide clearance and .001 of seat runout you still have more runout since it's based on guide clearance.
moper
Well-Known Member
I'll shorten defending my choice it to at the time, the healthiest (but honestly hardest and most painful) choice for me was to stop doing everything car related. Suffice to say this level of quality can be done with attention to detail, talent, and good equipment. I haven't been there in over a year because my last customer was body and paint, and then I renovated 1/2 of my house - but IIRC they use a Serdi 3.0 and VVR120.
I have a thought on this but I'm curious what your and Brian's takes are on this - what are your thoughts on why the wider seat makes more power when the bench might indicate the opposite?
I also agree with Brian - While this particular conversation is centered on seats because that's what I commented on first - the combination of machinist, seat accuracy, guide clearance, length of guide, and quality of the valve cutting all make up the potential quality of the valve job.
Babyblue66
Cool dude
I've used a Serdi a few times. Vacuum check them and I've never had to lap them.
Brian Hafliger
Well-Known Member
The only way to know this is to do a narrow seat, dyno, then remove the heads, widen the seat, and dyno again. Have you done this? If so, kudos to you because I know of nobody that's done this...however Meaux has said many times that narrower valve jobs either make more HP AND use less fuel, or make the same HP and use less fuel.
I used to do fairly wide seats until I noticed narrower seats flowed better and those engines seemed to run better, all parts equal from build to build. That's why I leave my ports rough too, because the use less fuel and make more power but they look unimpressive compared to sand rolled finish.
I guess I just do what works for me, and makes our engines perform the best for our customers. I know there is more than one way to build an engine and my way may not be like everybody else's and for me this is what makes engine building so fun and challenging!
Brian
moper
Well-Known Member
lol... no - that's not within the realm of my financial ability and I'm well aware of Larry's thoughts. I have tremendous respetc for his (and others') abilities. We've talked before as I own Pipemax. And along the lines of smoothness - I also get ribbed for the surface features I leave in my ports. The last head I had flowed his comments included "it really surprised me after looking at it"...lol
Where I was going was, at least in my opinion, the wider seat gives a seat and valve with more "inaccuracy" (that being runout on the valve, eccentricity of the seat angle, guide clearace, etc) a better shot at sealing earlier in the compression stroke. A narrow seat angle will always make more power, so long as the parts come together smoothly and controlled. Basically - narrower seats reduce the effectiveness of inaccurate work. Wider seats will work regardless of accuracy. At least, that's my feeling anyway.
And to clarify - I respect your abilities and drive, and Robs, and others' here. I like deep technical discussion.
Where I was going was, at least in my opinion, the wider seat gives a seat and valve with more "inaccuracy" (that being runout on the valve, eccentricity of the seat angle, guide clearace, etc) a better shot at sealing earlier in the compression stroke. A narrow seat angle will always make more power, so long as the parts come together smoothly and controlled. Basically - narrower seats reduce the effectiveness of inaccurate work. Wider seats will work regardless of accuracy. At least, that's my feeling anyway.
And to clarify - I respect your abilities and drive, and Robs, and others' here. I like deep technical discussion.
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