Valve seat cutter: total waste of money?

[JW113]

My understanding of valve spring motion:

You cannot see attachments on this board.

If the springs twist as they are compressed, rotate the valve, and "something" grabs the valve and keeps it from rotating back in the opposite direction, why do they put valve rotators at the bottom of the spring in some/many engine designs? Obviously, not Harley-Davidson.

-JW

[Don D]

No comment on rotators, not used on a HD.
Consider that the valve locks are collets. Sometimes they fit tightly in the recess of the retainer and lock the stem to the retainer, and sometimes not.
https://youtu.be/6Vz4mjPKXJ0

[kd]

   I was looking for some of the spintron and laser camera video stuff.  There was one in na HTT thread about a year ago in a discussion over beehive, conical, double wound and springs with dampeners. The link you posted is as good as any of them if not even more exaggerated than most.  Some show the unbelievable harmonic vibration in the spring more and it becomes easy to see how the keepers could at points in the stroke of the valve lose traction and allow the spring coil rotation to drive the valve and release it.  You can't compress a coil spring without the ends moving.  There are plenty of IC engine engineering papers to be found that comment on the extended valve and seat life imparted to the rotating valve phenomena. Almost all of them state the benefits (up to 40% and more extended valve and seat life) is lost as the mean RPM is lowered and the valve begins to stall.

[Don D]

Off topic but positive rotators are beneficial for gas (or LP) engines running near full load for extended periods of operation. Other methods to cool the exhaust valves used was sodium filling. Gensets, some marine and industrial applications. There were a few big block Chevys that used them in trucks. The aftermarket even make eliminators for those LOL.

[JW113]

OK that's pretty interesting, and I still don't quite understand the mechanism that causes that to happen. In the text, it did say "at extreme RPM". Sure would like to see a video of the same thing but at 3000 RPM. As evident by my valve spring tips, that sure isn't happening in my case. Guess I need to take it up to 10,000 RPMs more often!

kd, I totally understand that a compressed coil spring twists. It's the same mechanical action as taking a long straight spring metal rod and twisting it radially, ala a torsion bar. But in both cases, when the force on the spring/bar is released, the spring twists the opposite direction back to the original position. That's the part I'm hung up on. Something has to "hold" the valve if the spring twists it in direction A, while the spring relaxes back in direction B. Ala valve rotators. If no rotators, what is providing the one way clutch effect?

I don't get it. And the other part I don't get, if valves do this naturally, why do automotive engineers add valve rotators?

-JW

[JW113]

OK, after giving this another think, I think I understand (at least in that Spintron video) why those valve springs were rotating and in only one direction.

As we all know, as RPMs go up, valve control goes down on the downhill side of the cam lobe. At some point, the spring can't push the valve train back down as fast as what the cam is dropping the tappet, hence "valve float". So think about that. On the uphill side of the cam lobe, the spring (and valve) get compressed, and the coil spring twists a little bit, rotating the valve. But if we're up near or past valve float, that spring is now also "floating" between the collars, not applying much, if any, pressure on the valve, and is free to twist back to it's home state without rotating the valve with it.

So yes, at those screamin' high RPMs, I can totally see how those springs and valves spin like whirling dervishes. But at "normal" RPMs, like most street bikes live in, I don't see it. And my data point of one says they don't.

That's my story and I'm sticking to it!
 

(unless you have a better explanation!)

For you guys that build heads, got any shop pics of what the valve tips look like on heads before you rebuild them? Would be interesting to see.

-JW

[Don D]

They either look like yours or are uniformly polished. Simple as that. Some rotate and others don't. A loose fitting lock in the retainer is not a good thing and can result in failures. The lock is meant to be a collet as I stated before. This is so easy to test during assembly and I reject them if they do not lock properly. I also do not use aluminum retainers. TI, Tool Steel, or Steel.

There are many qualified shops that can fix these heads, this is not a do it yourself proposition with hand tools or gizmos from ebay. Or your mention of new heads is also a possibility and the bike is back on the road. It will be much better than new either way. All the theory in the world does not solve this, it just takes parts and machine work. If you want to learn more about valve train dynamics carry on, I suggest speed-talk.com

[JW113]

Yes, I agree, I could throw money (and time) at these stock heads, and the result would probably be just fine for what I intend to do with it. But at the end of the day, they will still be AMF era heads, with less than high quality materials and workmanship. If this bike was a 99 point AMCA show bike, indeed that would be the way to go. At the same time, I could take the same money, and with just a wee bit more, have some nice high quality S&S heads, better materials, better ports, and perfectly flat gasket surfaces that (hopefully) won't weep. And this is exactly what I am doing, they will be here in a week.

Regarding valve rotation or not, I'm not trying to solve anything, just trying to make sense of it. In fact, in my case, I'm not worried about it one iota.

cheers,
-JW

[Don D]

The shovel like you said is a low rpm torque producer. Never the greatest of valve oil sealing or ring seal and fat mixtures all reminiscent of even much more coveted foreign exotic cars of the era. The valves don't need to turn. In fact turning the valve on the exhaust may even hasten recession with those old cast seats In a higher rpm clean burning similar era Mercedes engine they used rotators because they burned exhaust valves without them. The rotators help with the release of heat and not allowing local hot spots. Never seen a burned valve on a shovel but I have not seen many thousands either like the later models.

[capn]

I just put new heads and KB 8.3 pistons in my 76 and the way it runs is like night and day difference.

[turboprop]

Yes, I agree, I could throw money (and time) at these stock heads, and the result would probably be just fine for what I intend to do with it. But at the end of the day, they will still be AMF era heads, with less than high quality materials and workmanship. If this bike was a 99 point AMCA show bike, indeed that would be the way to go. At the same time, I could take the same money, and with just a wee bit more, have some nice high quality S&S heads, better materials, better ports, and perfectly flat gasket surfaces that (hopefully) won't weep. And this is exactly what I am doing, they will be here in a week.

Regarding valve rotation or not, I'm not trying to solve anything, just trying to make sense of it. In fact, in my case, I'm not worried about it one iota.

cheers,
-JW

Those trouble heads from S&S are a no brainer. I have used a few sets of them. Perfect right out of the box. Enjoy.

[JW113]

Yes, am really looking forward to getting all the parts back, and put this ancient beast back together. What started out as a flywheel rebuild/balance by Dark Horse has turned into new S&S heads, and now S&S cases as well. Like Capn, will be using KB 8.5:1 forged pistons, and an Andrews #2 cam with Jims Powerglide tappets. I think this is going to be a completely different animal than what I took apart!

-JW

[76shuvlinoff]

You're a better man than I JW. I pulled my leaking vibrating numbers matching factory mill of questionable care and handling in 2004 then installed a full S&S "shovel" repop and never looked back. However I think I have changed the cam in it 4-5 times now and there's been 3 different carbs on it. The 76 mill still sits on the same milk crate where I put it. Once in a while I put oil in the spark plug holes and roll it over. It's a problem for the next guy now.

 Good luck with your overhaul. I am sure you'll come out the other end in love all over again. 

 

[JW113]

Well Mark, we'll see who's the better man. I mean, after all is said and done, about the only thing left of it that is "stock" will be the flywheels (not the shafts), the rods, and the cylinders. About every thing else is aftermarket, and non-matching frame/engine. I'm sure that 93" would run circles around my dinky 74", and for the money I'm throwing at it, maybe should have just bought a whole engine! But I figure a 74" is easier to tame the vibes than a stroker/big bore, and smooth running is more important to me than big power. At least for this old FLH. I think you're right, probably going to really dig this mill once it's all back together and broken in.

-JW

[Ohio HD]

You still have time for 3-5/8" bore on standard stroke, 82"........

Just give the piston weights to Darkhorse and have the cases bored.     

[JW113]

74 cubes is plenty for an old geez like me.

Then again...

 

-JW

[Ohio HD]

I took a look at the catalog, they're only showing 3-5/8" bore for 4-1/4" stroke and longer. They used to make them for 3-31/32" bore. You probably would just need to call them.

[76shuvlinoff]

74 cubes is plenty for an old geez like me.

Then again...

 

-JW

Then again..... It's a sickness. 

[72fl]

You're a better man than I JW. I pulled my leaking vibrating numbers matching factory mill of questionable care and handling in 2004 then installed a full S&S "shovel" repop and never looked back. However I think I have changed the cam in it 4-5 times now and there's been 3 different carbs on it. The 76 mill still sits on the same milk crate where I put it. Once in a while I put oil in the spark plug holes and roll it over. It's a problem for the next guy now.

 Good luck with your overhaul. I am sure you'll come out the other end in love all over again. 

 

Heck Mark put me in line for that Milk Crate      

[capn]

Mine is 80 inch but have owned 3 74 inch and I agree with JW about the 74 seeming smoother.

[JW113]

Then again..... It's a sickness. 

Not to worry about that, Mark. I've been vaccinated.
 

My understanding (jump on me and kick an education into me if this is wrong) is that the 74's feel smoother than the 80's because they use that thick heavy left side flywheel. More flywheel mass makes kick starting more effective. The Electra Glide didn't really need a kick starter, since they were all electric start, even though many (mine included) either came with, or had one, added. Many of FX models, especially the early ones, were kick only. But after 1978-1/2, when they rolled out the 80" motor, I don't believe any of the big twins came kick only.

Vibration is all about rotating mass and reciprocating mass. The more rotating mass (assuming it's "balanced"), and less reciprocating mass, yields less vibration. So yes, heavy flywheels can help mitigate the HD's inherent out of balance 45 degree design.

I'm all in for a 74" motor for this bike. The only reason to go bigger is for more power, which in my case, the bike does not need. It's an old man cruiser, not a drag bike.

cheers,
JW

[Ohio HD]

I ride my 124" TC like a little old lady headed to bingo!     

[Hossamania]

Ridden to church on Sundays...

[JSD]

I just purchased S&S shovel Heads and was disappointed with port finish from there casting so had to Disassemble and have them cleaned up. One valve seal was not fitted correct and also they have steel guides. As far as valve rotation on my TC with Roller rockers .619 lift Crane Cams, 180 seat pressure i have lifted rocker covers to fit Vulcan billet supports after 2000 k i noticed the roller to valve contact witness marks to be dead centered ( A bit of Luck for me ) so it told me the valves have not been rotating 
   

[JW113]

I too was a little surprised by the rough sand cast appearance of the ports in the S&S heads I bought for mine. However, it's been established through flow bench testing that polished ports actually flow less than ports with a textured finish. Why? Air sticks to the smooth metal finish and creates drag, whereas the air that is in all the "cracks" in the textured finish act like bearings for the air moving past it.

At least that's what I read on the interweb somewhere.

 

Mine's not a competition bike, so I don't really have much concern about it.

-JW