Big Bore question

[dukekleman]

The upper portion of the cylinder bore is exposed to the most heat due to flame front and PPR after ignition. The cast iron cylinder doesn't dissipate heat as well as the aluminum cylinder head as we know. Giving the heat a pathway to dissipate from the cast iron into the aluminum via the gasket and RA surface area is looked at as an advantage/advancement.
Thermo imaging cameras show a very interesting picture of heat distribution through colored imagery and numbers

[T. Cotten]

So these modern gaskets, Duke,..

If they transfer heat better, wouldn't that take it to the cylinders?

....Cotten
PS: My 1993-vintage Sunnen honing oil has aged nicely!

[dukekleman]

MLS (Multi-layer steel) is a layered riveted gasket with integrated embossments and coated in a mil layer of Viton. In order for them to work as engineered (Seal and Transfer Heat) correctly for prolonged mileage, they require a different surface finish. The Japanese manufactures have used them in the motorcycle world far before the American manufactures. What I noted is that as aftermarket companies started using them for Harley Davidsons, they were torqueing them wrong. The Japanese have a different torque procedure than say Cometic...
The first company introducing them that I recall was Branded "Motor factory" from a company called Chrome Specialties. Now you see them branded/produced by others...Also the American bike manufactures (Harley Davidson, Indian and Victory) have used them in OEM production for years now. These are not to be confused with SLS and AFM...
On HD series engines that I bore and hone often, I've built into my torque plate an adjustable lower plate for the spigot area. "Panting" or "Belling" as some call it is a major problem just as Cotton pointed out. There is an art to honing cylinders correctly and a science to the honing oil formulation used taught to me by my friends Doug Coffee and Joe Mondello. I must give credit where credit's due...
I measure a lot of new cylinders for Harley Davidson's! Most do not come close to passing standards set.
The spigot area is often a issue and starts by having patience during the boring process. To much tooling pressure starts to mess it up prior to honing which only gets worse from stone pressure. Hone stroke, Over stroke, Dwell and Stone Pressure experience is key to proper X & Y axis's measurements in the end.
I like to use a infrared temperature gun to monitor the heat created by the friction of honing. The heat definitely effects cylinder measurements!
Last note on cylinder spigots, When it comes to Big Bore/and or stroker motors, one must be careful to bore the crankcases correctly for the oversized spigots I've seen them to tight and cause piston skirt issues due to expansion restrictions under growth. Also the crank case fasteners can contact the spigot and cause distortion.
Fastener Stress: Cylinder structural integrity is huge and I've seen fasteners cause distortion to cylinder bores just as you pointed out in the image above. This should not be overlooked and adds to the importance of torque plating with gaskets being used in the final build.

[T. Cotten]

I really don't know the mil-profile my stones produce, Duke!

But its sharp and bright enough to grab a composite gasket; What is "MLS"?

Once again, I preferred to grind because it was much faster, easier for me, and removed minimal stock, thus keeping compression pretty much the same. I stopped spot-facing when I realized it just gave the inserts somewhere to go.

If I can return to stressing for fitting to the pistons,
Here is an inverted Chief cylinder (which distort far, far less than an HD) where you can see the dark patch where the stone hasn't touched where the bore wall is pulled outward, by the fastener-stress of the base stud right next to it:
distort.jpg

At .070" and over over-bores, I have observed HD spigots distort both inward and outward a full thou and a half. If not stressed as if installed while honed, the spigots will rub the piston skirts at a normal clearance.

....Cotten

[dukekleman]

Spot face machining head bolt inserts. One a Panhead the other a Shovelhead. See images...
Panhead Cylinder head.pngShovelhead Cylinder head.png
The RA finished I use on these is for a conventional head gasket. The photo below shows the RA for a MLS head gasket...
Twin Cam cylinder head MLS RA.jpgTwin Cam cylinder head.pngCylinder head surfacing.png

[T. Cotten]

While we continue to ignore where the fuse gets lit most often, Folks,...

A few observations on head gasket surfaces:
The headbolt inserts I remember on Shovels were recessed, however the heads were still not 'flat'. I have no pics from the era, but a light grind on a flat surface often displayed low spots over both intake and exhaust ports. Metal moves.
(I preferred to grind them flat, rather than machine, as it took the least time (expense), and removed the least material.)

Pans certainly suffer from 'pulled' inserts, and I feel decades of duty were enough, although over-torquing made things worse:
SRTGRND2.jpg

Even this Chief cylinder deck shows a depression over both exhaust and intake ports:

warpage.jpg

deckwarp.jpg
The exhaust was detectable with the feeler gauge, but only a light grind illustrated the intake warpage.

Inspection must be diligent; Any stone unturned hides something that will bite you.

....Cotten

[exeric]

Thanks to Tom, and Duke for their patience, and indulging my remedial motor questing. Also my apologies to OWG for leading things off topic.

[dukekleman]

I agree, I've bored a number of Panheads over the years at .080". All of them I'll call local bikes because I run across them time to time. Out of all of them I've done, the last one is has been over 25 years ago, they all still run fine without issue. I could ramble on about what has built my confidence in using .080" pistons, because at first I was skeptical. I'll just share that I've been with a couple of these Panheads bored .080" on trips that have covered multiple states, various climates and elevation change, they survived just fine.
RA finish is very important and should not be overlooked. RVK and RPK are considered when machining any surface for particular applications. There are multiple numbers used in each application if you will. Wheel hubs, brake drums, connecting rods, pinion/sprocket shaft races, valve guides, gasket surfaces, cylinder walls and exactly what Cotton said, sleeving. I've seen sleeve jobs that act as an insulator of heat transfer like the images shown above. A very fine RA finish along with X and Y measurements within 0.0002" is required between your interference surfaces when sleeving. I prefer to resurface the base gasket and head gasket areas to not only get the correct finish for the gasket of the era being used but also to insure things are square if you will... I've seen a few shops around my area skip this important step.

[T. Cotten]

Thanks Cotten;
All comes down to resources and finding a good craftsman you can trust.

As I posted, Paul,

Any competent auto machinist should be capable, if you arm him with some specialized tooling, and most important, information. Finding an experienced hand who doesn't think he knows better can be a problem.

Most auto shops who install sleeves deal only with water-cooled motors, where heat transfer isn't life-or-death.
For an air-cooled motor, the thou and a half interference for a sleeve doesn't encourage heat transfer, so the finish to accept the sleeve must be as micro-fine as possible; Even a plateau finish only conducts at the plateaus. ("Seal-Lock" fills the rest of the voids.)
Graciously, the LA sleeves I used were almost reflective (but that was more than a few years back.)

Boring for a sleeve blows out the casting much farther than the largest overbore, so I prefer the overbore.

...Cotten
PS: Here's what over-zealous sleeving
can do:

Perfdcyl Indian.jpg

perfdcyl 3.jpg
Dixie had Pan/Shovel pistons up to a hundred over. I fit a set, but I bet the fellow still has them on the shelf: He's a collector.

[PaulCDF]

Thanks Cotten;
All comes down to resources and finding a good craftsman you can trust.

[T. Cotten]

Not to hijack OWGs thread (He said as he hijacked the thread).
Eric brings up a point "a nice set of correct year cylinders without going to sleeves"
Is there something inherently weak with sleeved cylinders? Or is it the craftsmanship or lack there of that goes into the sleeving?
Not looking to be contentious, just trying to learn. As original parts for antique bikes become ever scarcer.
Is it a "judging thing" not to use good reproduction cylinders?

Repop cylinders can be quite a problem, Paul!

Not that there may be quality now available, but its a still a choice between originality (plus getting your money's worth out of what you got...), and compromises cast into the repops. (I have an oriental pan cylinder that had been bored to paper-thin at thirty over, and ran fine until it tossed a wristpin clip. Then I put my fingernail through it:

PERFDCYL.jpg

Sleeving can be performed correctly of course, but I seriously consider a larger overbore much safer and cheaper, if performed correctly. Sleeving involves more procedures, and as this Chief sleeve shows, a careless installation spells disaster: Sleeves insulate even when perfect, but a toolmark can guarantee a melt-down..

SLEVBURN.jpg
(Outside of removed Chief sleeve.)

We can get into techniques, but everything depends upon what you have to work with.


....Cotten
PS: Late edit, Folks,
I found a pic of the cylinder bore for the burnt sleeve; You can see the horrendous tool-chatter contributing to the melt-down.

CHATTER.jpg

[exeric]

I've had an Indian, and a Harley with sleeved cylinders and no problems. I do wonder if how a motorcycle is used can cause problems assuming the motor was well built. In other words, if a bike is ridden long distances and continuous hours, or just used around town, and short pleasure rides. I'll bet there is a lot of good data from Cannonball engine builders but that seem to be closely guarded stuff. Here at the AMCA forum we rely on freely given info from Cotten, Dukekleman, Robbie, and others with real world experience; which I thank them for.

[PaulCDF]

Not to hijack OWGs thread (He said as he hijacked the thread).
Eric brings up a point "a nice set of correct year cylinders without going to sleeves"
Is there something inherently weak with sleeved cylinders? Or is it the craftsmanship or lack there of that goes into the sleeving?
Not looking to be contentious, just trying to learn. As original parts for antique bikes become ever scarcer.
Is it a "judging thing" not to use good reproduction cylinders?

[T. Cotten]

One can only make an assumption in this case and my assumption/experience has seen improper torque and re-torque on the rear cylinder, left side rear head bolt to be one of the most common. The clutch cable minor adjuster gets in the way. People use dog bone adaptors that contact the cable adjuster falsifying torque value. I've seen many technicians do this when mentoring them.
Assuming points are being used in this situation, a technician must be aware of the advance weight pedestal fitment. Depending on the camshaft manufacturer and the advance assembly manufacturer, I've seen the point gap vary dramatically front the front cylinder lobe to the rear cylinder lobe. Sometimes a light tap on the shaft can true things up nicely for equal gap settings. This causes obvious timing issues...

The whole torque technique, Duke,

Will always demand prep, proper wrenches, and observation, etc. But there's been far too many burnt gaskets that weren't by the clutch adjustor (even if the model had one).

They always run for a while, sometimes a long time. Then temps spike, for some reason.

Points gap issues are not just a Shovel concern of course, and certainly affect performance. But causing one head to burn and not the other would take a pretty wonky assembly!

Burnt gaskets have always plagued internal combustion engines, and the most common cause has always been there too.

....Cotten
PS: Anybody remember when the early '80s models started dropping valve seats? That took a lot of heat, yet the gaskets survived.

[dukekleman]

One can only make an assumption in this case and my assumption/experience has seen improper torque and re-torque on the rear cylinder, left side rear head bolt to be one of the most common. The clutch cable minor adjuster gets in the way. People use dog bone adaptors that contact the cable adjuster falsifying torque value. I've seen many technicians do this when mentoring them.
Assuming points are being used in this situation, a technician must be aware of the advance weight pedestal fitment. Depending on the camshaft manufacturer and the advance assembly manufacturer, I've seen the point gap vary dramatically front the front cylinder lobe to the rear cylinder lobe. Sometimes a light tap on the shaft can true things up nicely for equal gap settings. This causes obvious timing issues...