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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 1030070 times)

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Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #930 on: November 09, 2012, 09:49:35 PM »
Stan, the Arias pistons have very fine grooves all of the way around them.  They look like machining marks from when the parts were turned up on a lathe.  I looked carefully at the most worn parts of the pistons - the lower edges of the skirts perpendicular to the gudgeon pins.  The turning marks were still visible.  The piston skirt had not worn enough to smooth out the machining marks.

The pistons were set up loose according to Triumph Performance.  The 0.004 clearances we measured were not all that big.  This makes me suspect the coating wearing off might be the culprit, or these short and wide pistons are very, very, susceptible to rocking if the bore size is not spot on perfect.

The new monster pistons are Arias jobs with 2618 non-silicon alloy.  Arias recommends .003 clearances for street and .002 for race.  These are at .002.  They are not coated.  The WPC metal treatment is micro shot blasting.

I am clueless about this modern stuff.  Any insights are welcome.


Offline DND

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #931 on: November 09, 2012, 10:03:18 PM »
Are you sure those machine mark's were not put on the skirts for oil control, keeps the piston skirt from not getting skuffed and transferring alum onto the bore.

Don

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #932 on: November 10, 2012, 12:17:38 PM »
Don, I looked at all of my other pistons under the microscope.  The ones from the problem motor are down south.  You are right.  The grooves are not machining marks and it looks like they are deliberately put there as part of the surface finish.

Konkretekid sent me a link to some literature on piston alloys.  The low-silicon 2000 series alloys in these racing pistons are especially strong and well suited to turbo and fuel use.  In comparison to the 4000 series high silicon content alloy pistons, they do not wear as well and they are set up with a little more clearance.

The Arias piston to wall clearances are tightest for race motors, a little bit looser for the street, and they are looser for water cooled engines as opposed to air cooled motors.  This is the opposite of what we did in the old days.  This new stuff is definitely different.

Deck heights can be measured when the engine is put together.  I like to measure everything up before assembly and calculate the deck height by math.  It is easier.  The new and old engines use the same crank and crankcases. This makes the job much easier.  The standard OEM engine deck height was OK and it is my point of reference.

First, I bring everything I will measure to a room with temperature as close as I can get to 68 degrees.  This house is heated with wood and the rooms all have different temps.  The kitchen is closest to ideal.  All of the measuring tools are included.  Everything should be close to the same temp for measuring.  The items sit around for an hour so the tools and parts will be the same temp as the room.  That is why I am typing this post.  I am waiting.

Some parts are hard to measure because they are bigger than my micrometers.  The cylinders sit on a flat metal plate and a dial indicator is used to get a height reading.  I use my drill press table for the plate.  I measure the standard cylinders once, then the new ones, then the new ones again, then the standard ones.  The first and fourth readings should be the same and the second and third should be similar to each other.  This is ABBA measuring.     

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #933 on: November 11, 2012, 12:36:48 AM »
Does anyone know the compressed thickness of a standard original equipment Hinckley Triumph Bonneville cylinder base gasket?  A new or used one is OK.  This is the thickness of a part of the gasket that does not have a ring stamped on it.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #934 on: November 12, 2012, 01:01:28 PM »
The first task is to calculate the relationship between the old engine piston crown and the top of the old cylinder deck.  Is the crown below the deck, flush, or is it above?

Typical automotive practice is to simply measure the distance with the engine short block assembled and the pistons at top dead center.  Bikes, unlike cars have base gaskets with or without o-rings between cylinders and the crankcases and the cylinders often lift when the head is removed.  The piston crown to deck clearance measurement can be erroneous and the error makes the reading smaller than it should be.  This can lead to expensive errors in engine assembly.

The method I use is to measure down from the deck to the top of the upper piston ring wear mark.  It is 0.090 on this engine for both cylinders.  I take the measurement along the gudgeon pin axis.  The pistons rock in worn cylinders and the readings at 90 degrees to the pin axis can be misleading.  A lit magnifying glass helps to make this measurement more accurate.  It is hard to do with the naked eye.

Now I put something flat on the piston crown and I measure from the upper surface of the top ring to the flat surface.  This gives me the height of the crown above the ring.  It is 0.096 for both pistons. 

0.0096 - 0.090 = 0.006  The old pistons projected up 0.006 above the deck.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #935 on: November 12, 2012, 02:32:59 PM »
The next step is to measure the lengths of the Triumph rods from the old motor and the Carrillo rods for the new engine.  They were measured with a dial caliper and it is not the world's most accurate instrument.  I made four measurement on a rod and averaged them to get the "A" reading and did the same for the two B measurements and the final A one.  Then I compared the two and the Triumph and Carrillo rods are the same lengths within a thousandth of an inch.  The same crank will be used for both the old and the new motors.  This tells me the piston pins for the both engines will be the same distance out from the crankcase deck.

Now I measure the distance between the bottom of the gudgeon pins and the tops of the crowns of the old pistons.  One is 1.384 inches and the other is 1.387 inches.  The new pistons have a little 0.004 step in them and the new ones don't.  The bottom of pin to top of crown measurements for the new are:  1.383 + .004 = 1.387  and 1.385 + 0.004 = 1.389.  The rods are the same length and the new pistons are up to .002 inches taller.  This tells me the new pistons will project from the bore up to 0.002 inches more than the old ones.



       

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #936 on: November 12, 2012, 04:20:40 PM »
The picture shows the part of the cylinder head I am worried about.  I do not want the piston to hit it.  It is flat and flush with the outer surface that has the stud holes.  Now I measure the old head gasket thickness.  It is 0.028.  Estimating piston travel using a wear mark is plus or minus 0.01 inches, as a guess.  The piston to head clearance for the old motor is calculated like this.  Head gasket thickness - projection of piston crown above deck + or - the error, or 0.028 - 0.006 + 0.010 = 0.032 maximum, or 0.028 - 0.006 - 0.010 = 0.012 minimum.  Sorta tight.  0.030 is a typical recommended clearance.  This engine had ten LSR runs on it and it was revved up pretty high for a couple of them.  There is no sign of piston to head contact.

In past years I have handled the old base gaskets a lot and I am pretty sure they are not thicker than the head gaskets.  Using this assumption, the combined thickness of the old cylinder stack is 0.028 (head gasket) + 2.830 (cylinders) + 0.28 = 2.886 inches.  Now I remember the new pistons project 0.002 more past the deck than the old.  The combined thickness of the new cylinder stack should be at least 2.886 + 0.002 = 2.888 inches at a minimum.

The new cylinder stack is 0.042 (new head gasket) + 2.829 (new cylinders) + 0.016 (new base gasket) = 2.887 inches.  Close enough.  This is a Triumph and not the space shuttle.  That was the last thing to check.  Now it is putting it together time.

Offline Freud

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #937 on: November 12, 2012, 05:45:52 PM »
Quote:

The new pistons have a little 0.004 step in them and the new ones don't.

Which new ones?

FREUD
Since '63

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #938 on: November 14, 2012, 12:10:04 AM »
The new ones have the step and the old ones do not.  I was looking at all that work I did and figure that the old method of putting everything together, turning the engine over while squashing a piece of oily used chewing gum on top of the piston, and measuring its thickness might have been easier and a lot less mental. 

Offline Old Scrambler

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #939 on: November 15, 2012, 09:48:05 AM »
a-HA! The old reliable USED plastigage trick........I prefer the wintegreen flavor :lol:
2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2018 AMA Record - 750cc M-CG HONDA CB750 sohc - 136.6 mph
2018 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 143.005 mph
2018 AMA Record - 750cc M-CF HONDA CB750 sohc - 139.85 mph
2018 AMA Record - 750cc MPS-CF HONDA CB750 sohc - 144.2025 mph

Chassis Builder / Tuner: Dave Murre

Offline manta22

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #940 on: November 15, 2012, 09:57:34 AM »
... but does the Plastigage loose its flavor on the bedpost over night?   :-D

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Peter Jack

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #941 on: November 15, 2012, 10:00:42 AM »
When others used to criticize Plastigauge a friend of mine used to say "It knows, it's in there!"  :roll: :roll: :-D

Pete

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #942 on: November 16, 2012, 12:17:49 AM »
There is not much of a champfer on he bottom of these barrels, the pistons are wide, and the rings were made to order.  I had to be really careful when I put the barrels on.  None of the ring compressors I had would work.  Finally, after a couple of hours of fiddling and trying different things, the barrels softly slid down over the pistons.  Ah, what a sweet feeling.  Total relief and satisfaction from a hard job completed.  Then I noticed something.  One piston is backwards.

Offline generatorshovel

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    • http://www.dlra.org.au/forum/viewtopic.php?t=556
Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #943 on: November 16, 2012, 01:43:26 AM »
  Then I noticed something.  One piston is backwards.
                                                                 

Dontcha HATE when that happens ?, it's a bit like trying to spin a supercharger backwards  :roll:
Tiny
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I would prefer to make horsepower, rather than buy, or hya it, regardless of the difficulties involved , as it would then be MINE

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #944 on: November 17, 2012, 01:41:54 AM »
Tiny, putting a piston in donkey backwards.  Something I would never do.  Its the mice.  They are not strong individually.  They are numerous and they see good in the dark.  The little rascals came in at night and turned it around.  They just want to make sure I am paying attention.  That's the only logical explanation.  I am sure of this.