It seems that those that do it are rather secretive about what they are actually doing. How much is actual machining on the engine, how much is “fitting” and shimming and then how much is part swapping?
As an example, what would be done to rework a NIB ST 60 for PA?

Matt

Ditto . Pull the backplate & inspect in strong light . " NEVER FUELED  " means it wont have rotted out .

The Ealier dual ring head is the open ' hemi ' . Later said to vary a bit between series, perhaps .

The tapped muffler bolt / blind hole ones are generally ( ALL ? ) P.D.P. , 4 or 3 ( concave head fins ) port ' windows ' .

If you MUST fiddle with it , theres info about , but appoach varies to a slight degree .

http://clamf.aerosports.net.au/newsletters/ACLN/Issue39.pdf

I believe Mr Garifoi may have known what he was doing , regarding FITS . So I wouldnt Alter Them !!!!!!!!!!!!!!

The Wrist Pin . ( or gudgeon pin , to those that speak english    ) is the archiles heel , on a USED MOTOR .
To the extent that if you DO dismantle any S Tigre ( or OS Max 40 old type ) you may be in for grief, a test of patiance at least .

the clean & ( singer Sewing Machine ) OIL , is only needed , after the fustration of extracting the thing . Wot Fun .

You can only drop the sleeve a iota , before you get sub piston induction . ( Open under piston at T D C ) only say 8 thou. ? on the 3 window P D P ones .
Most others open at ends from piston crank cut away , so adding to it wont help . Picture of alleded T & L below ( Tom Lay Stunt Tuned )



Most / All T & L have the Piston Baffle scalloped both sides , at the center . Said to alieviate  heat distortion of piston . Hight still full right thru tho .
A knife blade edge'll do it . the ' remove all burrs & sharp edges ' in the combustion chamber - piston , means . . .

Very Light dressing of baffle & baffle slot ' hard edges ' , in any full size engine this is to remove ' hot spots ' that can create ' Pre - Ignition ' .

Obviously theres the ' Cross Drilling ' the case for a central spray bar . If yours is the stock C L Intake , I wouldnt . Or do it & send the intake to ME . 
A Steel Rod , 4 m.m. / 5/32 through the Std spray bar hole , alows all sorts of measurements and parrallelity . a foot long . DONT drop it though .

a SEALED Front Bearing , if its a early one , may give better economy . plus theres bushed & unbushed rods .



theres the ' Big Jim ' with the reduced hight fins . 3/32 they say . ( 2.4 or 2.5 mm left ) . Tho some are ' No Fin ' . said to eliminate ' stumble ' .over cooling.

Best things to find a real nice muffler , Not a toungue if its the S P I prevelant one , due to back feeding / back pressure .
parently theres two I D outlets in Big Art ( adamisin ) mufflers . says Windy , on a tape . Small ones restrictive .

Std. ' Big Jim ' Intake is .312 inch . Also , a head a good fit , diameter matching bore , not loose. will help .

From picking the eyes outta the stuff we've seen . over the years . CLEANLYNESS is imperitive . Ferrari was No Smoking in the Engine assembly rooms .

One of the classis SPEED Engine Prep articals , http://www.avia-it.com/act/biblioteca/periodici/PDF%20Modelismo/Aeromodeller%20Annual/Aeromodeller%20annual%201968-69.pdf

If they got the clearances next to clapped out , they went best. As everyone new a engine went best just before it blew up . 
LOOSENING the fits was mainly to ease servicing . Correctly Aligned Interfearance Fits are what most things have most times . In high output engines .

Intro to mares nest , http://classicpattern.com/super-tigre-st-60/?lang=en Early liners 26 O.D. , soon revised to 26 . 5 m.m.

Is your engine the ' Muffler Lug ' on case , type . Gotta Picture . blue or red box . or big red box .

   For a Tiger .60  at least the ones with the muffler lugs.... when I set up a used one I replace the bearings with Japanese , European made or  American   not Chinese made. The Chinese don't fit... lightly hone the liner , new ring with .002" end gap , thin head shim .006" or less , I prefer the a true bore venturi with a spicket ,  .255" bore.  I can't see a reason to modify the engine.  I run high nitro .
  John L.

    Correction,   The True Bore diameter starts out at around   .225"
                           John L.

   Matt,
   Didn't you make an oversize Tiger a few years ago ?  Something like an .81  in a V60 case or was I dreaming ?
  John

Maybe another Matt but not me!

It seems that those that do it are rather secretive about what they are actually doing. How much is actual machining on the engine, how much is “fitting” and shimming and then how much is part swapping?
As an example, what would be done to rework a NIB ST 60 for PA?

Matt

Hi Matt
That will depend on what shape your new or used engine is in, I have Balanced blueprinted  setup over 1200 ST engines, and I have seen brand new ones with gaps at .010 and over, and some with ring gaps at near zero, both are NOT what you want, I have seen new ones with broken rings, especially the new pinned ones, Rods in backwards  etc.
There are many engines that are better custom fir and setup, Super Tigers have small counter weights and  benefit greatly from this,
You can improve by fitting the ring correctly
You can benefit from better bearings many times, you do not need expensive ceramic bearings, but ones with seals and phenolic gages are a much better deal
You can benefit from having some one who know, clean the engine and make sure all the tolerances  are in spec, For those who do not know what Blueprinting is, It is custom fitting and making sire all is in spec and  correct and clean
I DO NOT recommend ruining the case by drill holes thru it for a  restrictor venturi, You will be much better off with a true venturi and a  needle assembly in the stock location
You can improve the head on the ST engines, not by cutting the compression out, but by making sure deck clearance is right, and adding fins and machining a heat dam around the glow plug area,
For used engine, so many of them have mismatched parts, just in the  ST 60  Super Tiger had about 5 different cases, several different back plates, at least  5 different rods of different lengths, thicknesses, some total unbrushed  some bushed at the  bottom only some both, newer ones thinner front to back  etc
There was also many different heads, and thin sleeve   thick sleeve, chromes and  not  chromed, even though most have chromed molded into the case on the side,
There  were short rods, pistons with lower wrist pin holes  double rings, Dykes rings, standard single rings
There were also many different crankshafts, different counter weights, crank pin lengths, and  weights
Some of them have crankshafts that  are  loose on the rear bearing, NEW one and  used ones
There is a lot more to go into but  I think the point is made
The stock rings are very good  if it is round and has the correct gap, You will  NOT get more power or longer life with a  aftermarket ring, which can be just as bad or worse than stock
YOu can also get Needle assemblies that are much better than ST stock ones  or the  aftermarket ones

Regards
Randy

   Matt,
   Didn't you make an oversize Tiger a few years ago ?  Something like an .81  in a V60 case or was I dreaming ?
  John

WHO ~?

Maybe this OS80 , Seems good on that prop ,30-70fuel Enya 3 plugs.
But field isnt spitting distance , need to getserious withthe Aeroplane .



STANDARD T & L set up ,was baffle mod , will do a picture, as Ive two awaiting rings & bearings . plus the ' Bowman Ring 'when it was Frank .

24 stroke crank aka Stalker 76 , would make it a 76 , if things'd fitin .  as in a 24 x 24 S Tigre 60 . Think spi would get it the way .
The 24mm crankis the Stalker' Long stroke ' set up, with a Tall Case .  will see how close to 1 mm clearance at the big end we have, stock .

  Thanks Randy ,
  For straightening me out on this. You showed them to me in Muncie & offered to sell them to me I often  kick myself for letting the  .88 Tiger get away.
     John L.

   I believe Paul went to the electron side for power , too bad would enjoyed watching this beast fly a plane.

heres the pornograhs of mod er butch er ' altered ' pistons, as they came . Nothing to suggest these are the work of tom Lay ;
although He did similar , but radiused ; relief ' . The idea being we assume to relieve stress / bending though expansion of the exposed baffle.
Tho the glo plug & bypass may have a influance .
A inverted cone ( ish ) relief with radiused top . Along with radiusing or at least ' removeing sharp edge ' from the baffle
would seem to be reasonably safe , if done by steady hands. Unlike some pictures ( here ) we wont mention .

Depth sawed 1.6..1.7 mm angle at the apex of 60 degrees.
On the exhaust side, a chamfer was cut from the top of the cut to the bottom of the piston, see the sharp edge on the side of the purge.

This is a piston from a motor modified by Tom Lay. On such a motor, German Richard Kronmaer became the World Cup.
What does it give? I have no idea...

Liberated -> Pavlin 2000 Zaporizhia, Ukraine .

  My thoughts exactly, I can see someone holding the plane & the engine , prop , crutch assembly taking off alone.  I'm probably light years ahead by letting it go.

   No, this was just flipping it, it wasn't in a plane. But I can easily imagine that it would tear the nose off of one of Scott's airplanes if you tried to start it at full compression.

     Brett

It was really easy to start, the  15 or 16 inch props  helped a lot, ALL  of  Scott's engines  were high compression like that
I have used  several 74s  that had almost as much  pop to them, in  a Magnum and  several SVs, zero problem with the run  vibration  or  motor mounts  in those
Randy

I can tell you that is a good way to decrease the  power  and  increase  fuel usage , There were  also the  baffled  trimmed  to  lower the heights, which made a  ST 46  use  near  7 ounces of  fuel. 

   That was a trick from GMA, or at least that was the first time I had heard of it. His theory was that the engine ran too "strong" and that this would "tame it" and make it run "softer". Why in the world anyone would want to "tame" an ST46 was/is beyond me, but a lot of people did it.

    It seemed like it sort of worked for the ST G21/40. I recall losing some contest at Lunkin airport (in Intermediate, which tells you how long ago that was) to a kid with a P-40 of some sort with a "softened" G21/40, even though he was flying 75-80 degree maneuvers. It was 40 years ago, so clearly I am not bitter about it....

       Brett

[quote author=RandySmith
I have also made ones with taller baffles, they work much better

Randy


Hi Randy,

Is there some basic rule for determining the baffle height/distance from port? I want to make one engine with baffle piston. L

Hi Lauri
There is, but knowing your work I would  suggest a curved baffle, set it at about 20% of the piston diameter, from the intake ports,  go tall on the baffle, If you tell me  stroke  bore  i can give a good height estimate,  It would be  good to let me know what the  intake ports would look like , and  how much of the circle they would cover ,are you going to use a  Dykes Ring on this one ?

Randy

..could it be so that the v-notches in the ST baffle above are meant to act as poor man's Perry ports, to help cleaning up used gases from behind the baffle? L

Thank you Randy.

The bore/stroke are still same, 24/28mm.
I haven't cut any ports yet so I'm open to suggestions.
 With 6-port Schnuerle I have used following opening durations:
-Exhaust 22,8% (of stroke), that makes exh. port 6,40mm high.
-Intake 16,4%, 4,60mm high.
I think in crank degrees they are 130/110°.

The Schnuerle versions run really well but are a little too powerfull to my taste, at least with the older side resonance mufflers. Hopefully my new muffler will absorb some more power, but anyway I will reduce the intake port area in the next Schnuerle I do. I will add a drawing of the previous scavenging, maybe you get an idea of the port area.
But honestly, I have not started to draw the new scavenging, it's all in my head. But I think, because of the (Dykes-) ring, the intake has to be 3 separate windows and in 90° angle to the cylinder centerline.
By curved baffle, do you mean center of radius on exhaust side, like in some Stalkers?

Cheers, Lauri

OMG. Those are CLPA pornography!  Absolutely beautiful!

Ted Fancher


Oooops!  Lauri's pictures didn't come through on my reply which might make it sound a little...um...er...unusual.  Go back three posts and check out those liners he built and you'll se what I'm....um...er...talking about.

.....you mean these, Ted..? L

Yes Brett, I'm slowly getting the idea. Often if you did the complete opposite, it would be better.🤔

      There's an expression from the Old West - "shooting yourself in the foot".

     It's no small accomplishment to make a 46LA much less powerful than a Fox 35, but I have seen *a bunch* of them like that.

     Brett

   Paul Pomposo.

    Brett

Yep  great guy and  a  master craftsman  , and   handle maker  extraordinaire  !

Randy

WOW..
I'm totally amazed by the fact that someone took a ST60 and managed to turn it into a 88!

If I recall correctly, the ST60 case started life as a 51. So the ST60 was already rather "bored up" to begin with.
How did they do it?
Was it done by an increased stroke?
I would really like to know more about these ST60 mods.

Regards
Frank Wadle

Frank

It was a stroked home made crank
a bored ST with hand made piston,  sleeve, and  rings
Plus rod and  head
The ST  also makes for a  great 74, or  an easy 65

Randy