Will the gut's from a30 S Max engine interchange with a 35 O S Stunt ?  I want to mount a muffler on the 30, but it doesn't have mounting holes in the block for a muffler, so any help or suggestions  will help..   thanks a lot

'Legger,

My understanding is that you can convert displacements between the OS Max-S.30 and the S.35.  I was told that the difference is the liner, piston and head. I looked up the factory instruction sheets and compared them, which shows the head gasket and piston pins are also different.

I have a pair of well-worn .30's and now a fairly good .35S. But I have not tried swapping parts--yet.

Regarding the muffler, I bought a pair of tongue mufflers for the 30s from Jim Lee. I had to modify the crankcases on both engines to provide a clearance hole, front and back, for these to mount properly. Put the case in a drill press to get the thru holes, then touched the bypass side with a Dremel to make a seat for the screw head. If I had a mill I would have spotfaced these instead.

I need to pull apart the .35S so I can put holes in the case on it. Still on the To Do list....

Good luck,

Dave


Part number comparison for OS Max-S .30
Piston and liner assembly     2S03
Cylinder Head                      2S04
Piston Pin                            2906
Head Gasket                        214A
Connecting Rod                    2305
Crankshaft                           3S02

OS Max-S .35
Piston and Liner Assy          3S03
Cylinder Head                     3S04
Piston Pin                            3506
Head Gasket                        3514A
Connecting Rod                    2305
Crankshaft                           3S02

And except the head gasket.

Randy,

I have a couple of OS Max S .35s.   I have seen OS Max S .35s on ebay with a strap on OS 703 muffler.  Do you have the 703 or is that an ebay item? I don't know what an OS Jestream muffler is, but is that also an ebay item?
  Could you tell me what the number is for the muffler that you said goes with an OS .25 (FP? LA?) and is that a muffler that is still stocked by you or other suppliers?  One of my OS Max S .35s is on a Cosmic Wind that needs nose weight.  The other is soon to go on a Francherized Twister given me by Doc Holliday and I suspect it will need nose weight as well.  Both of my engines have the holes inside the edge of the exhaust tapped.


Thanks,

Joe Ed Pederson
Cuba, Missouri

Hi Joe

I have tongue  mufflers  that will fit a  drill  OS 30 or  35  in stock for sale , and  ALL  the stock  FP or  LA 25s mufflers  will fit the  drilled  OS 30 or 35s,  The  Jet Stream muffler is 3 main pieces, and is the same  clam shell  type that  the  MERCO muffler is,  The  703  is  a  OS  strap on muffler,  YOu can find the  703s on Ebay or elsewhere, the Jet Stream is  a lot harder  to find
Do you have one that has been drilled? or  has  holes inside the  exhaust  tapped?

Randy

  Dave I sent you a P/M...Bootlegger

Hi Joe


Do you have one that has been drilled? or  has  holes inside the  exhaust  tapped?

Randy

Randy,
 Both my OS Max S .35s have the holes inside the exhaust tapped.  Both have tongue mufflers, each of very different designs.  One is a fourty year old two piece tongue muffler and the other a contemporary tongue muffler.

By the way, will a stock OS Muffler for the .25 FP/LA cause an appreciable loss of power over the average tongue muffler?

Thanks,
Joe Ed

Two of the exhaust variations. And Venturie . Some late ones had the fancier one .

Randy,
 Both my OS Max S .35s have the holes inside the exhaust tapped.  Both have tongue mufflers, each of very different designs.  One is a fourty year old two piece tongue muffler and the other a contemporary tongue muffler.

By the way, will a stock OS Muffler for the .25 FP/LA cause an appreciable loss of power over the average tongue muffler?

Thanks,
Joe Ed

Hi Joe

A tongue muffler  will  not be  more restrictive,  the  most restrictive muffler  was the  stock  OS 703, it had a  tiny  exhaust hole, plus the  tongues  are  adjustable,  the  25  OS  stock muffler  for the  FP  or  LA  will  flow better than the  stock os  703,  The  best  flowing  lightest  tube  is  the  STOCK  OS  Jet Stream.
You also  must pay attention  to the  venturi  sizze when  you  switch mufflers, as  for  example   the  35S that came with a  703  had a venturi  larger  than .300,  mine  were .310 .  When using a  better flowing  muffler  you want to  use  a  .275 to .285 venturi

Randy

https://stunthanger.com/smf/classifieds-92/parts-ps-sets-cranks-cases-heads-os-st-magnum-royal-ops-etc/

There  are  many parts  for  the  OS 30 S  and  35S  here,  plus  I have  whole engines, both new  and  used

Randy

Did you ever see one of those centrifuge-type mufflers that were advertised in old magazines? If I am remembering the picture right, the exhaust would come in tangentially and "spin out" the oil from the gases. Maybe they had a drain line. Maybe there was a trap or a sump? I might try something like that if anyone ever got it to work. I forget what they called it and who made it. Was not advertised much, and I've never actually seen one.

If it worked, it would be the opposite of your "leaky Jetstream" and just what we could use....

Dave

PS--Now that I think about it, I think I know how to do this. I'd just need to get Scott to weld up the parts. No seams, no leaks!