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Engine basics => Engine set up tips => Topic started by: Bootlegger on September 04, 2018, 11:39:43 AM
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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
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Gil,
The guts of the two engines will interchange, but you will need the head specific to the
30 or the 35. You can get the case drilled to accommodate a bolt on muffler, also.
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'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
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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
The parts for 30 and 35 are identical, except for piston sleeve head and wrist pin, all else is interchangable
they use the same muffler too, strap on, and if the bolt on OS jet Stream, they need to have tapped holes inside the edge of the exhaust. Many people drill these all the way thru, then they fit the bolt span of an OS 25
Regards
Randy
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And except the head gasket.
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The parts for 30 and 35 are identical, except for piston sleeve head and wrist pin, all else is interchangable
they use the same muffler too, strap on, and if the bolt on OS jet Stream, they need to have tapped holes inside the edge of the exhaust. Many people drill these all the way thru, then they fit the bolt span of an OS 25
Regards
Randy
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
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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
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And except the head gasket.
Yep the head gaskets are different size, but the backplate gaskets are identical
Randy
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Dave I sent you a P/M...Bootlegger
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The muffler straps on not bolts on
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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
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The muffler straps on not bolts on
Yes & No .
A Jetsream , but its for a 60 . as I hadnt seen one , thought others might notve too , thus here it is .
(https://thumbs.worthpoint.com/zoom/images1/1/0216/11/vintage-os-max-jetstream-muffler-60_1_cfb5690c1d1ceca32a9fc09c3e303f1c.jpg)
Heres a 35 with a BOLT ON Jetstream ,
(https://static.rcgroups.net/forums/attachments/2/7/9/9/3/6/t5424133-248-thumb-1.4.13%20034.jpg?d=1357423076)
Incidently . Theres about FOUR Variations in the casting inside the Ex Port , fore & Aft .
Early , long core , tapped
Shorter core back in , tapped ,
ditto, untapped ,
and no cores for tapping- presumeably on later 703 strap on mffler versions . ( post 1970 , 30 & 35 S came out about 1964 )
ALSO , incidently ! The part No. for the ROD , LINER , PIN , PISTON are as for the OS H 29 R .
so a fewmore pics
(https://thumbs.worthpoint.com/zoom/images3/1/0316/20/vintage-os-703-muffler-fits-os-max-40_1_571d01b3a8b71fc45bf4d59d8df5fc86.jpg)
(https://thumbs.worthpoint.com/wpimages/images/images1/1/0916/20/1_23dd0ced7f3eb513eb6403c0b1f87aa5.jpg)
THISistheone with the sleeve etc interchangeable with the 30 S . timings 130/110 .
Further more & insofar ???
Theres a V similar H 35 C . NOTHING ( much ) is interchangeable with these & the 35S , so Dont Try . Except the HEAD , which is wedge . The 35S Hemi one will go on . unless you want a wedge 35S . :P
(https://static.rcgroups.net/forums/attachments/1/4/0/7/2/0/t9967978-223-thumb-DSCN2122.jpg?d=1492552679)
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(https://thumbs.worthpoint.com/zoom/images2/1/0511/15/os-max-35-cl-control-line-airplane_1_56738ee462f0c470a8c75327b2cc24c9.jpg)
Two of the exhaust variations. And Venturie . Some late ones had the fancier one .
(https://i.ebayimg.com/images/g/3TYAAOSw~Q9bJwQC/s-l300.jpg)
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The muffler straps on not bolts on
OS sold both strap on and bolt on mufflers for the 30 and 35S
Randy
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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
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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
Randy,
Thanks. I'll keep the venturi size in mind.
Joe Ed
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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
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The Jetstream muffler is also one of the best "castor oil mess distribution devices" ever conceived by the mind of man. Exhaust leaks out of every inch of the slit, unless you do something about it.
Brett
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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!