Max35 Engine Question

[JHildreth]

I acquired another Max 35 S recently.  The engine is used but in very good shape.  The case is a newer version that was designed with two tapped holes inside the ends of the exhaust port for attachment of a muffler.  The mufflers that I use have bolts entering from the back side of the case and made it necessary for me grind the raised fins off the back of the exhaust port to provide a flat surface for the muffler retention bolts.  In the process of doing this I noticed a hole in the center bottom lip of the exhaust port (see picture).  This hole goes completely through the lip and the drill might even have created a partial hole in the upper lip.  This hole is very clean and centered as if it were part of the manufacturing process.

Some exhaust gas will bleed through the hole with the muffler attached.  But, before I plug the hole with JB Weld, I thought I would ask if anyone knew what its function is supposed to be.

Thanks.

Joe

[JHildreth]

I guess it would help if I actually posted the picture!

[Joseph Patterson]

  Might have been for the baffle plate mechanism for those motors that were RC.
      Doug   

[Air Ministry .]

Theres a HOLE in trhe ENGINE .  J B Weld to the Rescue ) .

The ones with the threaded muffler holes , are the earlier ' Silent Flow ' type .

Then theres long boss ( there , undrilled , Short Boss , and NO Boss , so three or 4 casting variations .
The Strap on 703 dont need the retaining bolts .

Mustve been a cunning talented type to be able to get a decent drilling , in those parts .

[Gary Dowler]

Couldn't you fill those holes with a steel reinforced epoxy?   just adapted a K& muffler to a OS 30S that I have, using a clamp on system. 

Gary

[Dave Hull]

Joe,

Interesting. I have one 35S and two 30S engines, and none are like that. It would appear that the hole was a pilot for one of the head bolt holes. Are yours oversize? Sometimes the original holes stripped and guys went oversize to repair. I even saw one that was "reworked to improve it," wherein a guy upsized all the screws--even though they were not stripped--because "they needed to be bigger...." I don't know how anyone could miss the depth by a country mile, but rework specialists can do some incredibly unamazing things.

I can't see any reason that a dab of JB Weld wouldn't be an acceptable tweak. Or, if you like port priming these older engines (some like to be really wet) leave it open and get one of those 1 oz. syringes with the pointy 90 angled tip. You also might consider something that I have done on mufflers when I move the pressure nipple. If I don't have a correct thread screw (usually a M3x.5) to plug the original hole, I take a 1/4" long piece of o-ring stock and thread it into the hole. Cutting a diagonal slice off of it to get it started helps. Needle nosed pliers will let you complete the threading to a tight force fit. Then I just slice off the outside piece flush. You could do the same with a smaller piece of stock. Slice off the inside and leave a tail on the outside. That way it will never fall into the exhaust port and damage anything. I have not had one of these fail yet.

On the tongue mufflers I am using, the muffler is threaded, so I had to do the same thing you mention, spotface the case for the screw head to seat against. No issues. In fact, I have one more engine still left to do. Thank you for reminding me to get it done!

Best wishes,

Dave