Silencer thru-bolt specs?

Dec 28, 2003 5 Replies

Does anyone know of the specs for the bolt that runs through the silencer of my Irvine 39? It's the same width / thread as the 2 bolts that hold the silencer to the engine. Looks like 145mm long, 3mm thread? (I'm not sure if they're metric or not).



I broke mine!



Cheers,



Jim


Long muffler bolts typically sell for $4-$5 apiece...

An easy fix is to get a 12" length of 4-40 all-thread rod. Dress one end with a flushmounted 4-40 locknut w/ nylon insert. Hit it w/ a drop of thin CA, and rough-cut to length. Run a 4-40 tap thru the back half of the muffler, then assemble. Put another 4-40 locknut on the aft end, and whack off the excess rod with your Dremel...

I've done this to many old OS mufflers, and it holds...

Cheers,

Bill

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'Toggle bolts' are another cheap source of long bolts. Sometimes called 'drywall anchors'.

Mike

Not much help in the UK, but many swimming pool pump motors in the US use a good screw that I have used to replace the long screw in the GMS mufflers. Check with motor rebuilders for an appropriate length one. They will be made of better wteel and higher tensile strength than the average hobby stuff. You can drill out the muffler and use a good lock nut on the end.

Those are usually very soft, cheap metals that end up with the heads snapping off. I use pump motor bolts.

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