Exhaust bolts, muffler to cylinder, locktite?

[redoakneck]

What about steel bolts in aluminum holes?? The aluminum expands differently than the steel, creating a thermal tightening and loosening effect???


What does the stihl manual recommend??

My buddy is a stihl mechanic and doesn't ever use any thread sealer, except silicone in the bar studs ( collar screws) .

He also builds racing motorcycle engines and knows his stuff.

I don't like using the goo, but will if that is what works.

I bet that part of the cylinder sees 500 degrees F

 

[Al Smith]

What about steel bolts in aluminum holes?? The aluminum expands differently than the steel, creating a thermal tightening and loosening effect???

Case it point Ford 3.7 V6, aluminum heads ,8 mm steel exhaust manifold studs but they do use a resistance nut .Nice collar nuts too if you run a tap through them to cut out the deformed thread ,I must have a hundred of them . The Bellville washer compensates for the thermal effect .--Google it .

 

[redtractor]

I've heard that you first get the engine up to temp and THEN tighten the bolts, while hot.

 

[angelo c]

What about steel bolts in aluminum holes?? The aluminum expands differently than the steel, creating a thermal tightening and loosening effect???


What does the stihl manual recommend??

My buddy is a stihl mechanic and doesn't ever use any thread sealer, except silicone in the bar studs ( collar screws) .

He also builds racing motorcycle engines and knows his stuff.

I don't like using the goo, but will if that is what works.

I bet that part of the cylinder sees 500 degrees F

Many Cyl head bolts come thread "locked" of some sort from factory. grey looking stuff.
I use thread "sealants" on muff more then "locks". I have a fear of rusted out exhaust bolts...comes from the days watching the AP's at the local airport remove turbos ...eek that gives me nightmares.

 

[Lone Wolf]

Well the Stihl repair manual says to use Loctite high strength 649 on the muffler to cylinder bolts.

 

[redoakneck]

Looks like that locktite 649 is a European product???

Lots of good ideas here, maybe I just had a weak spell??

 

[srcarr52]

Use high temp RTV silicon on the threads of the bolts into the cylinder and it will keep them from backing out. It's an old trick to keep manifold/header bolts from getting loose.

I also ditch the gasket (if it has one) and use high temp RTV, it will keep you mufflers from fretting up the gasket surface on the cylinder.

 

[Zombiechopper]

Looks like that locktite 649 is a European product???

Lots of good ideas here, maybe I just had a weak spell??

looks like red 649 is euro product. It's red high strength, high heat. The equivalent north american product is loctite 272 as near as I can tell.

I'm in the same boat as the guy that said he's more worried about them seizing. I've never had a muff bolt loosen. I put em in tight and they come out hard as fark when I've torn em down again. If anything, I'd use anti seize compound not a threadlocker. Steel and aluminum like to stick. But hey, that's just me and my experiences.

 

[redoakneck]

Well, got a break at lunch, went to the hardware store.

86-87mm bolt, only thing they had that I wouldn't have to shorten was a chrome 90mm. No big deal to shorten, just takes longer and I'm on lunch wanting this done. Paid $6.79 a piece for the chrome Harley bolt, not worth my time for the extra 10 bucks, plus they look cool.

So, drilled the bracket, muffler, gasket, and heat shield out to 6mm. Tapped the cylinder, and used ultra copper ( was the only high temp my buddy had in his shop), which can be taken back apart.

Will wait a day to start, run, and get it hot. Then I'll re- tighten.

The bolts cost half as much as the whole muffler, but saved me time and they look good, not that I care on a saw. Chrome should tolerate the heat and hopefully not rust.

I know, I know, pictures, was rushing so only thing to take pic of is the fat chrome heads sticking out of the muffler--- good reminder for me to check the dern things after a re- build.

 

[redoakneck]

Pics

 

[redoakneck]

Pic

 

[redoakneck]

Reason I tore it apart was to put hda-199
Carb on it

 

[redoakneck]

At least if those get really tight , they have large heads on them to get a better grip on!!!

 

[redoakneck]

I bought this saw from Neil Murphy 3-4 yrs ago, has been loaned to a tree service friend of mine, used and abused, finally getting some love with them fancy bolts and new carb !!!

Wasn't anything wrong with it before, just wanted to try the bigger carb because I had one sitting there on a 359 carcass.

 

[redoakneck]

Splurged for a new air filter too.

 

[srcarr52]

I wouldn't retighten after warm, just leave the high temp RTV alone. Also, Ultra copper is some of the best high temp you can get.

 

[redoakneck]

10-4 on the no re-tightening!!!

I did put a new 44.3 mm caber ring in it too, just because.

 

[Al Smith]

Nearly 7 bucks a bolt? Wow!

 

[redoakneck]

Nearly 7 bucks a bolt? Wow!

My hiney is still smoking!!

 

[Lone Wolf]

PicsView attachment 16264

Looks like you have room to safety wire those.