Help with 911 3.2 muffler bolts

[Wangan]

Hi all,

As topic states I've just purchased a Monty muffler and dansk cat bypass pipe. The hangers came without bolts and I was just wondering if anyone knows the correct size bolts in the areas if circled in red.

Since the muffler and bypass are stainless, I should be using stainless bolts also?

Thanks!

[HarryD]

Can’t help with the size but use stainless steel bolts and Silicon/Bronze nuts. This combo will not gall.

[917_Langheck]

If I recall correctly I used M8 40, along with a single flat washer and a split ring washer, all stainless. No galling with a dab of antifreeze on the threads. I've removed and reinstalled biannually with no issues.

The rusty hardware removed was 13mm headed, so M8 should be correct as I used the same size socket and wrench with the new hardware.

[ErrorMargin]

Originally Posted by HarryD

Can’t help with the size but use stainless steel bolts and Silicon/Bronze nuts. This combo will not gall.

Should the washers be silicon bronze or stainless?

Are these good options for the nuts and bolts? I’ll worry about the size, I just want to be sure these are the right types…

Nuts
https://www.mcmaster.com/product/91776A102

Bolts
https://belmetric.com/hex-bolts-10-9-m8x1-25-coarse-din-931-933/?

[john walker's workshop]

Where did you find the monty muffler?

[HarryD]

Originally Posted by 917_Langheck

If I recall correctly I used M8 40, along with a single flat washer and a split ring washer, all stainless. No galling with a dab of antifreeze on the threads. I've removed and reinstalled biannually with no issues.

The rusty hardware removed was 13mm headed, so M8 should be correct as I used the same size socket and wrench with the new hardware.

If you exercise the hardware frequently, like you are, galling is less of an issue. For those like me, that go this every 5-10 years, the heat cycles cause the to be officially yo remove.

All parts can be SS except the nut.

[HarryD]

Originally Posted by ErrorMargin

Should the washers be silicon bronze or stainless?

Are these good options for the nuts and bolts? I’ll worry about the size, I just want to be sure these are the right types…

Nuts
https://www.mcmaster.com/product/91776A102

Bolts
https://belmetric.com/hex-bolts-10-9-m8x1-25-coarse-din-931-933/?

You should be able to get both parts from any decent nut and bolt supplier.

[Wangan]

Originally Posted by john walker's workshop

Where did you find the monty muffler?

Just have one sitting

[Wangan]

Is there a reason against stainless nuts?

[na2ub]

Originally Posted by Wangan

Is there a reason against stainless nuts?

Yes. I found this out last year when I installed my muffler. Stainless bolts and stainless nuts tend to destroy each other when you torque them down, and get seized (gauled) so that they are super difficult to remove. I ended up just getting cad-plated hardware from Autozone, but stainless bolts and brass nuts seems like a great no-rust solution.

[john walker's workshop]

I never use SS hardware. Standard old cad plated stuff always worked for me. Just had to remove 3 SS bolts and nuts on a Carrera muffler. PITA.

[Wangan]

Wouldn't it be easier to use zinc nuts and bolts?
Yes zinc and stainless can cause galvanic corrosion, but the muffler will never really be wet.