I recently purchased a new RB system . The only part im.missing is doughnut gasket 1757-40-356 . It is NLA and I don't have one on my current set up. I purchased a used 79 system but the guy who sold it to me lost / threw out that part .
Does any one know of an alternative or how they solved the issue ?

 

if you know the inner diameter you could probably find one that works. Hondas use these more than Mazda

 

I have no idea what it is and have no way to measure it .

 

I had the same exact problem on my 79. I finally found a regular gasket that sorta fit and used exhaust gasket maker to seal it up best I could.

 

what gasket did you use ?

 

No luck today searching

 

I believe that exhaust is a 2.5" od. I looked up 2.5" od doughnut exhaust gasket on Google and lots of stuff came up. You can measure the flange on the exhaust to see what one would fit. Just use a tape measure. As said lots are listed as Honda and even Subaru parts.

 

Many of the exhaust gasket's are NLA now. This one is an all metal donut that shouldn't really wear out. Here's a pic with dimensions to find one similar. Or, if you know someone with a lathe, they could turn one pretty easily. The hard one to find is the rubber donut where the air pipe connects to the muffler. (2090-40-508A)

 

This is perfect !
I can have one made now with those specs .
Thanks Banzai .

 

Check out this PDF

2.265 is about 2 1/4"
1.6" is 1 3/5th

https://www.walkerexhaust.com/conten...%20Flanges.pdf

 

I took a mid pipe to a few auto parts stores and checked for best fit.
A muffler shop might be a good source too.

 

this was a source of a gasket i need many yrs ago.

 

For now I think I have a solution Thanks guys . Spent fhe whole day polishing the mid pipe . No more rust!

 

muffler cement <-----looks like it would work?