Grand Rock mufflers?

[bevans6]

My local truck parts place doesn't carry Donaldson, they carry Grand Rock, which I have never heard of.  They seem legit;  http://www.grpipes.com/

Has anyone had any experience with them?  I am looking at their M-121 muffler, 5" in/out same end 10" by 15" oval muffler for my MCI with turbo 8V-71

Thanks, Brian

[luvrbus]

Brian, they have been around for 40 years you don't last that long building inferior products I have used their products before no complaint

[bevans6]

Thanks for the vote of confidence.  Made in Painesville OH, too.  $165 for a M-121 muffler, would probably fit most MCI's from the same kind of time period as mine.  Smaller than the OEM muffler by a lot, same height at around 10" but 15" wide instead of over 20" for the MCI, around the same length at 26" vs about 28" for the MCI.  Input on the MCI is 5" but the output was weird at 4.25" from memory.  I had to make a custom piece for the output when I built my exhaust three years ago.  I am going to put a 5" chrome tip on this one, just like the kids with the rattle cars have   

Brian

[TomC]

M-121 is the same number, and same muffler I'm using in my bus, but from Donaldson. I guarantee they are selling the Donaldson muffler. Good muffler, turbo rated, and puts out a nice tone. Good Luck, TomC

[luvrbus]

I never bought a muffler there but do buy a lot of the bellows pipe and they are made to your spec at Grand Rock they do sell the hump hoses for the air system if you need one their stuff is not junk