Briggs Vangaurd 18HP Exhaust Mods!!

[snorth88]

Hi everyone, recently have done some mods to my stock exhaust on the Bigfoot:

-Removed restrictors from exhaust ports
-Ground out exhaust flanges slightly for improved flow
(discovered an exhaust gasket that was on backwards and was blocking 1/4 of the opening as well on the rear cylinder)
-Cut out tiny pipe outlet on can and welded in larger 1 1/2"outlet which will continue on thru 1 1/2" custom exhaust pipe

See pic for new outlet size comparison!! Its a lot larger....haven't got it back together quite yet to hopefully feel improvement

[jpswift1]

These engines are VERY restricted it seems. I remember following amphibiousdrew on a trail ride at night at Busco Beach and I could see his exhaust was glowing red inside the muffler. It was a brand new Briggs 18HP Vanguard with a brand new muffler all set up properly too. I think that some richer jetting will be necessary when opening up the exhaust a bit, but I'm not sure what number main to go with.......maybe someone can chime in.

[Tomo]

hi
Factory muffler modification also depends on the internal construction of the muffler . The chambers can number 1,2or 3 . How the exhaust flows from the primary engine pipes thru the muffler is critical . 90 degree bends , hole punched steel [no chamfer] are all bad for flow /performance .
Another version of modifying the factory muffler is
1st cut the primary pipes of the muffler . Typically u will have a 1 inch primary pipe around 4 inches long with an exhaust flange welded to it .THROW THE FACTORY MUFFLER AWAY
2ND
Have a machine shop machine up id 1 inch ,,od 1 1/4 ,,1 inch wide sleeve install on to primary pipes
3rd install either rigid pipe or flexi tube [1 1/4 id ]
4th 2x 1 1/4 adapter into 1 1/2
5th install muffler of choice

tomo

[snorth88]

Thanks I will keep these ideas in mind. Well see how it performs and sounds with these mods, If there are no improvements maybe I'll take it a step further!