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View Full Version : OT - Exhaust curiosity on a B&S Vanguard



Joel
02-20-2008, 06:12 PM
I am doing some work on the 18 hp Vanguard motor that drives the pump on our brush truck. When I took the exhaust off, I noticed a thin, split sleeve in the exhaust port. It is held in by the muffler flange and appears only to reduce the diameter of the exhaust port where it enters the muffler. The small motor shop in town could only guess as to their purpose - B&S calls it a "port liner" part #691493.

Why are they there and should I leave them in?

pcarpenter
02-20-2008, 06:24 PM
I would guess it prevents erosion from hot exhaust gasses on what is probably a bare aluminum head. It may also help with the seal between the manifold and port....effectively a tube that crosses the potentially leaky junction. Exhaust leaking at a flat flange will eventually erode even cast iron.


Just a guess though.

paul

Racerx
02-20-2008, 06:57 PM
pcarpenter is exactly correct. If the exhaust gaskets were to ever start leaking, the hot exhaust gasses would rapidly melt the aluminum head if those liners weren't there.

wierdscience
02-20-2008, 11:29 PM
I had a Vangard with the same setup,a thin sleeve past the flange and as the others said it protects the flange seat and seal.The port on mine also was tapped 1"-npt female to accept a screw in muffler.

Joel
02-21-2008, 12:16 AM
Thank you gentleman, and thank you too wierdscience.

Interesting, not what I expected. To be assured of clarity, the sleeve does not bridge the exhaust joint - it slips into the port and stops flush with the manifold flange.
So I am supposing that the consensus would be to leave them in?

Fasttrack
02-21-2008, 12:30 AM
Yes leave it in - that is common on many small engines although they usually bridge the gap. Often you will see them used to keep the exhaust gasket in place on the muffler. The sleeve then slides inside the port when you assemble it. To replace the gasket you have to compress the collar and remove it from the muffler. This is how all of the 6000 series single cylinder engines are made anyhow.

wierdscience
02-21-2008, 12:37 AM
Thank you gentleman, and thank you too wierdscience.

Interesting, not what I expected. To be assured of clarity, the sleeve does not bridge the exhaust joint - it slips into the port and stops flush with the manifold flange.
So I am supposing that the consensus would be to leave them in?

Humm...not a gentleman?Must be a scholar:D

Sleeve could also keep from burning out the flange weld on the craptacular mufflers that costs more than one for a car.

Joel
02-21-2008, 12:56 AM
It goes without saying.
Just don't forget to wear your 'scholar' hat. :D


http://img.photobucket.com/albums/v186/JoelinTX/CapLarge.jpg

wierdscience
02-21-2008, 02:02 AM
It goes without saying.
Just don't forget to wear your 'scholar' hat. :D


http://img.photobucket.com/albums/v186/JoelinTX/CapLarge.jpg

That's not a scholar's hat,that's an AGGIE thought cloud:D