Possible to Block One Outlet on a Dual Exhaust?
 

I have a GHL "1 in 2 out" muffler on my car. I have a love/hate relationship with the exhaust - I love it and my wife hates it. Actually it does sometimes even get on my nerves especially on longish drives on the highway.

I have read about some people who have capped off one of the outlets to quiet the muffler a bit, but I am concerned that this could harm the internals of this expensive exhaust. Does anyone know the internal plumbing designs of the GHL's? It stands to reason that if there is only one inlet and two outlets, capping one outlet SHOULD simply route all the exhaust flow to the point of least resistance.

I would like to have the best of both worlds by having some sort of cap that I am able to "hot swap" for the old outlet. This way I can run it as is when I am either at the track or buzzing around town and then cap it off if the wife is with me or if I am on a long drive. I have a friend with a muffler shop that can likely do this part quite easily, but I am still worried about causing internal damage to the muffler.

Thanks.

No problem.
You could go the cheap way and use a heavy guage soup can with a muffler clamp.
You could also fab up a cap like the early cars with three outlets have. Do a search for sport mufflers for pictures.
I have a Flo-Pro muffler and have one side capped off but I had mine crimped shut and then welded. I don't like the sound of two outlets on m y car.

Yes - I have seen the posts about soup cans. I have actually tried to fab one of these up, but I cannot seem to find a can with the appropriate diameter. Regular Campbell's is too small and Chunky is too big. My outlet pipes are 3" diameter.

So, this capping method will not cause any internal damage to the muffler?

I recommend you rummage around a Home Depot / Lowes and see what you can find. I think you'll find something there that will suit your purpose.

Why not have a shop cut one of the outlets in half and weld on two flanges with a block off plate that can be inserted or removed as desired. That's what I'm going to do with my stock muffler that has a second outlet added on last year. It gets a little to loud for the wife with both outlets open. Although sounds great to me.

Interesting idea - I will suggest that to my friend. One question though - how would a plate seal itself betweent he flanges?

Also, does it matter which outlet I cap?

Thanks.

I have a M+K 2 in 2 out muffler and Ben ( the owner of M+K ) also makes a "cap" for his mufflers. But instead of going over the outside of the tip it goes inside. The cap has a nut welded in the inside so you slide the cap in,mark the tailpipe and then drill a hole. You then install the cap and hold it in place with the bolt nice clean install. When at the track or when I want to get loud I remove the bolt,slide the cap out and voila!! I did have to file/sand the O.D. of the cap to fit correctly but no big deal with a belt sander.

I have to block off one side when I use the LM-1 otherwise I get a real lean reading..

Tuna fish can seems to be the right size for my borla.:D

I would prefer a "doughnut" ..... a ring of metal , either solid or formed with a lip...that slips inside the offending right side outlet. You can experiment with various internal hole sizes for the doughnut to get the sound you like ( maybe even closed up...no hole at all).

If made of formed metal with a "L" shaped ledge...then tack weld a backing nut on the small, contacting edge of the "L" and drill thru the outlet to mate up. A bolt can be used to attach / detach the doughnut.

If made from a sold bar ( disc), then the disc can be radially-tapped for the appropriate thread to mate with the retaining bolt...

- Wil

I have a Borla quad out, and I had a cap fabricated to block off the pass. side. On hte inside of the cap I layered a high temp rubber to ensure a tight fit. It is removeable and works great. No more ressonance ance still sounds awesome. Good Luck.