Mufflers with cap on Crossover Pipe exits

[ecsjr]

I had no luck searching for this,  so starting a new topic.

The mufflers on my '73 Eldorado have caps over the crossover exits.

I am sure there are differing opinions on whether to have the crossover pipe or not, but what are your opinions on capping mufflers that must have been designed to have the crossover pipe installed?

I plan on putting a crossover pipe on,  the right choice?

Thanks in advance, 
Ed

[fotoguzzi]

that is strange.. I've run a 1100cc Guzzi without a crossover and then put one in, didn't really notice any difference.

[rodekyll]

The crossover point defines the exhaust length.  The area ahead of it has one set of pressure and flow characteristics for each pot, and the area behind it acts as a common expansion and scavenging area.  Placing it in different locations along the head pipes as Guzzi has done over the years changes the length of the forward area and is supposed to help tune the air flow through the engine.  Removing the crossover does that too -- effectively relocates it to behind the mufflers and eliminating any plenum or scavenging effect.

That being said, I've run the same bike with the crossover between the heads, near the engine bottom, under the transmission, and removed entirely.  I gotta say that except for no crossover, the only times I notice the difference is on initial roll-off and WOT.  In my normal operating rpms I'd need instruments to tell any difference.  When I had no crossover I felt the bike was restricted at all rpms and also that it tended to ooze a little exhaust out of the slip-on joints.  It wasn't a lot and I don't know that you'd notice unless you were actively tinkering with different configurations and comparing them.  An interesting comparison is to hang dryer sheets behind the mufflers and comparing how much the exhaust flow deflects them at different rpms.

[mtiberio]

I hate the stock loop crossover with a passion. I had a bunch of Stucci mufflers break at the crossover stubs. I have been running Epco mufflers for years since, and I never installed them with the Epco crossover (solid). Years ago I switched to some of that Stainless Steel flexible tubing (spiral wrap) you see on old Indians and Harleys, etc. It allows the muffler to find its own sweet spot, and doesn't lock the 2 mufflers across the bike into an orthogonal relationship (good given Epco's quality control). One side benefit of the flexi crossover is I can simply loosen the left side muffler at the head pipe, remove the one mounting bolt, and let it sag so I can remove the axle. If you have a hard crossover, you end up having to loosen the crossover clamps, and partially unslip more parts, making realignment a pain. Some day I will go no x-over at all. It is still a pain, and I don't like having to remove the muffler pair as a unit when I do serious maintenance. By then my last set of Epcos will develop an internal death rattle, and I'll probably go with no crossover Ram-Flows... Yes, I expect it to be a bit louder, and to lose a bit of torque, BFD.

[Antietam Classic Cycle]

In my opinion, keeping the crossover on Loopframe Guzzis is a good idea. Mainly because of the extra stiffness it adds to the exhaust assembly. Loops are known for having loosening issues with the header nuts, without a crossover the weight of the mufflers can have them "waggling" back and forth on their mounting bolt, moving the headpipes with them and helping to loosen the header nuts. The factory headpipe-to-frame straps help control this movement, but don't eliminate it entirely.

Do take care during assembly to have the mufflers parallel to one another. This may require washers/spacers between the frame tab and muffler mount. With the mufflers parallel to one another, the crossover should be an almost perfect 90* angle to them. This keeps stress at the crossover "spigots" to a minimum and helps prevent cracking there.

[ecsjr]

Thanks for all the feedback.  Maybe the stress-related cracking was why these are capped - and these mufflers are in great shape.  Of course, I don't know how old they are.

I think I will put the crossover on this summer.

Ed