tail pipe hold-downs

[John Fitzpatrick]

Rather than cut out and weld supports to the mufflers, I’d prefer to use the spring hold-down type similar to these in this photo posted by JerryD. of his very nice Mk II.

http://www.gt40s.com/gallery/index.php?n=353

Is there a source(s) for these, or are they custom fabricated?
John

 

[Bill Musarra]

The springs look O K, but you have a lot of heat that can eventually make them brittle, not to mention they will scratch up the surace of the muffler with all the vibration. If you go to just about amy muffler shop they should have a bunch of T clamps made of stainless just laying around. They can be adapted quite easily. You can either weld them to the frame or fix them so they only clamp to hold.

Bill

 

[Ian Anderson]

I agree re the scratching

Used to drive karts and they used the spring system to hold on the silencer and under the springs and around the supported piece would be shiny after 1 race meeting (HT exhaust painted previously)

Nice talking point though!

Ian

 

[Lynn Larsen]

In terms of them actually doing anything, I just can't see how they could do much, if anything, to restrict the movement of the exhaust. I would be afraid that they would become a source of vibrational noise as well.

SS T-clamps would look good and work. So would properly sized u-bolts and they could be either SS, chromed or sent to be coated along with the exhaust.
SS, while it takes some time and work, polishes nicely and retains its polished luster quite well to boot.

If you made a support from a tubing whose ID was ≈ OD of your exhaust and then line it with pieces of silicone cloth (header wrap) the braketry could be finished as described above for the T-clamps or U-bolts. Either way you'd end up with something aesthetically pleasing, functional and non-marring.

Lynn

 

[Rich]

True Value Hardware has a good slection of springs. One spring hooked in the center, in addition to the ends, works well. The idea here is to allow the mufflers to move due to heat expansion. Any marring of the stainless surface by the springs will be minimal and you will never notice it under the springs. If heat should get to the spring after a while, replace it. 2 to 3 bucks each is manageable.

 

[Ted Reese]

The point of the springs is to allow expansion. If your exhaust and headers are constrained they will eventually crack.

 

[Ian Anderson]

Point of springs is quick release / ability to change.

I believe the originals had loops on the primaries and collectors and then collectors to secondaries

Pair of pliers, couple of springs off remove pipes - access to sispemion, box etc much quicker.

Ian

 

[BenL]

The point of the springs is to allow expansion. If your exhaust and headers are constrained they will eventually crack.

If the perch for the exhaust is secured to the chassis, would you have to worry about the chassis and the engine vibrating at different rates if you used a solid connection method instead of the springs?

 

[Ted Reese]

If the perch for the exhaust is secured to the chassis, would you have to worry about the chassis and the engine vibrating at different rates if you used a solid connection method instead of the springs?

Yes. Most cars have some sort of rubber isolation mounts for the exhaust. This is to allow expansion, twist, vibration and general movement. The springs allow the exhaust to move a little in the mounts. This is also true for slip fit exhaust pipes with springs holding them together. It allows for the movement.
As Ian pointed out it also makes for fast assembly and disassemble of the exhaust.

 

[Howard Jones]

Attach the mounts to the gearbox. This will allow the entire assemble, engine, gearbox, exaust system, to move together as the engine shifts around under torque loading. Much less stress on the various mounts, header welds, etc.

 

[Lynn Larsen]

Howard,

That is exactly how mine are done. On the G50 what used to be the transaxle mount makes a perfect place to attach the exhaust bracketry.

Guys, I'm maybe dense, but about the only thing I can see those springs doing is keeping the silencers from falling on the ground if everything else was unhooked; unless, those springs are a LOT more stout than they look in the picture. But, what ever works for you is cool for me.

Lynn

 

[John Fitzpatrick]

Okay, from all you guys have said, I think my best option is to fabricate a support piece that attaches to the transaxle and cradles the mufflers from below and uses springs to hold them down snug.

I've been trying to locate the sort of band clamps that were used in the photo posted above to clamp the primaries to the collectors. With singular lack of success. Does anyone know of a source for these?

Thanks for the feedback gentlemen, I appreciate it.
JD

 

[Rich]

No clamps were used John. They are a slip fit and held together with bolts that go through welded on lugs.

 

[John Fitzpatrick]

It's tough to make out from the photo-- are the primary and collector pipes the same size and the sleve there to allign and seal the joint? Very sanitary look.

 

[Rich]

Here's a closer look John.

 

[Bill Musarra]

I orginally wanted to use the springs and started out with this arrangement in the first photo. After I got my mufflers, the shop guys showed me the stainless Tbolts and I have since changed my mind and am going to use the slip fit like Rich's on the front and attach the T bolts obtained from the mffler shop at the rear with a fabed bracket mounted like the one I started with on the inverted base. You can also use the Tbolts that have a base on them like the ones that come with the Accusump as seen in the side pic. Its all a matter of alignment. All shown here has been removed, cleaned up, and ceramic coated. Just awaitng reinstall. If you are going to use a heat shield there are lots of ways to do it. Here is one. I think it is Neals and is a neat arrangement.

Bill

 

[Russ Noble]

The point of the springs is to allow expansion. If your exhaust and headers are constrained they will eventually crack.

Generally race applications mainly, so the pipes are free to vibrate without stressing the relatively lightweight, solid mounted supports which would otherwise crack and break, leading to rapid failure of the whole (now unsupported) exhaust system.

Solid mounted clamped suppports will crack or if they are really beefy then the exhaust will crack as Ted said.

For the road I would definitely go with a reasonably substantial, flexible, transaxle mounted, clamp system. IMHO

Cheers

 

[Bill Musarra]

I guess I should have added that they need to be rubberizzerd for flexibility. Since they are Tbolts, they act like nylocks, so don't have to be tightened down. No give is bad when we are talking about the amount of vibration encountered with these setups.

Bill

 

[John Fitzpatrick]

A lot of great ideas here! I've ordered a pair of Gibson Superflow race mufflers, so I'm off to the shop as soon as they come in. I'll post a pic when they're done.
Thanks for the help.
John

 

[Bernard]

As the large GT40's member majority I am partisan to fixe exhaust pipes with springs. This mounting allow as well vibrations as dilatation movements to prevent any crack.
http://performanceweldingheaders.com/img/springtabkit.jpg
If you are using this kind of spring, don't forget to pass a safety wire as a loop inside the spring to secure it. This will avoid to lose a piece of spring in the track if for any reason the spring breakes