Side Pipe Mounting

[Turk]

If the side pipes are mounted directly to the frame, aren't they subject cracking and stress.

On my ERA the pipes were lined up so to accept a rubber connector between the pipe mounting bracket and the frame. At one point due to misalignment even that broke in half.

On my current car the mounting bracket aligns perfectly with the frame, thus NOT allowing any room for a rubber bushing or such.

I would appreciate any input on this. How are you guys doing it?

TURK

[Cobra20646]

Turk,

Solid or flexable motor mounts?

[Turk]

Motormounts are rubber.
Big,thick and black.


TURK

[RACERAL]

you may want to make a "step down" bracket to go under the body/frame and then mount to a rubber bushing.. I know what you are into.. I just mounted mine in rubber...

[Rick Parker]

Yes Turk do not mount them solid. There must be allowance for some compliance due to the engine "torquing over" otherwise all of the twisting is forced into the tubes and or the mount. The weakest link will fail repeatedly. Maybe 2 struts from the muffler with rubber sandwiched between it and the mount on the chassis? Personally I used 2 pieces on each side of the car near the exit of the muffler of 1 1/4" wide X 2" long channel (shaped like a "C") stood on end & welded to the chassis. Then the strut from the muffler had a 3/4" hole in it for a round rubber bushing that sandwiched the strut then it was slid in between the two legs on the chassis and a 5/16" x2" bolt went through both legs and the bushing in the strut. If you need a real good pic let me know.

Rick

I need paint help!

[RallySnake]

Turk,

I fought this problem for years. With rubber engine mounts, I was always breaking something. Usually the header tubes would crack and the rubber sidepipe mounts kept breaking, too. When I rebuilt my engine, I had it very carefully balanced with the harmonic balancer, flywheel and clutch. At Ron Butler's suggestion, I run solid motor mounts.

I used 2 angle brackets for each sidepipe. Each one is 1" by 1/8" in cross section. The driver's side rear one broke a couple of times due to a hole I drilled in it to dissipate heat before it got to the frame. I made a slightly larger one that is 1.25" by 3/16" without holes. I made it to Texas and back and have run three rallies without another problem. I was worried that the solid engine mounts would cause the car to vibrate. They don't.

Paul

[ST]

Turk
Kris told me you were thinking of using rubber bushings but you don't need them. I haven't heard of anybody breaking a set like we have and besides....it's not like you don't have extras.

[bmalone]

I run solid engine mounts and solid pipe mounts.

[Turk]

Here is to further complicate the matter.......

If the engine is solid mounted to the frame, any amount of torqueing, moving, shifting is going to be along with the frame itself.

So the the pipes, the frame and the engine are all moving in unison, I can see how they would stay together. However when the engine itself is mounted on rubber engine mounts, the frame itself stays put, and the engine moves while the sidepipes are securely held together.
Is it safe to say, if the engine is hard mounted the sidepipes should be as well?
Or, if the engine is on rubber mounts so must the side pipes?

TURK

[RallySnake]

Turk,

Think about it. If the engine is on flexible mounts and rocks side to side just a little, say 1/8th inch, the headers act as a lever on the side pipes, and thay are going to have to move up and down too, maybe 1/2 an inch. I was not able to find a way to let the sidepipes move that much without sagging down from the weight, heat and vibration and cracking the header tubes. That's why I went solid all the way. Except for the transmission mount. That needs to flex to let the chassis twist.

Paul

[Excaliber]

I re-mounted my side pipes solid to the frame. ONE race and I cracked the headers.

Ernie

[RallySnake]

Ernie,

Do you have solid motor mounts?

Kris,

Jump in here any time!

Paul

[Excaliber]

Rubber motor mounts, BUT I had a metal bar that bolted to the motor and the frame, another bar the bolted from the header collector area to the frame. The rear of the side pipe was then bolted solid to the frame. So I'm thinking, "OK, aint nothing moving ANYWHERE, I got it ALL solid now!" Trans mount was rubber and left alone.

It was kinda cool at first, I could feel the body (in my seat) "torquing" when I would "load" the motor. It vibrated the car too, didn't feel comfortable driving, but that was kinda "neat" also, like a "bad ass" Cobra thing.

I suspect the "vibration" is what cracked the headers just above the collector where the four tubes come together. I had it welded and took off all the support "bars".

.....back to the drawing board.

Ernie

[scottj]

Regardless of the type of motor mounts, when the chassis flexes and twists, the relationship between the mounting points changes (those points being the header to head and the sidepipe to frame). The harder you drive the more the frame twists and the more the pipes are stressed.

Rubber mount the sidepipes and there's a place for some "give".
Solid mount the pipes and the pipes do the "giving".

[RallySnake]

I've put over 100K miles on the beast. I made my own headers and sidepipes. I've tried several types of flexible mounts. The only ones that work are really solid anyway.

Ron Butler has built more Cobras than anyone I know. He worked on the original race cars during the heyday of the Cobras. Every tip he has given me was been right on the money. Including, use solid engine mounts and solid sidepipe mounts.

Paul

[PatBuckley]

Turk -

Take into account the fact that your primary pipes are not bolted solidly to your side pipes....there is a certain amount of flexing that can take place there.

You don't have flanges - you use weld tabs and bolts to hold them together.


pb

[RACERAL]

if you go rubber , go rubber in all 3 points.. if going solid go solid in all 3 points....never run a rubber motor and a solid trans mount

[Janusz]

Here's a side pipe mount from the "Butcher's" JBL Cobra web site.

http://www.cobralads.com/butcher6.html

No sure how much flex/support you get from the back supports, plus the bands are quite visible.

[boxhead]

Another idea that may work is to use the flexable pipe as used on a large range of factory vehicles, ie Nissan Patrol.
I dont know if it would work or not it was just a thought.
I have also seen convolluted type exhaust pipe.

[Ant]

I personally think solid mounting isnt the way to go, solid mounting is a quick way for some people who havent got the time or whatever to design a proper mount!
I know a guy who rebuilds very valuable classic racecars and he said they are high maintainance with everything designed light and rigid, and parts do fatigue more often due to the stresses and limited miles they do, but they are race cars and solid mounting can give quicker lap times, and as Colin Chapman said as long as they break after the finish line!

My engine uses a sleeve welded to the engine bracket 1/4" thick steel cutout , I use poly flange type bushes, that have a metal sleeve pressed into them for the 1/2" mounting bolt, and engine plates attached to the chromemoly chassis upright, this setup has some compliance and there is no detectable movement, the same with the sidepipes the rubber type mount needs to be designed so it actually supports the muffler etc, so it might be better to have it under compression.

Mounting an exhaust solid is okay if the engine doesnt move, but on race cars they are often held on lightish supporting brackest with a spring or suchlike holding them to the bracket so they can move a bit with flex or heat change. My experience with solid mounting the mufflers resulted in a cracked exhaust manifold.