Sidepipe mount fastener issue

[Glenview289]

Brian and I agree with Dave and Geary, bolt them up and forget them. Being two engineers, we would have jumped at the idea of making something more complex than it needed to be, but the fact is, it works as designed! One tip, just make sure the engine, headers, and drive train are all bolted down securely in their final position before mounting the side pipes. Mount the side pipe to the collector, there is a slight amount of play in the 3 bolts to adjust for your desired position. Place the mounting brackets on loosely. Tighten the collector first, then before you tighten the mounting brackets, make sure each bolt is free in the mounting holes to the pipe and frame. Do not push on the side pipe to match up to the bracket! This will put a side load on the mont, and the constant pressure will work it loose over time. Some elongating or opening up the diameter of the bracket holes may be required. Tighten everything down and you are good to go. We have 4K miles and a few track days, and the side pipes have not moved or become loose.

Bill

[davids2toys]

The guys who are just bolting it up, that's great and I have all the respect for the knowledge and opinions, but I would like to know why it works and does not crack out when providing no flex in a system that is flexing all around the mount...if everything was solid mounted, then I would totally understand. So can you inform the people who have chosen the flex route why it is OK to solid mount.
Also, I did not build my car so I had no control in setting up the collecter/header combo. I have gaps on both sides and they are different from each other, the flex I am providing is not that much, it is really more of a cushion than anything else. I don't think this could possibly cause a crack as a few have suggested. I searched for the threads about providing flex causing cracks and could not find anything
Anyway, I have attached a few pics. The bracket with the small gap is the passenger side which I have not done yet, this is a very small gap. The small round bushing is from a piece of fuel line, it goes in the bracket hole and the bolt goes thru it. I will no doubt use the smaller length bolts on the Passenger side because of the smaller gap. I ended up with the spring being about 1/2 way compressed. The blue color on the spring is lock-tight.
Dave

[mkassab]

Nice set up..... while direct bolt-up may be fine, I have to believe this is as good or better.

Mark

[K.Wilson]

I used a piece of .090 thick gasket material between the frame and the bracket so I would not have metal to metal contact then I bolted it down just like the Weavers say to.

That was in 1993 (OMG that is 17 years ago) and I have never had a problem. Although it may not seem like it, there is quite a bit of "flex' in the side pipes/headers that is more than enough to accomodate the "flex" in the engine mounts.

Keith

[davids2toys]

I used a piece of .090 thick gasket material between the frame and the bracket so I would not have metal to metal contact then I bolted it down just like the Weavers say to.

That was in 1993 (OMG that is 17 years ago) and I have never had a problem. Although it may not seem like it, there is quite a bit of "flex' in the side pipes/headers that is more than enough to accomodate the "flex" in the engine mounts.

Keith

The Weavers actually said no rubber at all. Also, .090 is not.250 or better, some guys even reported 3/4 of an inch. I cannot believe it would be a good thing to just close this gap up with a bolt. I build helicopters for a living and we don't pre-load anything at all, if it has a gap, we shim it!
interesting about the flex in the pipes though, I did think about that but decided this was the safer way because I don't know how much flex is in the pipes and I am not an engineer so I can't figure it out. I wonder if there is a way to figure it out..I'm sure there is, but not for my little brain!

[davids2toys]

Nice set up..... while direct bolt-up may be fine, I have to believe this is as good or better.

Mark

exactly

[RJacobsen]

The bracket with the small gap is the passenger side which I have not done yet, this is a very small gap.Dave

The flange on the side pipe can be tweeked to increase that gap. you can probably do it on the car if you can get something on it to give it a bend.

[Glenview289]

Dave,

"......I would totally understand. So can you inform the people who have chosen the flex route why it is OK to solid mount."

Because it works! The three replies with solid mounts are 2 BB & 1 SB engine with a wide range of HP and 2 different ways of mounting, all without issues. I guess I would reverse the question to "If you are having an issue with nonstandard flexable mounts, why would you not want to go to the as designed hard mounts?" Your helicopter experience has shown you to shim gaps and bolt up solid, that is exactly what we re doing with solid mounted side pipes. Remember, if you let it move, it is going to move. As mentioned above, the side pipes do have some flex, as well as the frame itself. Solid mounting will get everything moving together. If I were to go to a flexable mount, it would probably look similar to what you came up with, except I would probably go with studs welded to the frame as Rod suggested and bolt it up to the rubber spacer and leave off the spring. I cannot see how the springs would stop the torque of a 500 HP of engine from deflecting unless they were condiderably heavier. I know how irratating it is to deal with persistant issues on the car and wish you well with your fix. Update us after your road tests.

Bill

[davids2toys]

The flange on the side pipe can be tweeked to increase that gap. you can probably do it on the car if you can get something on it to give it a bend.

Not really an issue so I won't bother, thanks though.

[davids2toys]

Dave,

"......I would totally understand. So can you inform the people who have chosen the flex route why it is OK to solid mount."

Because it works! The three replies with solid mounts are 2 BB & 1 SB engine with a wide range of HP and 2 different ways of mounting, all without issues. I guess I would reverse the question to "If you are having an issue with nonstandard flexable mounts, why would you not want to go to the as designed hard mounts?" Your helicopter experience has shown you to shim gaps and bolt up solid, that is exactly what we re doing with solid mounted side pipes. Remember, if you let it move, it is going to move. As mentioned above, the side pipes do have some flex, as well as the frame itself. Solid mounting will get everything moving together. If I were to go to a flexable mount, it would probably look similar to what you came up with, except I would probably go with studs welded to the frame as Rod suggested and bolt it up to the rubber spacer and leave off the spring. I cannot see how the springs would stop the torque of a 500 HP of engine from deflecting unless they were considerably heavier. I know how irratating it is to deal with persistent issues on the car and wish you well with your fix. Update us after your road tests.

Bill

Bill i do see some of your points for sure. But the bolt it up guys are not saying anything about shimming, if you just bolt it up you are preloading the part, that is a bad thing, unless you are talking about a torsion bar which we are not. So the guy with the 3/4 inch gap should just put a bolt in and go for it? Sounds like a bad idea to me, that, at a minimum, needs to be shimmed in its natural state.
The springs I have are not meant to stop the torque, just cushion it so it provides a little flex. as i said, they are already 1/2 compressed.
I do disagree on the point when you saying everything is moving together mounted solid...your way they would not be moving together, my way they are, this has been my point the whole time.
Your way: motor mount(flexible), Tranny mount(flexible), side-pipe mount(solid and preloaded, NOT Flexible)
My way:
Motor mount (flexible), tranny mount (flexible), Side pipe mount (flexible and not preloaded)
Also, as I said, I am not an engineer so you may be correct in all you say, but some of us are just not to comfortable with it and just don't understand the "do it because I said so" with not much of an explanation approach. No disrespect intended!
The only reason I am doing/re-doing it is because it was done poorly in my opinion by the previous owner and the bolts vibrated loose and out, so I wanted to just make it better than it was. It has been like this for 17 years, so it cant be too bad.
If I was to solid mount down the road, I would at least still shim the gap with rubber first.
I will definitely update this thread with any problems, if I have any. I am figuring the lock tight may not hold, then I will switch to studs and jam nuts.

[mkassab]

welded studs would be great.... but if your frame is powder coated then I wouldn't weld. I suggest you leave as is with to possitle exceptions. 1) add a jame nut to your bolt (a thin one) and tighten down on frame. and/or 2) do the "aircraft" thing... i.e., drill a small hole in your bolt within your spring area and add saftey wire to it.

[davids2toys]

I already purchased allen headed studs (I think they are called cap sockets) and jam nuts. These studs only came black oxide and grade 8. Only 98 cents a piece...lol

[Glenview289]

This link will lead to our build forum that shows modifications we did to our motor mounts. It is basically a 5/16" bolt that replaces the rivit that holds the mounting plates and rubber together in the motor mount. The Contemporary Cobra site recomends this on their cars. Their build site is an excellet resource for info as they also use Jag components. Lots of good tips! This mod will take about 50% of the movement out of the motor mount as it allows movement in compression only, while still giving the rubbers isolation properties to minimize engine vibrations.

http://www.uniquecobra.com/forums/showthread.php?t=6836

Bill

[davids2toys]

This link will lead to our build forum that shows modifications we did to our motor mounts. It is basically a 5/16" bolt that replaces the rivit that holds the mounting plates and rubber together in the motor mount. The Contemporary Cobra site recomends this on their cars. Their build site is an excellet resource for info as they also use Jag components. Lots of good tips! This mod will take about 50% of the movement out of the motor mount as it allows movement in compression only, while still giving the rubbers isolation properties to minimize engine vibrations.

http://www.uniquecobra.com/forums/showthread.php?t=6836

Bill

Very interesting, I will have to take a look at that. The Weavers or anyone else never mentioned this...Thanks!
Have not really looked at the motor mount except to feel it to determine if it was solid or not. Can this mod be done without removing the motor mount or lifting the engine.
That is a good link, makes me want to post the driveshaft loop we made...loop section removes with 2 pins(30 seconds), also incorporates the seat belt mounts to the bar section so now it is basically mounted to the frame instead of thru the fiberglass floor only. i never like that original set up, seemed like it would pull right thru the flooor in a good crash!

[davids2toys]

Just looked around for the contemporary site with no luck, could you provide a link?

[mkassab]

Very interesting, I will have to take a look at that. The Weavers or anyone else never mentioned this...Thanks!
Have not really looked at the motor mount except to feel it to determine if it was solid or not. Can this mod be done without removing the motor mount or lifting the engine.
That is a good link, makes me want to post the driveshaft loop we made...loop section removes with 2 pins(30 seconds), also incorporates the seat belt mounts to the bar section so now it is basically mounted to the frame instead of thru the fiberglass floor only. i never like that original set up, seemed like it would pull right thru the flooor in a good crash!

I'd like to see you "loop" set-up

[mkassab]

Just looked around for the contemporary site with no luck, could you provide a link?

I just Googled Contemporary Cobra.... nothing specific.... maybe club cobra?

[Glenview289]

Sorry, my mistake. It is ERA's site. Try this link.

http://www.erareplicas.com/427/sampman.pdf

I am not sure if the motor mount mod can be done with the mount in the car, but may be able to be done one side at time with a jack under the oil pan and hanging on the other mount. We have changed the mounting bolts this way. Remember this is endorsed by ERA, not Unique. Drag racers have used this modification and engine plates to limit engine movement for quite a while.

Bill

[davids2toys]

I'd like to see you "loop" set-up

Here ya go

[davids2toys]

Sorry, my mistake. It is ERA's site. Try this link.

http://www.erareplicas.com/427/sampman.pdf

I am not sure if the motor mount mod can be done with the mount in the car, but may be able to be done one side at time with a jack under the oil pan and hanging on the other mount. We have changed the mounting bolts this way. Remember this is endorsed by ERA, not Unique. Drag racers have used this modification and engine plates to limit engine movement for quite a while.

Bill

Don't see it in here either...check it out!