5 replies to this topic

[stuwhitfield]

I caught my exhaust (SS RC40) on a speed bump today, pulling off the back box.

The middle mount (http://www.minispare...id=38293&title=) has split in two and cannot be reused as the bolt is lost.

I tried to remove the two bolts holding it to the subfrme so that I could replace it and they both snapped the captive nuts!

Is this bracket required? If so how can I get to the (non) captive nuts to remove it? I dont think there is enough room for my grinder in there.

Assusming I do get it off somehow would it be okay to weld some bolts to the subby to bolt the bracket to?

[Cooperman]

You should be able to drill out the broken bolts and re-tap to 3/8" UNF (up from 5/16" UNF), then get a new mount and drill out the mounting holes to take 3/8" dia bolts.
You do really need that mounting.
You might be able to get the broken bolts out if they have not sheared off flush with the sub-frame web. If the trapped nuts themselves have sheared off and are spinning inside the sub-frame, you will need to cut a retangular hole in the sub-frame web to get the old nuts out, then make up a rectangular repair plate slightly larger than the hole you have made with new nuts welded to it and weld that plate into the sub-frame web.

[stuwhitfield]

thanks Cooperman,\i think the nuts have shered off flush inside as it feels like the whole lot is just spinning.

is there a way of bypassing this original mount and using the hanger style fittings mounted elsewhere?

I think to get the grinder and welder in to do that amount of work would require the subframe to come out, and I cant really afford to have the car off the road for that amount of time...

[Cooperman]

If you could get the car really high off the ground, or better still on a ramp, you would be able to get the grinder in without removing the sub-frame.
All you really need to do is to grind off flush and make up a nut plate with 2 nuts the correct spacing for the 'choc-block' mount. Then you drill out the broken nuts to give a big hole, big enough for the new nuts on your nut plate to sit inside the sub-frame web and weld the nut plate in place. If you live close enought o me, near St. Ives in Cambs, I would be happy to do it for you as it's really quite straightforward if you have a grinder and a MIG welder plus a big trolley jack and some tall axle stands.
I'm afraid any other way of doing it is a 'bodge' and you won't have a secure system.
A tip, if I may. With the RC40 back box the box has a square end. On my rally cars I weld a skid/deflection plate from the front edge of the box forward to the pipe using 18 swg sheet steel. Then the exhaust box tends to ride over any bumps or obstructions. I also weld the entire exhaust pipe from the end of the manifold to the final exit to be a one-piece system. That makes it very strong. In addition I wire the system in place with old bits of wire coat hanger (I knew they had a life after the dry cleaners!) and use 4 rear 'cotton-reel' mountings with a support strap under the pipe at the very back.

[stuwhitfield]

Thanks for the offer but I'm afraid I'm miles from you (Hastings - TN34 3BA). I've got some ramps, trolly jack and stands so with that lot I should be able to get it higher than I managed the other night. I guess the towbar will need to come off aswell,

The deflection plate sounds like a great idea. Im not sure I understand your extra coat hanger bit though!

[Cooperman]

I get an old wire coat hanger and wind a length of it around the underneath of the pipe and over the bracket, then twist it until it's almost tight. This is just a bit of extra support for a rally car as if the exhaust comes of you have to retire from the event. I do the same at the back (centre exit exhaust) with the wire going under the pipe and over the sub-frame cross member. Never lost a system on an event yet.

Edited by Cooperman, 20 May 2010 - 01:41 PM.