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MG MGB GT V8 Factory Originals Technical - Putting the Trumpets back in

I've had the trumpet tray from my Rover Hot-Wire fuel injection shaved down by 16mm to get the kit under the bonnet (hood), and I'm ready to re-install the trumpets. They came out pretty easily once I'd heated the thing up in the kitchen oven at 210 celcius.

What I'm not clear about is whether I should be using any kind of compound around the trumpets when I re-install them, or whether they are simply held in by the alloy cooling and contracting around them. Looking at the casting there does seem to have been some sort of material around the trumpets, unless it's just burnt fuel residue.

What have others done?

Mike
Mike Howlett

A smear of Loctite. I can't remember which number I used, but your local parts shop should be able to advise. Barrie E
Barrie Egerton

Mike,

The trumpets would most likely be held securely enough by the cooling of the alloy around them but a bead of sealant will ensure an airtight seal as well as some extra insurance.

A pinhole air leak between the two will be a lot of work and time to track down and remedy.

Pete.
Peter Thomas

I used some silcone I had. "Ultra grey" solvent temperature resistant stuff.
Don't forget to shorten the two pairs of end trumpets.
Also if you shorten all 8 of the trumpets a little bit more than necessary you get better air flow and a little more go. Oddly, although shortening the air trumpets is supposed to increase horse power at the expense of "low end torque", I felt I had more accelleration from stationary. Perhaps it has to do with the lightened fly wheel (half an inch off a range rover one) or perhaps the car is so relativly light I don't notice any less low end.
Either way, its better. In my case it chanced to be around 8mm (because of me getting another tray machined and keeping the old trumpets). So 8mm may not be optimal.
Peter Sherman

Thanks fellas. Yes I've remembered to shorten the outer four trumpets by 7 mm to restore the difference in height. I think I'll leave them alone otherwise. The car will already be much quicker than anything I've ever owned in 40 years of driving.
Mike Howlett

Well, the trumpets are back in place. I found some high temperature RTV silicon stuff by Loctite and used that. I must say removing them and refitting them was nothing like as difficult as I thought it would be. With the oven at 210 celcius, the trumpets become quite loose. The only problem was the fumes and smell inside our oven. I should have cleaned the assembly better before I began!
Mike
Mike Howlett

Mike,
Good to hear you had success with the trumpets.

Try using some of that activated carbon stuff sold for deodourising fridges to get rid of the nasty smells in the oven.

I have used it with positive results after using the oven to bake wrinkle paint.

Cheers , Pete.
Peter Thomas

This thread was discussed between 30/09/2007 and 04/10/2007

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