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Discussion Starter · #1 ·
Initially I just put this down to less sound insulation on the GT but it's soooo loud that it must be a symptom of something else.

The car is a standard IX GT, with standard exhaust, but the engine has Manley and Weisico forged rods and pistons. The resonance is loud enough to drown out the radio and to warrant ear plugs. It occurs between 3800 rpm and 4800 rpm. Above 5k rpm and it's relatively quiet once again.

I'm wondering if it could be any of the following:

1. different engine mounting bushes used following engine rebuild?
2. lack of sound deadening on the bulkhead?
3. engine misaligned following rebuild providing conduction path for resonance.

Has anyone heard of this before?

Cheers
Calum
 

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I had poly engine mounts fitted & got bad resonance at around 5-5.5k particuarly in 4th & 5th, replaced them with standard bushes & all back to normal :rolleyes:
 

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Mine is built the same way, but i have no resonance problems even after 21k, i´d go back to standard mounts.

Who built it for you?

;)

Al
 

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Discussion Starter · #4 ·
I bought the car already built so don't know who did the rebuild. So far it sounds good to me that other folk don't have the problem, so it must be fixable :)

It's very hard to live with that's for sure!
 
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Sounds like one of Nigel's cars with that spec.
I would get your exhaust checked for clearence on the sump and transfer box first. Did you buy it second hand? Nigel doesnt normally fit Polyurethane engine mounts?
 

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I guess this is Colins old car (Rossocorsa) ? He was always real helpful when I looked at buying it so maybe if you PM / phone him he could put you in touch with someone who could shed some light ?
 

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Discussion Starter · #7 ·
Yup, it is indeed Colin's car supplied by Nigel. Nigel has just been in touch (thanks Nigel) and I'm happy that it's nothing to do with the forged build. I have the build photos and the work was done with the engine in situ and the bushes were not replaced with poly.

Thinking back, Colin did fit a Greddy ti system and then refit the original exhaust so it's perhaps as a result of a clearance issue during the refit that I now have the resonance. Colin was always meticulous with his car and I bought it when he was still running it in at under 4k rpm so Colin would not have experienced the resonance. I'm about to replace the exhaust anyway, so it should just happily cure itself :)

I'll update with the good news once it's resolved.

Thanks to all ... I've been rubbing my chin over this one for a while now.

Cheers
Calum :)
 

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Has the balance shaft been aligned properly? It does 2 turns for every one of the crank and if misaligned it will give you exactly the symptoms described..

Phil
 

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My car has the same internals and is very smooth and quiet.

I would suspect the downpipe or system vibrating or touching somewhere ie sump/crossmember or even the rear valance.
 

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Calum, firstly I would check exhaust for fouling/security,then bolt check on engine/gearbox mountings etc.I know it's a bit of a trek for you but I would be more than happy to check it out for you ;) .

Colin.
 

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Discussion Starter · #13 ·
Colin,

great of you to pick up on this thread.

I'm actually down in Broxburn quite regularly so if you're happy to, I'll perhaps take you up on your offer. I'm about to fit the Magnex downpipe and Miltek decat you gave me, along with a cat-back (yet to be decided upon) so I should really do that first and then if it suits, I could drop the car off with you for a weekend if the resonance persists.

Cheers :thumbup:
Calum
 
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