3.9 V8i intake manifold

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I have seen a few threads. Best - yes? Expensive and complex and non standard looking - yes?

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Best-absolutely
Expensive-I got mine for about $400.
Complex-well yes the retro fitting of teh 14CUX stuff needs quite a bit of fabbing.
But you may gain 5-10% at lower revs with the original manifold altered, but remember it was designed for racing (SD1 Vitesse) and will never give much low rev torque while the Thor can give 50% more at say 2000RPM.

[img=http://img714.imageshack.us/img714/7060/comparison3a.th.jpg]

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Originally Posted by BigJon

I have seen a few threads. Best - yes? Expensive and complex and non standard looking - yes?

I have a couple of standard manifolds to play with.

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I paid $90 for mine with an throttle cable thrown in, from toorak tractor.

BMW have already done the R&D for you with this manifold.

$90 is a great price. I would happily pay that much. I saw one go for $150 on fleabay recently.

TRS want $400, he reckons he usually gets $850...

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Originally Posted by BigJon

$90 is a great price. I would happily pay that much. I saw one go for $150 on fleabay recently.

TRS want $400, he reckons he usually gets $850...

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:eek: bloody hell, I'm going back to get another - there's a few buried out the back of his place under all the old disco junk.

with the amount of dead 4.0 and 4.6 engines they should be cheap as chips.

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Originally Posted by Hardchina

:eek: bloody hell, I'm going back to get another - there's a few buried out the back of his place under all the old disco junk.

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If you can get another one at that price I am definitely interested!

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Originally Posted by BigJon

If you can get another one at that price I am definitely interested!

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I'll see if i can find you one, - the one i got for $90 was bare, just the manifold and throttle body... no fuel rail, injectors, idle stepper etc.

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Originally Posted by Traco

Quite a few TVR owners have done this. They use the same 14CUX hotwire efi. There are TVR Rover V8 specialist kits around in the UK that contain a manifold spacer and different length trumpets.

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They use shorter and larger diameter trumpets which puts power further up the rev range, the opposite of what is needed for low down torque.

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Originally Posted by Hardchina

I'll see if i can find you one, - the one i got for $90 was bare, just the manifold and throttle body... no fuel rail, injectors, idle stepper etc.

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That is probably all I need. I would be fitting all the 14CUX stuff to it anyway. I already have Gen III fuel injectors (yellow ones).

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Originally Posted by LOVEMYRANGIE

They use shorter and larger diameter trumpets which puts power further up the rev range, the opposite of what is needed for low down torque.

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Hence my original question about lengthening the trumpets.

I did some rough calculations when I swapped mine.

The key issue is the distance from the valve to the throttle body.
You could probably achieve a similar effect to lengthening trumpets by simply cutting off the throttle bit and welding a 20CM spacer into it. I guess the packaging is the problem whatever you do, and I doubt whether you can add much to the trumpets ( without running into air restrictions with the top of the plenum). I thought about adding a Phenolic/nylon spacer between the lower manifiold and upper but AFAIR the distances between the trumpets on the base plate made it impossible for me to do without specialist tooling.

The 3.9 manifold is AFAIR about say 45cm valve to port, say 180 to the top of the trumpet and say 100 or so to the throttle blade.
Total say 325MM .End cylinders maybe 50 or so more.

The Thor is about 45 plus 750-800 say total 900 MM from a front LH cylinder . I just measured it roughly so that is pretty accurate.
Big difference.
Regards Philip A