The V8 Owners Forum -

Thought I would just throw this open to disscussion and see what responses I get.
Have a 1998 4.6 Rover which is going into a 3500 VDP. Fast road cam ( still to be bought)9.75 comp,ported late 4 bolt heads,tri-y pipes,lumenition ecu for fuel and ignition.I have a fair collection of intakes to choose from but need to make a final decision on which to use.
Have a choice of early federal,3.5 RR flapper,3.9 RR hotwire,4.6 GEMS and 4.6 Thor/Motronic.I was leaning towards the Thor however looking at the GEMS it appears to have a larger plenum than the 3.5/3.9 twins.I havent stripped it down yet so am not sure about the trumpets.Looks a little higher over-all than the other 4 too which might hit the bonnet too.
Any thoughts appreciated.
Doug

in that car I would for for either the gems or the hotwire. So far as I know they are much the same. The thor in theory would give you a bit more bottom end at the expense of top end but it does look good. Flapper is harder to get injectors for so no point using it when you have the others and the federal is the most restricted of all the inlets probably including SU's.

Yeah from a looks point of veiw the GEMS wins hands down,I guess my concerns with it are airflow related i.e the throttle body bore is 64mm the same as a 3.5L as oppossed to the Thor at over 70mm.I guess I will have to pull it apart and measure the trumpets but suspect they may be the same as a 3.5L too.
Doug

what is it you have planned for the engine as the standard hotwire setup is good for 300bhp with injector changes.

good for 300BHP

Really? What kind of work would you need

change lots of stuff underneath the injection system

(So I had assumed!)

katanaman wrote:change lots of stuff underneath the injection system

don't i know it

The motor is mostly for fast road use,odd track day and use as a tow car thrown in just to muddle things up too.I using a Lumenition c460 for fuel and ignition.Apart from the manifold collection I dont have a lot of factory hardware for Gems ,Motronic or hotwire setups.3 running flappers though.
The thor manifold has pretty much everything from the manifold base up (idle control,injectors/rail ect)the Gems 4.6 is much the same(cut out motor inc regulator green band injectors/rail knock sensors ect) hotwire just manifold,trumpet base ,plenum and fuel rail,and more federal flappers than I know what to do with.
From the info I have ,the greenband injectors are high impedence (which I need )and flow more than the slim green Thor ones.However the Thor has a much larger throttle body and fuel rail which might be handy if I get bored with the aspirated motor and whack on the m90 eaton thats gathering dust in the shed.
Doug

From what you say I think the hotwire/gems style will do you fine. Even if you use the charger the restriction isn't so important. I am guessing that although the Thor might have the bigger valve its the most restrictive internally as it was designed for high torque low down. It could also be that its runners are tuned longer but either way it doesn't sound like that's what your after. The older hump style plenum is more tunable too via longer, shorter larger trumpets. The Thor would take a huge amount of work and special tools to do anything with and that's probably still limited to porting it out. By the way according to another thread below this the 3.9 injectors flow the most out of them all.