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VHPD throttle boddies

Flying kiwi

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You will need to fettle the inlet port entry to match the huge and misshapen runners. If they are the early type with the swan necked seperate manifold then the runner line is too low and both the bottom and top of the port entry will need substantial enlarging to avoid a step. The later ones may have a better port line, I haven't seen the manifold flange configuration, but the hole will be 3-4mm too large so the ports will need opening up to match. Invariably it makes a bit of a dogs breakfast of the inlet port and ideally you should remove the head and strip it to do the work.


You may get away with packing the ports with wadding and grease and doing the matching on the car but... it wiont be ideal.


You shouldnt need to port the head unless you want to.


You will need an after market ECU.



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There is a hint in what Oily is saying that you get the best bang per buck by taking a balanced view across the whole system.


Changing to throttle bodies necessitates port matching

Changing to throttle bodies needs a mappable ECU and a mapping session

Port matching is easiest done with the head off

The early VHPD throttle bodies have a restrictive manifold - which ones are you planning to use?


So changing to early VHPD throttle bodies sucks you into a significant spend for a compromised solution that doesn't actually give you much more than 10bhp. The problem of not looking at the whole solution. You have asked a follow up question that asks: "What about changing the cams while I am at it?" There are many answers to that, depending on your aims.


Rather than taking a piecemeal view, can you specify a target power output or a target budget and get much more specific answers. It sounds like you have fixed on the VHPD throttle bodies, but which ones? Have you got yourself a good secondhand deal? There are many other solutions that you have ruled out directly by that choice.

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In answer to some of the questios.


1.The THB`s are off a 2000 VHPD [not yet sure if they will be cheap as he is my brother-in-law].


2.As for the cams, the question was really to give me an idea as to how this will improve performance. Initially i was going to fit the THB`s on the existing head which will be ported to suit, as well as this i will be fitting a new exhaust system [sLR].


3.A new ecu will of course be required, so a mapping session will be needed.


4.Then look at fitting new cams.





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The head can usefully be ported, preferably to bigger valves (29.5mm/26mm), it doesnt make sense not to do the cams at the same time, the Piper BP285H cams would be ideal for this setup, they require Pipers springs but will work with the standard hydraulic followers, These will peak at around 7500 and with a big valve ported head and the TBs can give 180BHPish. A step milder would be the Piper 633 profiles.


There is a alibrary of maps available for the Emerald M3DK, including at least two that will be similar to your proposed configuration.



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