Siamesed Plenums

adamnreeves · Post by **adamnreeves** » Thu Mar 08, 2007 4:11 pm

I know I have probably spelt it wrong but you know what I mean..hopefully. Anyway, whats peopls opinion on these, worth getting. I need to get my plenum chamber for my build.

Post by **katanaman** » Thu Mar 08, 2007 5:21 pm

Depends what your doing, if your approaching the high 200's or beyond power wise then yes. Its isn't going to do much on its own though so you have to take care of the actual inlet and port that too. You also need an ECU that can cope with it as in it uses MAP or at a push TPS. The standard system is good for about 300 bhp.

adamnreeves · Post by **adamnreeves** » Thu Mar 08, 2007 8:59 pm

I have stage III heads and inlet manifold and plenum base to match. Capacity is 4.6. I have a Piper 285 cam installed. Bleed down lifters. Going to be using megasquirt and megajolt. I would hope that I am approaching 300BHP so sounds like I might as well for for Siamese Plenum chamber.

I've yet to get my fuel injectors, any recommendations? I think the standard ones wold be insuffient?

katanaman wrote:Depends what your doing, if your approaching the high 200's or beyond power wise then yes. Its isn't going to do much on its own though so you have to take care of the actual inlet and port that too. You also need an ECU that can cope with it as in it uses MAP or at a push TPS. The standard system is good for about 300 bhp.

Post by **katanaman** » Thu Mar 08, 2007 9:07 pm

Yes if your approaching 300 bhp you would be better to get larger injectors to be safe. Personally I think your being a bit optimistic of that figure with a 285 cam but who knows.

softdash3.9 · Post by **softdash3.9** » Thu Mar 08, 2007 9:08 pm

One on fleabay now, looks nicely made, search on twin plenum

Post by **katanaman** » Thu Mar 08, 2007 9:19 pm

I think that's Philips from this forum (daxtojeiro)

Post by **Coops** » Thu Mar 08, 2007 10:08 pm

im also watching that plenum

ihatesissycars · Post by **ihatesissycars** » Thu Mar 08, 2007 10:31 pm

Thats not Phils, just one like it.

adamnreeves · Post by **adamnreeves** » Thu Mar 08, 2007 11:40 pm

The cam is the 285i which adds extra 35bhp. stanndard 4.6 is 225 so that takes it to 260. I have stage III heads gas flowed with big valves and I am going to have custom headers. If I do not get to 280BHP I will be bitterly disappointed and I will throw all my toys out of the pram! Plus I regularily see people quoting figures of 300BHP for 4.2s.

katanaman wrote:Yes if your approaching 300 bhp you would be better to get larger injectors to be safe. Personally I think your being a bit optimistic of that figure with a 285 cam but who knows.

adamnreeves · Post by **adamnreeves** » Thu Mar 08, 2007 11:42 pm

Please don't nick the plenums! I have been trying to buy some for about 3 weeks.

pitsnow · Post by **pitsnow** » Fri Mar 09, 2007 6:46 am

Are you sure you will get this under the bonnet of the Westfield?
It would not on a Rush.

Wotland · Post by **Wotland** » Fri Mar 09, 2007 9:06 am

AH AH we are here several to follow this ebay auction. Me too for my twin supercharger project.

Post by **katanaman** » Fri Mar 09, 2007 9:14 am

adamnreeves wrote:Please don't nick the plenums! I have been trying to buy some for about 3 weeks.

You really think something like that would stay quiet on this forum

adamnreeves · Post by **adamnreeves** » Fri Mar 09, 2007 10:02 am

Nope, but my trumpets are already lowered and half expecting to have to cut down the plenum also but I shall leave that until the engine is in the car and I can see how much I need to remove.

pitsnow wrote:Are you sure you will get this under the bonnet of the Westfield?
It would not on a Rush.

chodjinn · Post by **chodjinn** » Fri Mar 09, 2007 10:53 am

Have you lowered the actual trumpet base itself? Think you can get about 9mm off there, plus whatever off the plenum makes about 25mm loss IIRC. Will check my MGB book when I get home