35 replies to this topic

[Wil_h]

Couple of photos below of my SC setup. Turbocharged with single TB and CF plenum.

The SC head is far superior to the other cast ones available for many reasons.

Not sure about the comment above about warping, there is no evidence that aluminim heads warp any more than steel ones.

The whole advantae of the 7-port head is the ease of fitting fuel injection. Fitting carbs just seems pointless.

[MJWarren]

just out of interest does anyone know what the cost to bhp ratio between fuel injection and webers?

[mini93]

Making up a plenum and having a throttle body kills the idea of 7 port x flow head unless your going turbo in my opinion.

I still dont agree... the idea of the 7 port is the non siameas ports for inlets... a well designed plenum will give you even pressure across the trumpets on the inside

such as pictured above, narrowing the plenum towards the further end increases the pressure and means you can get even flow... remember the engine will only draw in what it needs to if your flow is counted on entry to the plenum you will get even power across cylinders and neglagable drop in power compaired to poorly atomised fuel ala a carb set up

[MJWarren]

That is a fair comment, but i personally wouldnt know where to start designing an aftermarket plenum to optimise flow into all the cylinders, and i cant think of anyone else that does either.

A choke per cylinder be it a bike carb, weber, or throttle body i think is an easier option from which to get good results for the aftermarket tuner. fair comment?

For instance, i know its not mini but when vauxhall moved on from the redtop 16v to the more eco friendly engines aftermarket tuners had all sorts of problems getting throttle bodies or carbs to run smoothly at slow speeds. Vauxhall did it by the very cleverly designed plenum which is exactly what your saying. I can completely understand where your coming from but its not for me.

[mini93]

i think were agreeing now... for ease of getting the car running yes, carbs... throw them on and near on away you go.
but still in the idea, if you got the cash for the head... a little time spent on the net researching and away you go. Personaly i found information in an engineering book, its a fundermentals book so its not in huge depth but it gave me the idea anyway.. skimming the net you can find something for sure. make some stuff from fibreglass and you can make yourself a nice plenium...trial and error would probably be the way forward, certainly with the sizing, iv heard some rediculas sizes quoted which should give velve running lengths, plenum capacity and bell mouth info... course, would be useful here if i had finished uni and i had all CAD lectures and flow design capability... alas... im more likely to do a happy medium, something which can at very least not hinder the flow... or just save money for some AT thottle bodies... or just throw on a turbo so you dont stuggle for your VE like N/a engines

[summs116]

ive got the same head as med do and running 45s for over a year now and will say on tick over / low speed the fuelling is crap really but when on cam and higher rpm its fine,but im just getting injection set up for it now,jenveys with omex/emerald management just for easier start up and drive ability plus more torque and bhp with a larger camshaft,
its cheap to slap on pair carbs as no manifold needed
it all down to what you want the car for...