7 Port Heads

[ClassikFan]

My son has been reading about Mini engine conversions featuring 7 port cylinder heads and asked me to explain.

I am presuming that a standard Mini has 5 ports, 2 inlet & 3 exhaust, so the7 port one has 4 inlet?

Can any experts confirm or deny please?

[i_should_coco]

Wtf?

Old mini or new mini? Old ones have 2 valves/cyl. New ones will be 4 valves/cyl. Only Audi / VW / etc. use 3 inlet/2 exhaust configuration AFAIK.

[gjm]

Stuart - yes.

[ClassikFan]

Wtf?

Old mini or new mini? Old ones have 2 valves/cyl. New ones will be 4 valves/cyl. Only Audi / VW / etc. use 3 inlet/2 exhaust configuration AFAIK.

Not talking valves, ports are the thing old chap.

[ClassikFan]

Stuart - yes.

Thanks gjm

[i_should_coco]

Ah... gotcha. Yeah, I remember from messing around with old minis that they had siamesed ports for some cylinders (i.e. where the firing order meant they were a cycle apart, so didn't interfere). IIRC the inlets were, and also the exhaust between 2&3 (or maybe it was the other way round?) Having separate ports would be better, but cost more.

[gjm]

Having separate ports would be better, but cost more.

About £1600+VAT for a built 7-port head. Good power though - 100bhp from a 1275 is possible.

[bigdur]

Arden 7 port heads were the classic conversion, in reality a well worked 11 stud head is much more cost effective, there are people manufacturing 16v heads for A-series blocks these days.

[gjm]

I think there was a guy grafted the head from a BMW K100 motorbike onto an A-series block, too.

[diceman]

K100 head has been done a few times now and is a nice upgrade to get 16 valves :-)

The other benefit of the 7 port head is it turns it in to a cross-flow design whereby the inlet is one side of the head and the exhaust the other side (as opposed to all on the same side as per the original 5 port head).
Benefit 1 is that it is meant to encourage better swirl and mixing in the combustion chamber.
Benefit 2 is that you don't have a hot exhaust manifold stuck right next to your inlet manifold/carb.

Buy him the David Vizard A series book - lots of info there.

[Samantha]

B16a2 conversion. Even seen it done with TBs as well (although that requires bulk head modification to fit). Lots of fun (old Mini obviously)

[purplepleaser]

Well the 7 port has the advantages of using a normal manifold and other bits so make it cheaper than the 8 port heads. Been awhile since I looked in to this as I was going to do the engine in the 60's pickup thats in the garage. Another good way for good reliability is to use a superchareger from a new mini. CArelfull of the gearboxes though, stick a twin pin diff in and it might be okay.

[purplepleaser]

The best way is a bike engine in the back, supercar money for the price of a frame, engine and welding.

[ClassikFan]

K100 head has been done a few times now and is a nice upgrade to get 16 valves :-)

The other benefit of the 7 port head is it turns it in to a cross-flow design whereby the inlet is one side of the head and the exhaust the other side (as opposed to all on the same side as per the original 5 port head).
Benefit 1 is that it is meant to encourage better swirl and mixing in the combustion chamber.
Benefit 2 is that you don't have a hot exhaust manifold stuck right next to your inlet manifold/carb.

Buy him the David Vizard A series book - lots of info there.

Might just do that, thanks Diceman

[freefallrob]

Vizards books are great

I miss my old minis (cry). I always used the A series myself, didn't seem to be a mini without one!

[diceman]

A few friends have commented that the swap to mid engine buggers with the handling. Short wheel base, mid engined and no weight at the front makes it a "very fast rotating understeering whirly-gig" I think was the phrase. Comments were also made about sticking in lightweight engines at the front making the buggers understeer. A friend who used to race them indicated that you had to load up the front wheels under braking to get the front turned in on a std car - reducing the engine weight therefore didn't help.

I have no experience of driving these funny engined machines myself - main comments from a guy who ran an 8 port turbo a-series

I have had a few minis and loved tinkering with the a-series.