23 replies to this topic

[The Principal]

Hi all, anyone have any experience of 7 port heads? which is better iron or alloy also can you easily cut bigger valve seats in the alloy heads?

 

 

Minisport iron - http://www.minisport...ides-seats.html

 

Webcon Alloy - http://www.webcon.co...opexd.asp?id=36

 

 

ta

 

[Tommyboy12]

Define better?

 

The iron head has the possibiity to be more durable because iron is fairly forgiving as an engine material. It will expand and contract at the same rate as the block so you are also less likely to blow headgaskets. You also arent mixing metals in the cooling system which can cause issues. The alloy head is cheaper of course but that doesnt make it worse.

 

You need to consider the stock flow characteristics of the head really as to whether the price difference is actually worth it. Otherwise you will be paying extra to get the head flowed. Cutting bigger valve seats into heads isnt material dependent though, you could do it to either head.

 

If money was no object I would personally go for the iron head because of continuity with the cooling system and the expansion and contraction.

 

Also there was an article on all these heads in the last Mini World. Might be worth checking out.

[Vipernoir]

Just to confuse you more, I'd use one of these:  http://www.twinkam.c...&aid=SC216.001

[diogoteix]

Alloy heads have better heat dissipation, solving the classical issue of hot-spots of A-series engines.

As a result, the are also supposed to be less inclined to "knock", allowing slightly higher compressions.

 

As for bimetallic corrosion between a cast iron bottom end and an aluminum alloy head, it should be very very limited for 2 reasons:

- cast iron and aluminum alloys are quite similar in terms of electric potential and are both on the "negative" side

- the cooling liquid is supposed to be a very poor electrolyte

 

Bimetallic corrosion should be much worse between cast iron and titanium, copper or bronze and we can see these metals in many engines parts, including copper gaskets, in direct contact with cast iron surfaces.

You can have a look at page 3 of the following document to see a scale of electric potential of various metals:

http://www.npl.co.uk...71105114556.pdf

 

I'm precisely in the process of choosing a 7 port head. I'm inclined to take a MED 7 Port Trackday head. it costs 1725GBP inc VAT, is made from the same base as Webcon's, but is fully ported by MED and fitted with decent valves (37/31 instead of 33/29) and springs.

Specialist Components head was another option seriously considered, is very close in price (1650 inc VAT) but needs specific throttle bodies (36mm with a bespoke spacing and no injector plug, since injectors are directly plugged into the head) bringing the total cost higher (300gbp more for a SC "kit" excluding ECU).

 

Cheers

Diogo

[Orange-Phantom]

I've got an original AKM 7 port head which is the same as the Minisport.  In it I've got 36mm inlet valves . 31mm exhaust valves, 1.5 Roller Rockers, Custom JE forged pistons with 10cc offset dish which gives a compression ratio of 10.5:1, running a Swiftune SW-10 Cam with a pair of DCOE 38's doing the fueling!  With that spec I'm getting 150bhp at full chat.

 

All I can say is I find it brilliant and great fun to drive (not that I'm biased in any way when it comes to mini's)!

 

With the Minisport head you can go for carbs (2x DCOE 40's) or injection so there is some flexibility there.  It also fit's nicely under the bonnet (just) and I'm also running a custom ITG air filter on it too!   I can't comment on the other heads and which one is better.  I suppose each head will have it's advantages and disadvantages in some way.

 

Regarding corrosion and hot spots I also use Millers Extra cool which has a powerful corrosion inhibitor and increases laminar flow of water thus help reduce the formation of any hot spots.  It's only £10 a bottle so well worth it IMHO prevention being better than cure and all that http://www.millersoi...ctor=Motorsport

 

Re MED my brother has used their services many times and he has always been very happy with them.

[The Principal]

Thanks all for replying, anyone used a webcon head? if so how well does it flow and have you enlarged the valve seats?

[DILLIGAF]

Alloy has a higher resistance to detonation than iron, so in theory you should be able to run higher compression.......

[tiger99]

True, because of its higher thermal conductivity. Copper would be even better in that regard, but I don't think its other properties make it usable, unfortunately. And, silver is 3% better than copper....

 

But ali has a limited fatigue life compared to iron. Ok, in a modern engine the head will do maybe 300k miles without failure, but that is a head from a mainstream manufacturer, with lots of development budget, and usually on an engine in a fairly mild state of tune. An aftermarket ali head from a small manufacturer can not have had as much development, simply due to the cost of testing large numbers for high mileage, so it may well turn out to have a short life. But perhaps it will be ok, if you find one that people have successfully run for high mileage it should be ok.

 

All I am saying, is ask around before spending serious money on an alloy head. Pick one that has proved itself. Or, take the safer option of the iron head.

[diogoteix]

Thanks all for replying, anyone used a webcon head? if so how well does it flow and have you enlarged the valve seats?

Webcon, MED, and some others (on Ebay for example), are all base on the same casting from Pierce Manifolds (from the US). I've read in many places that this base casting, presented bare or with 33/29 valves and standard springs, really needs some work if you want to get a better performance (at least maximum HP) than a nicely tuned 5 port head. It's exactly what MED does, with its "trackday" and "race" 7 port heads.

Minispares went the "8 port way", with a specific casting, but I just don't know why other performance part providers, like Minispeed or even Calverst.com, don't give it a try? They probably could offer a slightly better price point than MED. The option always exists, off course, to buy the bare casting and have it tuned at home (but you really need quite a lot of specific hardware to do it properly) or by a professional with a better set of valves and springs.

[[email protected]]

SC head looks awesome! 

[diogoteix]

Yes SC head is a fantastic piece of alloy! And performance-wise is seems able to offer the best results, but to be sure it would be great if Mini Mag could do a "side by side comparison".

The only drawback is the price, not of the head, but of its specific throttle bodies...

[DILLIGAF]

Yes SC head is a fantastic piece of alloy! And performance-wise is seems able to offer the best results, but to be sure it would be great if Mini Mag could do a "side by side comparison".

 

The comics are more bothered about upsetting there advertisers now a days, can you imagine a test between something all the major players produce.......

 

Everyone would buy the best product, which would be good for us. But the producers of the crap ones would stop there adverts in the comic......

 

Which at the end of the day would effect the comics profit, because all the major money they make comes from the adverts.......

 

This is why there all basically just catalogues, not real informative independent magazines anymore......

Edited by DILLIGAF, 22 August 2013 - 09:48 AM.

[Frisco]

Still nice to get your car featured though

[Orange-Phantom]

Yes it would be great to have side by side comparisons of various equipment so that people can make proper informative decisions based on fact rather than suppositions.

 

But as has been said unfortunately money gets in the way, such is life.  Doesn't mean it's right though!

[mini13]

the SC head is better due to the ports being the right kind of size for the valves so you get a much more uniform gas speed through the head.

 

Given the choice I would choose an alloy head over an iron one as repairs are much easier and cast iron is more prone to cracking.