About 7-Port Heads...
Turbo Mini Forums

Dear Fellows,


I decided to open this discussion to debate about what to chose and why to chose, when we are thinking to go for 7 port heads...

I actually have a 7 port from Minisport, full race head 38/31 stainless steel valves, top springs, drilled to 45mm , very expensive in that time and a few years latter the alloy ones started to be comercialized with a better quality and competitive price actually, but until that point?

So i'm considering some points to favor and some against...
For example the steel AKM head could have more favor points that could translate a better power gain:

-Better resistence, less deformation at overheat.
-Better flow due the porting 45mm Stronger intakes, seems the other ones are only comercialized in 40mm possible because of the risk of cracks.
-Bigger valves, possible due a very strong chamber hall.
-Overall better power gain.

Against:

-Heavy Material
-Less temperature dissipation
-Handcrafted Ports / chambers
-Need to be drilled if you want to go for Dry Deck


MED Head...
Favor Points:

-Better heat Dissipation
-Dry Deck option.
-Good Flow 40mm
-Lightweight

Against:

-High Cost
-Handcrafted Ports/chambers
-More deformation with overheat (Valves/Valve Guides, Intake Manifolds)


SC Billet Head
Favor Points:

-Better Quality/Cost
-Good Resistence/deformation
-Top Machined Chambers and Intakes CNC
-Lightweight


Against:

-DCOE Manifolds not included
-Small Intake Valves
-Probably less power due Valve dia.


There are some tips, please fell free to discusse them... and to intervene.

Please leave us your opinion about carburation for this heads, discusse them would be great, because they are like blood to the heart.


I hope to bring some interest for you...
Cheers,
Diogo Lima

Edited by Diogo Lima on 28th Sep, 2010.

diogo ,what rev range will you be using ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Due to cost considerations, I went for a Pierce (MED) head with twin 40mm Dellorto DHLAs. The standard valves will do for now, with the option to up them later.

I've also bought a Turbo Phil dry deck kit, will let you know how it works out.

I have the SW23-07SP With a range between 3000rpm and 8500rpm, the engine will have 1460cc capacity and i was thinking to use 11.7CR for 100octo BP comercial fuel, i thing i could go more CR but i will consider the using of N2O later, the car would be mainly intended to hillclimb and circuit.

Diogo

Edited by Diogo Lima on 28th Sep, 2010.

Hey Diogo...I would say that if you have the AKM already, go with it. 45mm intakes are definitely large on an A series engine of any size, but if you are going for full on WOT most of the time in a higher rev range, then you should be fine.

Also, you may want to go with a traditional grind on your cam as the scatter pattern was designed mainly to work with the odd properties of the 5 port siamese head that is eliminated with the 7 port that has no shared intakes. I currently use a kent 276 on mine and would consider 1 or 2 steps up for sure on a race engine.

Not sure on the AKM head how much space they left for skimming to get CR up, but I talked to Mike Pierce about his 2nd generation head with the 8mm plugs....this was designed specifically for clearance to skim....he told me that he has some independent developers running at 15:1 for testing purposes.

I'm very happy with the quality of the Pierce/MED hillclimb head, but to do over, I would probably look into SC's setup that is designed to take injectors straight away.

Eric
my pics.... http://www.fototime.com/inv/7AAF37CF3EFA956

I agree about dropping the scatter pattern cam. Not relevant with the crossflow 7 port. Keep it simple....(and cheaper too).

Very thanks,


About CR i could easy go for 12.5 with comercial fuel, i will not risk more, because we have about 38ºC in the early summer and i'm afraid of detonation.

I allready have the camshaft, and the Weber 45 DCOE carburators to, like you said when i buy them i was thinking in hp at high revs, but i buy the 152G with extra progression holes for compensate the combustion at lower reving i think i will get a good tune with that, i'm expecting about 165/170hp from my build.

About ingnition i have the Aldon 100AR, but i'm consider going for ECU, i will probably choose the SC typhoon to let me the oportunity to evolute for DCOE Throttle Body (EFI) there i will probably go for 40mm.

I will choose electrical cooling system to get less hp drain...


Diogo

Ok,

from what I have seen/heard I'll work through the DCOE type 7 ports in chronalogical order...

AKM,

45mm intakes with big ports, works ok but the gas speed suffers due to the big ports so only comes into its own on big lumps and screamers, you need to be looking at 1380's with at least 300deg cams and high compressions and going to 8500rpm+ difficult to get the torque of a 5 porter due to the low gas speed.

Minisport,

essentially the same casting as the AKM, but with 40mm intakes, still suited to race lumps more but not as much so as the AKM, should be good with cams or 280-290 odd deg upwards.

Peirce 7 port.
porting wise very similar to the minispares 7 port from what I have seen, but with 33mm valves as std rather than the 35 of its minisport and AKM predicessors, a bit shit really as the smaller valve is just making the ports looks smaller and screwing up the gas speed, first think to do is stick in larger valves!! some improvements to the waterways, but there have been some issues with core shift. the alluminium I belive is a step forward, easier to repair, better heat conduction, lighter.

HRE head,
as per the peirece head but has larger intake valves and has been worked on.


Essentially with any of the above 7 ports forget about trying to "flow" the intakes, you need to get the valve an throat area flowing as efficiently as possible to get the gas speed up to in turn pull up the bottom end torque.


SC head
First of its billet so there will be no probs with core shift that is seen in the other heads, the ports are a much better size to start with, and it has injector holes provided. you will be able to use this head to make a docile street lump if you wish, but you also have the option to remove material that just isn't there with the other heads.

fueling wise, injection is the way to go, unless you really have to stay with carbs.