21 replies to this topic

[Marlin]

I am in the process of a complete restoration of my mini and am looking for some advice for when I build my engine. I currently have a cooper S head that came with my engine. it needs a complete rebuild. It needs guides, intake valves and exhaust seats. I have had it checked and there are no cracks in the head. i am looking to build a fairly high performance road engine and am wondering if this head will give me the performance I am looking for.

What i have planned for the engine so far...
1275 bored 0.040" over
Kent 286 cam
duplex timing chain
Weber DCOE 45 carb
some sort of electronic ignition
I am thinking it will be supercharged also

Should I keep the valves the stock size?
Should I install oversize intake and exhaust valves?
What other performance work can I do to this head that would be worth while?

OR...is this head worth working with?

[mini13]

whats the casting no?

if its an aeg 163 I'd sugest flogging it and getting something more sutable.

[Marlin]

whats the casting no?

if its an aeg 163 I'd sugest flogging it and getting something more sutable.

I just went and had a look at it. The number cast on the top is 12G1316. It also has 108 and 18 F cast on the top. Any good?

[mini13]

Thats not an S head, ( unless they were fitted on S's in canada)

its the casting that was used to enable smog air pump injection, they are sought after as they can ported more,

[Marlin]

I was told it was a cooper s head when i bought it. Not really a surprise that it turns out its not. Is that a good head for a performance road engine. It had double valve springs that came on it.
If its a good option then what work should I do to it?

[mini13]

I think it is not a bad option, I think it is essentially the same as the S head performance wise, If the head is off check the valve diameters I think they will be approx 35mm for the inlet and 29mm for the exhaust.

I would not recomend doing any modifications yourself as the mini head is a bit of an odd head to modify,

you could have it modded, but I think it might be worth looking at selling it as they are desirable for full race heads as you can mod them in ways the normal heads cant, and then buy a fresh modded head.

can you post pics of the ports? i

[Marlin]

I think it is not a bad option, I think it is essentially the same as the S head performance wise, If the head is off check the valve diameters I think they will be approx 35mm for the inlet and 29mm for the exhaust.

I would not recomend doing any modifications yourself as the mini head is a bit of an odd head to modify,

you could have it modded, but I think it might be worth looking at selling it as they are desirable for full race heads as you can mod them in ways the normal heads cant, and then buy a fresh modded head.

can you post pics of the ports? i

35mm and 29mm sounds about right from when I measured them before.
I wouldn't be doing the mods myself. I know the owner of a good automotive machine shop. I would be having his shop do it.
I will go take a few pics and post in a couple minutes
selling this head and finding one that is already done may be possible but keep in mind Mini parts are not as plentiful here as they are in the UK. the other thing is if I have the work done I know exactly what has been done and that it has been done right. Not taking any ones word for it.

[Marlin]

Here are a few pictures

[mini13]

Ah!

ok, that head has already been modded quite a bit, it is one of the "smog" heads and has had the smog ports blocked up and then been ported.

I say use it as it is,

check the valve stems for wear and check their fit in the guides, also check that centre brass plug, it looks like it has sunk a bit, if it has it could cause head gasket issues.

If you want to supercharge you will need to look at how big the chambers are to see what compression ratio you will end up with and then get pistons to suit.

[Marlin]

The exhaust valves had 0.001" of taper. i was told they were ok. the intake valves have 0.002" of taper. I was told they will need to be replaced. Guides need to be replaced. I was also told that the exhaust seats need to be replaced but the intake seats are ok.

Is it worth installing bigger valves or are the stock valves big enough for anything I could do with my engine?
Is there any other performance work I can do to this head?

[mini13]

that sounds like a good assement,

I presume the exhaust seats need replacing so unleaded fuel can be used,

It could be worth going for bigger valves, I would look at going for a 31mm exhaust, although bigger intakes can be installed I would stay with the current one to reduce the chance of cracking, especially if you do supercharge it

[Marlin]

Yeah the exhaust seats are to be replaced for unleaded fuel.
Thats a bonus that its already ported. I will stick with the stock intake valve size and upgrade the exhaust valves to the 31mm as you suggested.

You seem to be quite competent with mini engines. Other than the things I mentioned in my first post is there anything you would suggest for my engine build?

[Marlin]

Would these valves be a good selection?

http://www.minispare...c/C-AEG544.aspx

http://www.minispare...c/C-AEG107.aspx

[Cooperman]

They should be ideal for your application.
However, as above, if you are going to go to forced induction you will need to set the compression ratio to a lower figure than you will be setting with normally aspirated.
You should measure to see what comp ratio the head will give with its new valves and skim if necessary to get the figure you want. Between 10.3:1 and 10.6:1 would be good for your engine specification.
If you go forced induction you would need lower compression pistons and, probably, increased size combustion chambers, but only measurement and calculation will determine what is needed.

[Marlin]

What sort of power can I expect to get out of it with what I have planned?