Stage 3 12G202?

Post by **winger300** » Tue Feb 03, 2004 5:32 pm

What is accounted for by the stage number?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 43122&rd=1

This appears to look in good condition, but the valves aren't enlarged from standard, so what makes for the stage 3 rating?

Would this head give any significant performance improvement, on par with a 12G295 or something?

Post by **Alec** » Tue Feb 03, 2004 6:23 pm

Hello Winger,
if that is a 12G202 then it has been radically reshaped. I would say that being a Cooper head it is not a 202. It is similar in shape to the 295. I would doubt that there would be a significant improvement on a standard 295, unless other alterations are made to make use of the (hopefully) increased flow from a properly worked head.
What engine were you planning to fit it to?

Alec

Post by **rayofleamington** » Tue Feb 03, 2004 6:44 pm

The Cooper 997 and the Minor 1098 had the 12G202 according to the info shown here:

http://drcwww.kub.nl/~bogaard/heads.htm

The Valve sizes are similar between the 202 and the 295 but based on his rough measurements it's not easy to tell if they are standard or a little bigger like the 295. However if the casting says 202 that is more than likely what it started as. The seller has good feedback so that's a good sign
If you want to comapre it to the standard 12G202 I can lend you one!
I would guess the ports are increased quite a lot and at stage 3 I think it should have a sleeve (or something similar) to line up the ports on the head with the ports on the manifold.

Cam will probably know - he is (was?) the Mini boyracer...

Post by **winger300** » Tue Feb 03, 2004 7:03 pm

I was planning to fit it to a 1098.

Would this head be a good purchase then? It looks pretty clean, worth £40-50 maybe?

I was planning on getting a HIF38 carb, alloy inlet, and standard mini exhaust manifold, keeping my old exhaust.

Post by **rayofleamington** » Tue Feb 03, 2004 7:08 pm

It might be worthwhile if it is better gas flowed than the standard 1098 head. You'd need to make sure.
Hovever if you get a 12G295, and convert it to lead free it should eventually pay for itself..
I now have an unleaded 12G940, but need to double check the valve clearances on the block (The 940 has much bigger valves). I've used one before on a 1098 and it was fabulous.

Post by **Cam** » Tue Feb 03, 2004 10:43 pm

Winger,

I would say that head should provide a good performance boost to your 1098 as long as your manifolds, carb, air filter and exhaust were also uprated.

The stage system can be awkward as it has changed over the years. there used to be 3 stages when I bought my race/rally head from MED race engines and I went for a stage 3. Now there are 5 stages and apparently my head is now full race spec!

I would say that it is stage 3 (or possible stage 2) by the new ratings as the valve sizes sound standard (29.37mm and 25.4mm) but it has been gasflowed (apparently) and I'm not sure if the chambers have been reshaped? If the 202 has a beak in the chamber then they have if not then they have not. If they have then it's not radical.
I can't check as my spare heads are in the garage and I am not!

It would be nice to see the inlet ports though............

Probably worth buying in any case.

Post by **Benjy** » Wed Feb 04, 2004 11:03 am

Received this from the seller:

My mate says it isn't a standard head. Its all been gas flowed properly by a mini specialist and the inlet & outlet ports have been smoothed.

Post by **Benjy** » Wed Feb 04, 2004 11:07 am

I know this has been asked before, but, does a 12G940 fit a standard 1098 block? This looks to have much bigger valves and would give a higher C.R. (more efficient?), so is it better than a 295?

Also, how much would it cost to get a reasonable one recon'd?

I'd like to get a little more oomph from my Traveller as I'm used to the pickup, which I think had a 4.55 diff, so went up hills better (there are plenty of hills round here) and now I'm normally carrying 3 people (well 2.5), not one or two!

Ben

Post by **Alec** » Wed Feb 04, 2004 11:30 am

Hello Ben,
My wife's 1098 Traveller has a 940 head and runs well. (It also has an 1 1\2" SU and a long centre branch manifold.) I relieved the block to prevent the exhaust valves clashing. It had a 295 head until that cracked, and all I could find in a hurry was a 940 (I was looking for an unleaded head) and I can't really tell if there is much gain with the 940.

Alec

Post by **winger300** » Wed Feb 04, 2004 1:29 pm

im not entirely clear as to where the valves foul the block, maybe someone could elaborate. Do you mean that the valve when open overlaps the cylinder bore?

If the block is needed to be cut, can this be done at home? or something for a machine shop? and can it be done with the block in the car?

Post by **Peetee** » Wed Feb 04, 2004 4:09 pm

im not entirely clear as to where the valves foul the block

The combustion chamber of the 12G940 cylinder head is wider than the bore of the 1098 engine. When the valves open their edges can strike the block. The block is relieved (cut away at two specific points for each cylinder) to prevent contact. This is a specialist job that entails removal and stripdown of the block and should only be entrusted to an engineer familiar with such work. It is a very popular modification with Mini racing where regulations for the under 1000cc class allow the use of the 12G940 head. On a highly tuned engine it has very definite benefits but because of the machining costs, non-DIY approach and milder road tuning I have my doubts over the usefullness of the application on a 1098 Minor. It would probably be more cost effective to source a 12G295 or 12G206 head and have it ported and leave the block alone. As I have mentioned before, a 948cc minor with 12G295, HIF38 carb and matching manifold can hit 60 in 18 seconds, A massive improvement over the standard 30 second wouldn't you agree?
A similarly modified 1098 would return as good an improvement all for about £150 - if you're lucky on ebay!

Post by **rayofleamington** » Wed Feb 04, 2004 7:56 pm

For the 940 it depends on the clearance between the valve an the block. If the clearance is bigger than the valve lift then it will work.
I have a very well used 12G940 head that runs fine on a 1098 without a pocketed block, however the valves seats may be slightly further back than normal spec.
I now also have an MG metro (unleaded) 12G940 head but the 2 heads are in different counties so I've got round to comparing them yet. I strongly suspect I'll need to pocket the block to use it, but that engine is about to be stripped down for new gaskets so it won't be a lot of extra hassle to have a bit of machining done at the same time.

Post by **winger300** » Wed Feb 04, 2004 8:45 pm

i understand now, So i suppose with a 12G940 and a high lift cam, its only going to make matters worse.

I steadily progressing through vizards tuning book at the moment, it seems like a ram-pipe is a pretty common thing he uses, but there aren't any sold on ebay. seems odd.

and one more question...

how much could i expect to pay for machining work? say for hardened valve seats, cylinder head skimming, crankshaft regrind?

Post by **rayofleamington** » Wed Feb 04, 2004 9:01 pm

say for hardened valve seats,

The going rate for head reconditioning is £100 to £180 exchange from various Minor centres. What you get does vary but most will include new valves, valve guides re-cut inlet seats and hardened exhaust valve seat inserts.
You might be able to get it better if you go direct to the engine machinists, and also have the minimum work done (eg not have the valve guides done if they seem ok), however the less work you have done, the more risk you take of having spent money and still having a #### head.

Skimming cost me £20 (on a block not a head, but should be similar), but ££ will depend where you go and what mood they're in.

Crank - if you are really luicky you'll find a ready machined crank and oversze bearings from an unfinished project. I got one for peanuts a few years ago. Phone around for quotes on the bearings as the engine machinists will just offer you what their stockist quotes to them - I got stung once doing that, so never again! Always check prices before stuff is specially ordered !!

Post by **Cam** » Thu Feb 05, 2004 9:30 am

I steadily progressing through vizards tuning book at the moment, it seems like a ram-pipe is a pretty common thing he uses, but there aren't any sold on ebay. seems odd.

Ram pipes are a good idea but they have to be fairly longish (or wideish) to work properly. Trouble is that most (if not all) air filters won't fit over them so they have to be used without a filter which is not a good idea as my mate did that once with his 1300 Allegro and got a tiny piece of grit into his engine which settled in the gap between a piston and cylinder and scored a groove in the cylinder wall which caused his engine to start belching oil out of the exhaust (I was following him at the time) and I had to stop because the front of my car was covered in oil and the wipers just smeared it across the screen! Needless to say, the engine was totalled. So I really would not recommend running without a filter!!!

Maybe that's why they are not so popular and you don't see many on eBay.

Post by **winger300** » Thu Feb 05, 2004 12:09 pm

i see.

Is there much difference between those K&N flat pancake type filters, and the cone ones? I had wondered if the cone type incorporated some kind of ram pipe in its design.

Post by **Peetee** » Thu Feb 05, 2004 1:04 pm

I have a K&N cone filter with a stub stack that bolts inside. This is a substitute for a ram pipe and is about 10mm deep. The inside face flares out by about 10mm in much the same way as a ram pipe.

Post by **Cam** » Thu Feb 05, 2004 1:25 pm

Is there much difference between those K&N flat pancake type filters, and the cone ones? I had wondered if the cone type incorporated some kind of ram pipe in its design.

In terms of flow and filtration they are about the same, but neither come with a ram-pipe or stub stack. But like Pete says you can get a stub stack instead of a ram pipe or just don't bother as the difference is not really noticable.

Post by **les** » Thu Feb 05, 2004 9:36 pm

I think you can run ram pipes with some k&n filter housings without spoiling the air flow.

Post by **Cam** » Thu Feb 05, 2004 9:47 pm

Yes but only small ram pipes and very large filters. The majority don't fit.