12G940 Cylinder Heads

[jaguar68]

Hi Guys,

Would the smaller valved version of the 12G940 head make much of a difference over a 12G295 head when fitted to a 1098cc engine?

Also, would fitting a HIF 38 with a K&N type air filter and a LCB exhaust make much of a difference when using the smaller valve 940 head?

Regards

John

[TomLS]

From my research, the 12G940 head is the best for the 1098cc engine, as the 295 head gives more power at high revs - which the 1098 doesn't like!
I've just bought a HS4 carb and manifold, and a 12G940 head along with a metro camshaft for my 1098. The only remaining decision is whether to port the head .

[linearaudio]

From my research, the 12G940 head is the best for the 1098cc engine, as the 295 head gives more power at high revs - which the 1098 doesn't like!
I've just bought a HS4 carb and manifold, and a 12G940 head along with a metro camshaft for my 1098. The only remaining decision is whether to port the head .

The Metro camshaft won't gain you anything, unless it is the MG Metro version!
Just dumping a standard 940 head on a 1098 will give 8-10bhp, anything else you do to the head will not create a similar jump in power, but if you have the inclination and tools,it can be improved, particularly by paying the exhaust ports some attention, just like I didn't The throat is quite restricted around the valve guide boss area, and the sharp turn for the exhaust gases can be usefully improved! On the inlet side, for a standard 1098, just a light cleaning up is probably all that is worth doing!

John, anything other than the standard exhaust will only help the efficiency of the engine. An HIF38 is a good carb with a AAA needle. K&N will breathe well, but may be a bit noisy, if that worries you! The MG Metro air cleaner is a good compromise, being quite good flowing (up to the speeds the 1098 works best at), and very quiet.

[bmcecosse]

The 940 small valve head is IDEAL for a 1098, and far far far better than the 295 head. I assume you are aware of the precautions to be taken. And yes - only the MG Metro cam is worth having - the Metro cam is virtually the same as the 1098 standard cam - in timing and lift terms - it runs a few degrees advanced, and does have the wider lobes of course.

[IslipMinor]

An HIF38 is a good carb with a AAA needle. K&N will breathe well, but may be a bit noisy, if that worries you! The MG Metro air cleaner is a good compromise, being quite good flowing (up to the speeds the 1098 works best at), and very quiet.

I have both air cleaner set-ups for the HIF6 on our 1380. The MG Metro air cleaner box, without the vacuum gubbins and with K & N filter inside is very quiet, whereas a large circular K & N is noisy, particularly at around 3,000 rpm, when there is a real intake 'bark' - without exageration it sounds like the big ends are completely shot! And of course 3,000 is used much of the time for normal motoring.

So why not just use the MG Metro air box? Because on a back-to-back rolling road session it cost 8 bhp! Vizard said that it was good up to ~100bhp, which is borne out on the RR, 104bhp with Metro, 112 without.

[chrisryder]

i have a K&N on my minor. I quite like the bark

[linearaudio]

all comes down to whether you want a noisy intake or not, then! Using mine as a daily hack, I want it as quiet as possible for my sanity's sake
As Islipminor says: Up to 80-90bhp the MG Metro box works fine, and better still if you get rid of the snorkel and thermostat bit.
If you can justify £40 for a K&N filter element rather than the standard £4 Coopers one then so much the better!

[MarkyB]

I agree, a noisy inlet or exhaust get old quite fast if you use the car a lot or for a long journey.

[chrisryder]

well yeah, i can't usually hear the intake noise over the exhaust. it's only when you put your foot down you hear a snort

[Bazzalucas]

Eh? What's that? Sorry, I have so much noise while rolling down the road that it's hard to discern what is what. I just plan on a bout of tinnitus after I arrive anywhere.

[jaguar68]

The engine is a +20 thou 1098 with a standard cam. The car is running a Marina air filter at the moment. As the car will be a daily driver I guess the intake noise generated by the K&N would be out of the question without extensive soundproofing.

[bmcecosse]

Only likely to be noisy on full throttle - when cruising it's little noisier than normal.

[linearaudio]

No! A K&N won't be out of the question, etc, just that if you are going to use it regularly the drone/rasp may start to annoy you! The point I was making was that the MG Metro airbox is very quiet, and won't adversely affect the power output of your engine in its standard state of tune!