Exhaust/manifold on 1275 and big valve 12g940 head engine

[bluegrass]

I am looking at exhaust systems for my two morris's.

For a 1098 with 12g940 head and mg metro inlet manifold/ hif38, i am thinking of going for a converted morris exhaust manifold as detailed in the forum, and using the original exhaust system.

Is it ok to do the same thing for a 1275 midget engine with metro inlet manifold/ hif44 and big valve 12g940 head, or should i be looking at something else?

Thanks for any thoughts

[bmcecosse]

I noticed no great difference when I upgraded my 1098/940 to a 3 branch manifold, larger pipes and a straight through Cooper S silencer... It was a lot louder! A 1275 will benefit from a better system throughout - although I suggest an LCB is overkill unless you fit a longer period camshaft. I'm sure some have used the Spridget exhaust manifold with slight modification.

[bluegrass]

Thanks for the reply, i'm trying to keep things at a reasonable volume level, so i'll see what i can use .I'll look into the Spridget manifold and do some more forum searches.

[philthehill]

There were two types of exhaust manifolds fitted to the 1275cc Midget.
The easier to adapt is the one (Item No: 50 - Pt No: 12G420) in the link below) without the three studded flange.
See attached link for more details.
http://www.moss-europe.co.uk/shop-by-mo ... 500cc.html
Phil

[bluegrass]

Thanks for that. I've also found these from maniflow which i think will work.
Although an LCB, i'm hoping because its not so big, it will not be too noisy.

http://www.maniflow.co.uk/index.php?vie ... oduct=1495

http://www.maniflow.co.uk/index.php?vie ... oduct=1498

I

[philthehill]

'Maniflow' manifolds are good and delivers what it says on the can.

[bluegrass]

Thats good to hear, another issue potentially solved.

[bmcecosse]

Crrrrikey - some price.....!

[bluegrass]

Ideas of cheaper alternatives very much appreciated

I did find an already modified 1098 manifold for my 1098 project for £8 on ebay yesterday, but the 1275 midget engine project seems a more expensive proposition entirely.

[bmcecosse]

The larger bore cast manifold from a 1275 Marina actually works quite well with a 'standard' 1275 - and someone sells a large bore exhaust to go with it. There is also a twin pipe version of the cast manifold - but I think you are on your own making up an exhaust system to go with it.

[bluegrass]

OK, thanks. The 1275 will hopefully have a RCDodd RS cam, big valve head, hif44. Do you think the marina manifold would be ok with that?

[bmcecosse]

Almost certainly - that's not a 'long period' cam - just a cleverly designed high lift cam specifically intended for good torque.

[bluegrass]

Ok. Whats an example of a 'long period cam' and is it applicable to my setup, or am i better off sticking with the ac dodd type ?

Thanks

[bmcecosse]

He will sell you a long period cam - but it's designed for high revs/maximum power and of course requires engine balancing and strengthening....and very 'intractable' about town. And of course there are cams in between. His RS cam gets great reports and I think you will be well pleased with it.

[bluegrass]

Yes, i think you are right..... Its good to understand what a long period cam does, but its not for me. I'm looking for a nice reliable road car.

[bmcecosse]

The long period opens the valves earlier and closes them later - with some considerable overlap when the inlet valve starts to open before the exhaust valve is closed. Maximises air flow through the cylinders at high revs....but wasteful on fuel and poor torque at low revs.

[bluegrass]

Thanks for the explanation....Slowly but surely I'm geting to grips with all this.