1275 exhaust manifold questions....

Common upgrades - A-Series mods, brakes,wheels, handling, interior.

1275 exhaust manifold questions....

Postby Giz » Wed Mar 12, 2014 1:00 pm

I've placed this question in my restoration thread but fell it may be lost in there so have decided to post separately.

I'm in the process of upgrading the engine and gearbox in my 1958 saloon with an MG 1275 setup. This includes the carbs and will therefore result in a change of exhaust manifold setup too....

On fitting the MG exhaust manifold I've noticed it's longer and at a different angle than the original Minor one, therefore a 'standard' Minor exhaust will not fit and give clearance. I can't be the only person who has ever tried this and have looked over the net for solutions. Having also checked my shed I have found two other Minor manifolds, 948 two piece and a 1098 standard, I have come to the following three options....

1) remove the inlet from the 948 two piece and fit the exhaust bit to the engine, therefore 'standard' Minor exhausts will fit..
2) cut off the inlet from the 1098 manifold and fit it to the engine, therefore 'standard' Minor exhausts will fit..
3) keep the MG exhaust and source a down pipe that will allow the fitting of a 'standard' Minor front box and remaining pipe..

I'm not sure that 2 gives me anything over 1 but am happy to be corrected. The MG exhaust looks to be a larger bore so may be the 'better' option if a down pipe can be sourced..

Alternatively I can get the three branch 'Ital' manifold but that adds £££'s on the bill and I'd rather spend the money on something other than a manifold I have three of, unless there is going to be a significant sound / power difference...

While on the subject of exhausts which system is currently seen as 'the best' for quietness and power?

Any help, guidance, past experience, etc with exhaust manifolds and systems, as I need to get a complete setup for the car, gratefully received...
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go with 1, to get up and running

then try to get a 1275 mini manifold with hs4, this will go straight on morris exhaust,

if you want big bore its a 3 branch and hif38 check out chris ryder he has this system and i think mm has aswell

just check that the 948 and 1098 have same size ports, use the larger one,

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Re: 1275 exhaust manifold questions....

Postby Giz » Wed Mar 12, 2014 6:18 pm

Thanks for the prompt response, the ports are the same size on the 948 and 1098 exhaust manifolds so no difference there. I want to keep the twin SU's if possible, it all about the look, but could be swayed if a larger single unit can deliver better economy without the loss of power.. Loads to read up on that then perhaps one day, but for the time being I think I'll want the twins, until the balancing gets to be a nightmare....

Thanks again...
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A midget exhaust won't fit a Minor without a fair bit of work. You can buy the correct exhaust manifold for a Minor, but using the exhaust manifold from a 948, or a sawn off one from a 1098 is an acceptable way to go.
Twin SU's give similar performance to a single 1.5 inch carb, but need a bit more fettling to keep in tune - look better though.


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Re: 1275 exhaust manifold questions....

Postby Giz » Fri Mar 14, 2014 8:13 pm

Just to finish this one off in case anyone is looking at this in the future with a view as to which option to choose.

Go with option 2. This is due to the finish you can get with the 1098 manifold after grinding the remains of the inlet bits off. It's far better than having to make a cover plate, as the two piece opens a hole onto the exhaust manifold when opened, the ledge that sticks out and the inevitable broken studs.

Thanks for the help everyone, I now have a decent looking exhaust manifold that will work with my twin SU and, I'd guess, other inlet manifolds...

Thought I'd add a couple of pics to show the two.

First the 948 two piece;

Image
DSC_7679 by petergisby, on Flickr

Image
DSC_7681 by petergisby, on Flickr

The the modified 1098;

Image
DSC_7683 by petergisby, on Flickr

Image
DSC_7684 by petergisby, on Flickr

Thanks again...
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Re: 1275 exhaust manifold questions....

Postby bmcecosse » Wed Apr 23, 2014 10:31 pm

Yes- that is the standard way to do it. I have used an MG 1100 3 branch - slightly 'adjusted' to keep it tight to the engine so it slips down the inside of the chassis leg. Forget the twin 1 1/4 SUs - they are no better than a single 1/1/4" SU on a GOOD inlet manifold. The only advantage is the elimination of the hot spot - which you have done. If you think about it - each cylinder breathes independently of the others - so for more air flow you need a larger carb. Go for a single 1 1/2" SU - HIF38 if you can get one - with an AAA needle... It works!
 









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Re: 1275 exhaust manifold questions....

Postby MM » Thu May 22, 2014 9:08 am

pfgiz wrote:It's far better than having to make a cover plate, as the two piece opens a hole onto the exhaust manifold when opened, the ledge that sticks out and the inevitable broken studs.

First the 948 two piece;

Image
DSC_7679 by petergisby, on Flickr

Image
DSC_7681 by petergisby, on Flickr



What "inevitable broken studs"? :? Once you've bolted the cover plate on, you tend to just leave it on! I've used this setup on mine for years with no problems, with various carb setups including twin 1.25" SUs, and latterly, a HIF 44. It works pretty well.
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Re: 1275 exhaust manifold questions....

Postby Giz » Thu May 22, 2014 10:30 am

MM wrote:What "inevitable broken studs"? :? Once you've bolted the cover plate on, you tend to just leave it on! I've used this setup on mine for years with no problems, with various carb setups including twin 1.25" SUs, and latterly, a HIF 44. It works pretty well.


The studs that break off in the exhaust bit of the manifold when you try and remove the inlet bit of the manifold. These need to be removed before a plate can be secured. Not the case for the 1098 manifold which just needs the inlet bit grinding away.
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Re: 1275 exhaust manifold questions....

Postby MM » Thu May 22, 2014 10:47 am

Oh, I see. I don't think mine ever came with the alloy inlet section attached, so I didn't have that problem. I fitted the blanking plate with some new bolts, which have been fine for yonks now.
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Re: 1275 exhaust manifold questions....

Postby geezer » Thu Feb 11, 2016 2:00 pm

The Midget exhaust manifold will fit the Morris Minor chassis. See this link.

viewtopic.php?f=13&t=10987
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