Morris Minor Owners Club

Been out fitting the new exhaust, and I've hit a serious problem.

The manifold clamp included by the $well_known_spares_company doesn't fit the manifold and the one I took off the car doesn't clamp the exhaust. Comparing them, I see that the two differ in diameter by nearly a centimetre.

What the hell's going on? The old exhaust is gone to the tip, but I can't recall that it looked any different to the new one (apart from the new one being stainless). The engine is a Midget 1275, but the manifold looks like the standard cast-iron combined one. I can't see a difference between it and the one on my 1098 saloon.

What do I do now? Any clues?

1275 has a bigger manifold outlet and needs to mate to a bigger diameter exhaust pipe. Get it back from the tip fast!.

use the other clamp?

Matt - I think Jim needs a big diameter exhaust system toi match up with the bigger outlet on the 1275 exhaust manifold. The stainless sytem he has will be too small to be held by the original clamp - and will strangle the engine horribly anyway!

The other exhaust was the same diameter as the new one, i.e. about an inch-and-a-bit. That was right from the manifold back.
Alas, it went to the tip yesterday, just before I found that the "fitting kit" was one mounting clamp short

Neither clamp fits. I guess the new clamp might hold it on, but it would only be using a very small area of the exhaust end. Doesn't seem good enough.

And Wifey doesn't want a large-bore system, as she wants the farty noise to stay.

Well - the reason IS that the oulet on the 1275 manifold is larger - designed for a larger diameter exhaust - so the original exhaust must have been hanging on there by a wing and a prayer. For best power you should be getting a larger diameter exhaust system. There was a thread about this a while back - when I tried to 'urge' some of the suppliers to have a batch made up! A front pipe for a Marina should fit - then make up the exhaust to the rear on that pipe.

So is the manifold the 1098 type or 1275? measure the internal diameter of the outlet. I probably have a clamp you can use somewhere

But the small diameter exhaust will strangle the 1275 engine !! If you REALLY want to use that exhaust then you should fit a 1098 exhaust manifold - which will match the clamp and the exhaust - but a larger bore system would release about 5 extra horses!

Mr Ecosse we have all had this discussion with Jim ;)

So - why is it turning up on here if the answers are already known!! Big engine needs big exhaust - it's simple!

bmcecosse wrote:But the small diameter exhaust will strangle the 1275 engine !! If you REALLY want to use that exhaust then you should fit a 1098 exhaust manifold - which will match the clamp and the exhaust - but a larger bore system would release about 5 extra horses!

Matt's right when he says this discussion has happened before. I know that the current induction and exhaust system is spoiling the engine, but Wifey insists that she doesn't want it changed because she likes the sound.

What the engine needs is a HIF44 through an alloy inlet, then out to a decent exhaust system. What it gets is the HS4, combined manifold and a peashooter "because it sounds nice".

So, I get to work out how to attach the tiny exhaust to the manifold. I know that if I say it can't be done, Wifey will (not unreasonably) ask why not as it clearly has been so before.

So - why is it turning up on here if the answers are already known!! Big engine needs big exhaust - it's simple!

Because at least one of the 1275cc SADMOG cars is running very well with a standard bore system.

Jim I may have a manifold and exhaust that you could use that will run with a 1.5 inch SU (not HIF38 or 44) What carb do you have?

Jim

Might be able to come and have a looksy for you tomorrow eve. Drop me an email mh_0AThotmailDOTcom ;)

Peetee wrote:Because at least one of the 1275cc SADMOG cars is running very well with a standard bore system.

Indeed, our Trav And Rob's?

Jim I may have a manifold and exhaust that you could use that will run with a 1.5 inch SU (not HIF38 or 44) What carb do you have?

The carb is a 1.5" HS. The mounting bolts are diagonal.

There will be a standard-size stainless exhaust going spare, I should think

Could an exhaust shop, that can fabricate their own, make an adapter to go from big flange/pipe to std smaller pipe?
Also, I had mine replaced a while back by an exhaust shop that made the whole system. The new size was 1½". This matches the bigger bore manifold I have. It flows well and still makes "the noise."

You can buy adapters in various sizes which might do the job - I think I'm gonna have to see if I can get hold of one from 1 12/2 inch to pea shooter as I can't afford a 1 1/2 inch system just now, and would like to use my 1 1/2 inch LCB - well, either that or the Marina manifold/downpipe that's on there atm

somewhere I have a Mini 1000 manifld that has a fitting for a 1.5 su on one end and a Minor sized exhaust at the other.
Is that what you are after?

Peetee wrote:somewhere I have a Mini 1000 manifold that has a fitting for a 1.5 su on one end and a Minor sized exhaust at the other.
Is that what you are after?

I reckon that would do it. When can you confirm/deny the existence of said manifold? ;-)

Roni, that's a decent idea (and Maniflow are close by here), but getting stuff custom made sounds expensive.

BG, do you have a known source for these adaptors? That sounds like it would solve the problem in the easiest possible way.

Mini inlet/exhaust manifold will fit - it loses you about 3 bhp because it heats up the ingoing charge, and the small exhaust will lose you 5 bhp. But hey - if that's what you want - do it! Of course it will 'run' - it would just run so much better if it was done properly.

Because at least one of the 1275cc SADMOG cars is running very well with a standard bore system.

I was very surprised how well mine went when iI did that. I figured that there was no way it could have power at high revs due to the pea shooter exhaust... (with 1.5" carb)
But it didn't drop down from ~80mph up a long hill hill where the previous 1098 had always dropped to ~60mph. I was gutted that the big ends only lasted 3 weeks on that engine caused by blocked oilways (sludge from previous owners lack of servicing)