What exhaust for Marina 1275?

[nkm198]

Apologies if I'm covering familiar territory here, but I'm confused about the best way to improve the performance of my 1962 Traveller. It has a 1275 from a Marina, 5-speed Type 9 box and 3.9 rear end, electronic ignition and electronic fuel pump. It currently runs the ancillaries fitted to the original 1098 motor. Although it's very economical, I appreciate that this set up is limiting the output of the bigger engine, and in fact since fitting a new mild steel exhaust, power has been down significantly – third on hills I previously climbed in fourth, and so on. Should I look for a standard Marina manifold and HS4 carb? If so, do I then need to replace the standard minor exhaust with a bigger bore system? And which air filter? I've been through lots of threads on the forum and I can't work out which solution is best. All advice gratefully received!

[midget]

Yes to the HS4 and a Maniflow LCB exhaust, then get it set up properly. All off the shelf off ebay. If you need more, get the head flowed either yourself (read Clive Tricky's book) or professionally.

[philthehill]

The cheapest way is to replace the HS2 carb and existing manifold with a Marina HS4 SU carb and Marina inlet/exhaust manifold.
ESM sell a adapter pipe to join the Marina exhaust manifold to the Minor exhaust - fitting a larger dia exhaust pipe would help.

http://www.morrisminorspares.com/engine ... pe-p830089

http://www.morrisminorspares.com/engine ... el-p830087

https://www.ebay.co.uk/itm/CLASSIC-MINI ... SwAHtaAr6E

Use the Marina air filter.
https://www.ebay.co.uk/itm/Morris-Marin ... SwcC9Zrah1

If you keep everything Marina you will have less trouble setting everything up which can be a problem especially if you have a mix and match engine assy.

[nkm198]

Thanks for the quick replies, guys. I’ll look online for a standard Marina inlet/exhaust manifold and hs4 carb. Presumably I could use the standard Marina air filter? And even though the exhaust system on the car was new (for the MoT) it would seem sensible to do the job properly and replace it with a bigger bore system.

Midget, if I used the Maniflow LCB exhaust manifold (or ESM or BM equivalent) instead of the standard Marina combined inlet/exhaust manifold, would any A Series inlet manifold suitable for an hs4 carb do the job? Say, a mini inlet manifold.

Sorry for so many questions! The car is very long-legged and comfortable at motorway speeds, but it is probably a little over-geared for the power available.

[philthehill]

As regards the exhaust manifold - unless you have fitted a camshaft with a longer valve overlap - fitting a multi-branch manifold is a waste of money. Looks good though.
Unless you get the multi-branch exhaust manifold mated to all the right parts you can suffer a power loss and be worse off
The multi-branch exhaust manifold effectively stops the exhaust gases backing up (as it has further to travel) and going into the adjacent combustion chamber which is what would happen if you had a standard exhaust manifold and long overlap camshaft.
The longer the valve overlap the longer the pipes required before they join up as one.
This is when you need a multi-branch exhaust manifold - 310 scatter profile cam & 1.5 ratio rockers fitted and very very big valves.

[midget]

Would hate to argue with Phil I know that he is far more knowledgeable in tuning the a series than I am, but these mods that I suggest is all that has been done to mine, and it has dramatically improved the performance.
This was proved with a session on the rolling road, which is why I stressed getting it all set up properly.
These mods will surely improve the gas flow through the head along with other advice given in the Vizard/Trickey manuals whatever cam/valve C/R you have?
Of course there are a multitude of (expensive) tuning that is possible, but the post was for, I think a kind of Stage 1 mod?
Forgot to add a better inlet manifold as well. Mine is a Howley, but there are others.

[nkm198]

Spot-on, midget - i’m Just looking for a simple upgrade. It’s a bit silly swapping to a bigger engine then stifling it.

The car’s a daily driver, mostly short local trips with the occasional long motorway run. There are a lot of hills here in Cornwall!

As ever, this forum has come up trumps (though I still keep expecting BMC Ecosse to pop up with an informed opinion).

Thanks again - I’ll let you know how I get on.

[philthehill]

John
You are absolutely right in that done as a package and put on a rolling road there can be a vast improvement in performance.
The problem is that just putting a multi-branch manifold and a larger carb onto the engine may not necessarily reap any benefits.
If a cost benefit analysis is carried out the cost of improving the engine against benefits may not be very favourable. If cost is not a problem then the world is your oyster.
As I suggested above fit all Marina parts and all the compatibility problems have been worked out for you by BMC/BL.
Having the right Marina 1 1/2" HS4 SU carb (instead of the HS2 1 1/4" SU and the wrong manifolds) and the right exhaust/inlet manifold will reap benefits without having to break the bank.
Personally I would not fit a multi-branch exhaust manifold unless it was matched to a performance camshaft.
For example putting a multi-branch on a standard 1098cc 'A' series reduces the scavenging effect of the exhaust gasses and power is lost.
PS
Rolling roads are the way to go for ultimate performance as even the correct settings as stated in the workshop manual can see loss of power.
Phil

[midget]

Phil
Agreed of course, but concerning the exhaust--- Why then did the A+ engined Ital(the last incarnation of the A series) have a cast twin outlet exhaust manifold if it was not for an upgrade?
As you say BL/AR (? ) have done the work for you
I remember from my Mini owning/tuning days that the Cooper exhaust manifold (with all the rest of which I mentioned) was a massive upgrade.
They sounded nicer with a Peco box too

[philthehill]

John
The twin down pipe exhaust was introduced as part of a package for the later 'A' Series to reduce the amount of pollution and vapours produced by the 'A' Series engine.
The package comprised basically of improved electronic ignition (even later versions had no distributer) with crankshaft sensor, improved SU carb latterly with variable electronic mixture control, fuel flow transducers, charcoal filters on the fuel system etc. etc.
For the Americas market the cylinder head was even fitted with air injection ports and even more gadgets to improve efficiency and so reduce pollution. But in the end it reduced the power output of the engine.
For later Ital engines there was a very small increase 4 - 5 degrees in exhaust valve opening before BBDC with a similar reduction in exhaust valve closing ATDC. That small variance would not normally require the twin pipe manifold but as part of the overall package it was of benefit and including all the various modifications all interconnected and working together improved engine efficiency and reduced the pollution levels. All these improvements were developed by BMC/BL - so to me there is no point in trying to reinvent the wheel - better to just fit the parts as developed and fitted by BMC/BL to the 1275cc Marina engine and be done with it. It is the most simple solution and its cost effective too even if the vehicle is not put on a rolling road to get everything exactly right.
I know the Cooper exhaust manifold well - I had a modified Cooper S 1275cc exhaust manifold on my A35 in conjunction with a Weber 28/36DCD and latterly used on the minor with a H4 SU carb Minor and Maniflow/Janspeed fabricated inlet manifold. The Cooper long branch manifold was used in conjunction with the Cooper camshaft which had greater overlap than the standard Minor item and so needed the longer exhaust pipes - but they were not that long (see link below) just long enough to stop the back flow to the adjacent cylinder. Camshafts supplied by BMC/BL special tuning that had huge overlaps needed exhaust manifolds with extremely long primary and secondary pipes to stop the back flow and to assist in scavenging the cylinder.
I had the Sprite 1098cc straight through exhaust system fitted to my 998cc Minor which helped the gas flow and sounded well with a nice resonance and bark when going between buildings.
Going back many years the Minor on the track ran with no silencer just a straight through pipe from the multi-branch exhaust manifold exiting at the rear and that sounded lovely - oh those were the days
To sum up and as described in Clive Tricky's book Tuning the Mini if you run a 'vigorous camshaft' it is recommended that a multi-branch exhaust manifold is used. Similar comments are given in the Vizard book on tuning the 'A' Series.
Classic Mini Cooper style long branch tubular exhaust manifold for use with Cooper camshaft:-
https://www.ebay.co.uk/itm/Classic-Mini ... SwEOpZ6y7A
Phil

[midget]

That's the one I had in the past. Didn't think that they were still available, so grab it. Looks ok with a clean up.

[panky]

Wouldn't that be too long to fit in the Minor engine bay? I struggled with a standard Midget one.





If the OP wants to go this rout I used a Mini alloy inlet manifold and a HS4 with a K&N element in a Mini air box. The Midget exhaust manifold is attached to an 1 1/2" 'Sports' system from David Manners (not the quietest system in the world) with a modified down pipe to fit the manifold.
This is on a 1098 with a 12G940 head so you might want to go up a size with the carb and go for a HIF44 - but a HS4 should be fine (and a LOT cheaper)

Before I got the Midget item I used a combined inlet/exhaust off a Mini



I did notice quite a difference when I fitted the alloy inlet and Midget exhaust.

[Andy W]

My 1275 Marina engine has:

HIF44 carb on a Mini-Spares inlet manifold.
This came from a Metro & needing no rejetting, etc, just some minor tweaking.
I have the David manners Group 1.5" diameter complete exhaust system (inc. the manifold as no Midget exhaust ones were around at the time & also as using the whole DMG exhaust, it all fits together seamlessly.
Standard gearbox but a 3.7 diff.
Runs much better, esp. as I do a lot of long distance trips.
Didn't come cheap but it was worth it!
All the fuel & exhaust mods were recommended by Panky who gets credit for guiding me through the minefield!

[panky]

Stop it

[midget]

Wouldn't that be too long to fit in the Minor engine bay? I struggled with a standard Midget one.

I had this on a Mini, but would a bend at the bottom tight up against the Y piece not suffice? Any one tried it?

[philthehill]

When I had the Cooper exhaust manifold on my Minor I had to cut and reform the bottom of the manifold and turn the exit pipe through 90 degrees to the rear.
I also had for clearance to cut the front chassis rail lip where it is spot welded and re-weld the vertical and horizontal metal continuously.
The exhaust pipe then ran a similar route the Midget/Sprite.
The Cooper manifold was utilised as the Morris Minor LCB manifold was not in general circulation. We are very lucky these days as most of the work is done for us and there is a good selection of tuning parts - back in the late 60s early 70s if you wanted it you made it or adapted something similar.

[Declan_Burns]

I have recently fitted the Maniflow LCB combined with the large bore exhaust from ESM on the 1098 engine with the 940 head and HIF38 carb. The power increase is indeed very noticeable and I am very pleased with the results. I had intended fitting my rebuilt 1275 but might not even bother. It goes like the clappers as it is!
The ESM exhaust is not a good fit and in my opinion the bend over the rear axle is too acute so that there is very little clearance between the top of the bend and the bodywork. The rear silencer has very little clearance between the tank and the damper and the tailpipe is a tad too low.
Regards
Declan

[philthehill]

Declan
Which Morris Minor Maniflow LCB manifold did you use as there are three listed?

http://www.maniflow.co.uk/index.php?vie ... tegory=209

I would suggest that your power increase is obtained by utilising a tuning package of head, carb/manifold, exhaust manifold/exhaust pipe - the same sort of process undertaken by BMC/BL to improve the 'A' Series that metamorphosed into the 'A' Plus engine.

Quite a few of the improvements to the 'A' Series over the years came from developments made for and utilised in the 'A' Series Formula Junior racing car engine.

Phil

[don58van]

Declan

Further to Phil's questions:
Do you have a standard 1098 cam or an performance one?

Don

[Declan_Burns]

Phil,
I am using this manifold:
MORRIS/MINOR 1000/1275 EXH MANIFOLD (LM053)
http://www.maniflow.co.uk/index.php?vie ... oduct=1495
This is the exhaust:
http://www.morrisminorspares.com/engine ... pe-p830089

Don,
I assume it is the standard cam but I have never taken it out to see.

Regards
Declan