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MG MG Y Type - Twin carb conversion

I am interested in converting my YB to twin carbs, I have most of the required parts, manifolds etc. However I am looking for suggestions for the exhaust system and the throttle arrangement. Is it possible to use the same exhaust by moving the box over to the right hand side of the chassis and has anyone used the same throttle cable by adding a bracket to a manifold stud for the cable anchor?
Any suggestions on air cleaners that would fit?

Any help would be appreciated.

Regards
Brian Hough
B R HOUGH

Brian,
My YB has twin carbs fitted by previous owner looks like he has fitted a TD exhaust which comes out on the near side at the back and has a larger diameter bore which makes it noisier than my YT exhaust which I fitted, purchased from NTG. The previous owner of the YB also said that the TD higher lift camshaft had been fitted without which you will not get the full benefit of the twin carbs. Check out fitting a heat shield to a YT on Pauls site to see how the choke cable best fits, my throttle cable on the YB has a home made bracket to accommodate it.
If you fit pancake air filters and a heat shield with insulating spacers you will need to adapt the Rad stay that will be in the way.
Hope this helps, good to meet up last July in Hay on Wye.
Peter
P W Vielvoye

Brian

You will need to change the front pipe to an MG YT front pipe - the rest of the system is fine. Yes it does LOOK like an MG TD but it isnt. MGOCC sell the correct front pipe I believe.

Also, do not forget to change the CAMSHAFT over for the higher profile if you are going to fit twins. The stunning extra 9 hp (45 - 54) was achieved not merely by doubling the injection of gasoline into the combustion chambers!! If you just put the twins on, be prepared to simply pour your petrol money down the drain as you will not achieve any meaningful increase in power output.

Paul
Paul Barrow

Thanks Peter and Paul (where's Mary?)

I think my idea of a manifold bracket similar to single carb setup will therefore work.

The suppliers want twice the price for YT downpipe as for a TD one (understandably), but it leaves me encouraged to try a TD one and adapt the rest of the exhaust even if it meas new clamps in a new position.

Your comments on the cam were interesting. Firstly I would say that elimination of the 'hot spot' would give improved efficiency and although the T Type manifold is not ideal it is better than the Y Type one.

But more importantly I am led to understand that the YB had the same cam as the TD (and YT although the YA had a reduced lift cam)and mine seems to confirm that.It is generally recognized to be the best general road cam, so I think my mods with a bit of porting should be beneficial.

Best regards
Brian Hough YB,TC




B R HOUGH

Brian,

I have converted my YA to twin carbs. I used the existing YA exhaust. To do this you remove the exhaust front pipe and cut of the manifold flange, after grinding of the old weld replace the front pipe into the second section with the flange loose on the pipe offer the pipe up to the new manifold you will find the exhaust pipe will go into the manfold opening when it is in the correct position slide the loose flange up to the manifold and secure with the bolts then mark the flange position adjacent the pipe or better still tack with a mig welder. Remove the front pipe and flange then reweld the flange to the pipe I had to cut of approx 1 1/2" from the top of the front pipe. I have attached a picture so you can see how I have made the throttle work. I copied the YT set up. you can also see how I tweaked the radiator stay bar to miss the pancake filters.

As for power I have just spent the weekend chasing round Lincolnshire with 50 T TYPES on their autumn run and had no problems keeping up with them after owning a TD myself for 7 years I would say the performance is very similar.

Cheers Chris

C A Pick

pic 2

C A Pick

Hi Chris

Know what you mean about chasing T Types. A couple of years ago I was in Utah with my Y and stunned a couple of T Typers as I powered past them going uphill and ran rings around them. When we got back they all came over to my car and asked what power plant I was using. I opened the hood/bonnet and showed them ... a perfectly stock standard single carburettor XPAG ... just that I had properly tuned it to account for the fact that we were up in the mountains!

LOL!!! Y Types Rule!

Paul

PS At the same show I explained to them that the Ys should not be in the Derivative Class but that TDs and TFs should be as they were derived from the Y!! That went down well ... as you can imagine.
Paul Barrow

Chris
Thanks very much for info on your conversion, looks very nice in my opinion better looking than the original setup.
Have you used long head nuts for the throttle bracket and did you change the cam as I believe the YA cam to be a little soft.
My exhaust is S/S so my MIG might not cope too well! I may have the original down pipe so I will have to look for it.
Thanks again for the pics they give me enthusiasm to carry on.

Paul
Regards performance of Y v T the data does not support you assertion ie
YB TD
HP 46 4,500rpm 54 5,200rpm
Torque 8.1Kgm 2,400rpm 8.9Kgm 2,600rpm
0-60MPH 29.3secs 23.5secs
However I concede that a well tuned YB (which I am sure you have) may well outperform a poorly maintained T Type
It also takes a brave T Typer to habitually rev to 5,200, even 4,500rpm is pushing it with these old engines!

Regards
Brian YB TC
B R HOUGH

Hi Brian,
Yes I had 2 long head nuts made to secure the throttle cable bracket. My exhaust is stainless and I had no problems welding it with the mig welder. My engine was rebuilt using a standard TD cam I don't believe you can get the cam with the profile that was fitted to the Y any more.

Good luck with your project
Kind Regards chris
C A Pick

Brian,

Thanks for the data. I actually have a standard Y Type ... as I say, just very well tuned and also I know from my rally driving days how to make best use of a gearbox too. I have no fear of taking my XPAG to the limit either and regularly enjoy passing modern cars when I am out on the freeway too. Guess I am fortunate in that I have a stock of half shafts too so I am not worried about dropping one of them either!

Paul
Paul Barrow

Attached is a picture of a Y-type (or Wolseley 14/40?) with the inletpart removed. That took some hours of sawing, grinding and filing.

I'm planning to use that on my twin carb setup, but I'm not in a hurry because the engine runs very well with a single 'polished and ported' H2.
Willem van der Veer

I am currently involved in the same exercise at the moment.

Like Willem, I have taken a standard Y(A) manifold and ground off the single inlet manifold, and replaced it with a twin carb manifold of unknown origin (it came with the car when I bought it and the casting part number is 24062V.)

I created one problem doing this - the pedestals for the manifold attachment bridging pieces went with the bit I cut off so I drilled the manifold and tapped the holes to take two bolts, to serve as new pedestals. The attached photographs will probably make that explanation a bit clearer (if I can get them to load, that is!).

The advantage of using an original manifold is that I won't have to modify my exhaust at all. Swapping the manifold and carbies will be dead simple, just disconnect the exhaust pipe, remove the single carb setup,replace with the twin and reconnect the exhaust pipe. Haven't solved the throttle cable anchor point yet but am thinking of making a bracket to attach between two head studs. That's a problem for another day!

I have a flatter oil bath air cleaner and air tube off an MG of some sort (maybe TD or Magnette?) which I an hoping will all fit without interfering with the radiator support brace
N Wakeman

Modified standard manifold with twin carb manifold.

N Wakeman

OK, I'll try again for the picture...

Willem van der Veer

As you can see in my picture it is possible to retain the original pedestals.

I have a choice in airfilters, a mesh type from an Magnette or an AC oilbath filter that probably came from a tractor, but looks suspiciously like one from a TD.

Willem van der Veer

While I can see the benefit of modifying the existing manifold, I can't help thinking that the poor exhaust flow from the centre ports (compared to the T type manifold see pic)rather negates the benefit of two carbs.

Mr Wakeman I think you have a standard T Type inlet manifold.

Looks like a technical article in the making!

Regards
Brian YB TC

B R HOUGH

Brian,

The TD manifold will flow a bit better but isn't shaped perfectly, too. Ideally the cylinders 1-4 and 2-3 should end up in pairs further away from the ports in a 2 into 1 pipe.
By removing the 'hot spot' in the Y-type inlet track the cylinder charge will be much better as it is filled with cooler air.

Separating the cast iron manifold on an A-series engine from a Mini 'frees' about 2 or 3 hp's.

BTW: I'm told that the TD air filter snorkel (as on my picture) robs 2 or 3 hp's, so why all the trouble. Because I can?
Willem van der Veer

A small point, but the outlet diameter of the T type exhaust manifold, and probably the Y type manifold, is smaller than the inside diameter of the exhaust downpipe, so a slight improvement in gas flow can be made by grinding out the exit port, where the flange is, all the way through to 42mm diameter. Any internal sharp edges should be rounded off.
I agree that the T manifold is not perfectly shaped - one problem is that ducts 1 and 4 point towards each other, thus those exhaust flows tend to oppose each other. This also applies to the Y manifold. The included angle between the outer ducts should have been less than 90 degrees.
R A WILSON

Forgot to mention that it is important to ensure that the silencer outlet tube is the same diameter as the inlet tube, which should match the downpipe. I have seen Y silencers with outlet pipes, and then tailpipes, which were smaller than the inlet pipes - thus reducing any performance with back pressure.
R A WILSON

I have tuned quite a few Y-Types over the years, both Saloons and Tourers, with single SU carbs and twin SU carbs, and in my experience there is only a minute increase in performance with the twin carb setup.

A well tuned single carb saloon will hold it's own against a well tuned twin carb saloon in all but serious high speed motoring.

If you have a good modern profile camshaft in your engine, you can see a much greater improvement in performance than what you will see from a carb upgrade alone.

So if you have a saloon engine with an original camshaft profile, you will gain nothing by fitting twin SU carbs in place of the single. As a minimum, you should upgrade to the YT/TC profile camshaft, or even better, get a modern upgrade camshaft for increased performance and less tappet wear.

Tony
The Classic Workshop
A L SLATTERY

Agree with you there Tony!

Paul
Paul Barrow

I agree that changing the camshaft is a big step forwards and perhaps expensive one, but a very cheap worthwhile alternative is to just raise the compression to 8.6 by machining 3/32" off the head. This I had done in the 1970s which enabled me to tow a 16' 4 birth caravan several times across the continent including the some pretty formidable mountain passes and all with the standard 1.25" carb. Bryan
B Mellem

And this was one, it was a big mistake but once committed there was no going back

B Mellem

This thread was discussed between 04/09/2014 and 19/09/2014

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