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MG Midget and Sprite Technical - 1380cc engine advice sought

Hi

Anyone built, set-up and run a 1380cc (offset bore) engine and has words of wisdom to share please?

I am looking at a buying a secondhand ‘fast road’ 1380cc which is under a bench out of a car which I know is a risky thing - if I can do a compression check that would be good and buy an endoscope to see if I can spot bore scoring; hoping for the best on the bottom end! At least the engine was built by Agra Engineering including machining.

If the engine proves worth a punt (and then pull the head and check the bottom end and a mild refresh) what advice do you have on carbs, distributor? It apparently ran a single twin choke sidedraft 40mm choke carb (guess a Weber DCOE 40) - anyone tried twin SUs on a 1380cc (have some twin 1.5 inch MGB HS2 SUs on a Maniflow midget manifold as well as twin 1.25 inch HS4 set up)? Any needle and spring thoughts to get it going?

Use a Aldon red or yellow distributor? The cam profile is unknown.

Once running I would take it to Peter Burgess for a proper rolling road set up.

I know this is a gamble as if it needs a rebore then there is only 1430cc left and this is no good as car needs to be no more than 1400cc to fit in roadgoing hillclimbs class in Scotland.

Cheers
Mike
M Wood

I'd think a 40 would be too small for a 1380, had a mate that ran a 1380 in his mini on twin 1 1/2" SU's and it ran great ,strong as an oxx from down low right up through the revs into the red. If you were thinking weber you need a 45 with 38/40 chokes to make it GO properly.
As far as the dist. advance curve goes that'll depend on how angry the cam is mostly. Also, Weber carbs tend to need a few extra deg. of initial advance compared to SU's
Agra Engineering would probably have recorded the specs of the engine, might be worthwhile contacting them, and then decide on your carb choice before you splash out on a distributor to suit your setup

IF you run the 1 1/2" SU's a reasonable/safe starting point would be something like BG needles and BLUE damper springs---that should be fairly close, a tiddle rich(safe) if anything but should drive fine until you get to Peter.

willy
William Revit

Yes I agree with William I had a 1380 and it ran well on a 45dcoe (even better on split webers but that's another story!) Twin 1.5 SU's are fine as well and tend to be more flexible when used as a road car. You will need the cam profile to know which distributor to use
Bob Beaumont

Willy and Bob

Many thanks for your very helpful advice.

Very best wishes
Mike

M Wood

Mike,
If you go twin SU's I would suggest fitting an AFR gauge (preferably a duel set-up) to really see what's going one re the combustion.

It would be devastating if you were to bore wash it on the way down to Derby and if it were me, I would consider transporting it just in case.

I'm planning on making an external AFR tuning set-up if you want to do a quick check before heading down to Peter?

Defo interested to see how it turns out as I might do similar to my MG1300 one day ;0)

Best of....
MGmike


M McAndrew

This thread was discussed between 25/06/2026 and 27/06/2026

MG Midget and Sprite Technical index

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