948 Distributor on 1275 engine

[DMNewton]

Hello Folks.

I've just finished installing a 1275 midget engine and gearbox to my 1958 Minor. I have also fitted a HIF44 carb and manifold from a Metro. The fue pump is new, as is the coil, but I have transplanted the original 948 distributor (points changed about 10,000 miles ago). I setthe static timing and have got the car running OK-ish on the driveway, but despite the engine sounding very smooth there seems to be a slight mis-fire both at tick-over and higher revs. When I take it out for a spin, that's when the problems really start as the engine splutters and dies at about 45+mph unless I get off the accelerator again.

So my questions are, are the mis-fire and dying at speed related, and are they both due to the use of the original 948 distributor? Or do I just need to spend more time fiddling with the timing and fuel mixture?

Thanks in advance for your help

[bmcecosse]

It's obviously not the ideal dizzy for a 1275 engine...and is the vacuum advance working anyway? What did you set the timing to? Have you optimised it at idle speed? I strongly advise a NEW 45D dizzy from the likes of Accuspark... And -what needle is in the carb?? Why a 44 size carb - has the engine been modified in any way ?

[les]

Why not fit a midget distributor anyway. That way you can eliminate it as the cause.

[DMNewton]

Thanks for the quick response bmc!

I'll check the vacuum advance is working - not looked at that yet. I have to be honets, I haven't measured what the timing is set at. just got it in the ball park statically, then rotated the dizzy while it was idling to get the highest revs at tick over. I guess that isn't the best way to do it. What would you recommend it be set at? I've borrowed a strobe gun, so I am hoping to make amore scientific job of it at the weekend.

If I get a 45D, would it be worth having electronic timing, or just stick to points?

Its a long story, but the old carb and filter were no good, and needed a good deal of refurb or replacement. The HIF44 was going begging, so I've used that. I don't believe the engine is modified in any way, but if there is some way of checking I will have a look. I also don't know what needle is in the carb. Is there some way of identifying it?

Sorry for all the questions - by way of explanation I've owned the car for 27 years but it hasn't been on the road for the past 10 or so. The person looking after it for me put it in the garage 10 years ago and just left it there without draining or turning the engine, handbrake left of etc. so pretty much everything was in need of a lot of attention. I want to use it for everyday use again, hence replacing the seized 948 with the 1275 etc. but this is my first venture into modification from the standard.

[DMNewton]

Hi Les, If using the 948 dizzy is the cause then I will change it for a midget one. I must admit, I didn't think it would make that much difference, but I'm learning all the time.

[bmcecosse]

An ancient 948 dizzy will be well worn by now - and will not have a suitable advance curve for a 1275.. And it will be a miracle if the vacuum advance is still working. You have absolutely set the timing correctly - there is no point trying to set it with a 'strobe' - what will you set it to ???? I would go electronic -these new dizzys are well regarded. The needle is stamped on the shaft with the profile code. Metro dizzies are notoriously weak set - for best 'emissions' and economy. You could try a BDL needle for best performance, although not necessarily best economy.

[mike.perry]

If you are fitting a 1275 engine in to a 948 car then I hpoe that you are uprating the brakes

[DMNewton]

Thanks again for your help. I'll make the necessary purchases and adjustments, and report back

Mike, Yes, I've fitted the ESM front disc kit, plus servo, so much improved stopping! I don't have to open the quarter lights to assist with braking anymore . The brakes were my first priority, before the engine, as stopping was allways more of an issue than going.

Cheers again all.

[DMNewton]

I just had a look around for 45D distributors, and they all appear to be negative earth. The 25D is positive earth, which I need, so would that be recommended? A quick look on other forums suggest that the 25D is very similar, but tuneable. Any thoughts?

[philthehill]

When I changed my Series 2 (fitted with a 1098cc engine) from Positive to Negative earth when installing an alternator it had/made no impact on the operation/performance of the distributer.
Because only Negative distributers are available there should not be a problem.

[bmcecosse]

As above - go negative!

[DMNewton]

Thanks for all the advice. I'll get a negative earth 45D on order. It would be helpful if the accuspark adverts didn't all say -be Earth only. Good to be re-assured by you chaps that it will work ok on Boris!

[James k]

Have you ordered an electronic one? If so then your car does need to be negative earth. If it's currently positive then it's very easy to switch over.

[philthehill]

The thread starts with discussing fitting/problems with a normal (non electronic) Minor distributer to a 1275cc engine but if you are going to fit a Negative earth electronic distributer yes you may well have to change the cars electrics to Negative earth.
Changing the cars electrics to Negative earth is quite a simple task and is well described in the Owen Burton Marina to Minor booklet.

[DMNewton]

Thanks again. Whilst thinking about it this evening I came to the conclusion that it would be a safer bet to change to -ve earth, so this confirms it. Thank you all.