Morris Minor Owners Club

Hi

Apologies up front for the rambling post...

I recently purchased a '68 Traveller. When I test drove it it was pinking a little, I asked the owner to have his local garage adjust the timing and look at the brakes as they pulled to one side. That was all sorted and I drove it back from West Somerset to Sussex a couple of weeks later:D

Piecing together the spec from a thick history file it seems I have:
1275 Ital engine bored out to 1300
Maxiflow I head
6648 CAM
Howley inlet manifold
HIF44 carb
Freeflow exhaust manifold.

It all runs very sweetly but ever since I've had it, when I switch off when hot, it runs on for a few seconds ('pre-ignition' I believe).
It recently had some MOT work done and the mechanic slowed the tick-over down and adjusted the mixture slightly leaner. This had the adverse effect that it needed a lot of choke to start and bit of choke pretty much all the time and didn't pull so well from lower revs but cured the pre-ignition. This seems counter intuitive to me, I thought pre-ignition was generally a symptom of an overly lean mixture.
Today I adjusted the mixture slightly richer and hey presto, starts instantly with no choke needed, pulls better from low revs but the pre-ignition has returned..

Any thoughts/suggestions from all you gurus out there?

Cheers
Dave
PS. I'm thinking a K&N cone air filter might be a good move, any thoughts on that with the above setup?

Hmm -well, never heard of a 'maxiflow' head - is it attributed to any tuning firm? And a 6648 cam is an unknown item too.... If it is a '648' cam (also known as '649') then that is a Race cam and entirely unsuitable fora road engine.... Pre-Ignition is 'Pinking' heard when the engine is accelerating hard in the gears, and very bad indeed. Do you have this? What you describe is 'running on' and yes it is caused by carbon glowing red in the combustion chamber - entirely likely with over-rich mixture. The car SHOULD need some choke to start from cold - but then of course it can be pushed in after a few seconds. Any idea what needle is in the carb ?

Maxiflow appears to be associated with Vulcan - who specialise in Ford engines - but do offer (expensive!) heads for 1275 Metro engines. The Maxiflow 1 appears to have a larger inlet valve - but standard exhaust.

Correct, the head was from Vulcan engineering (£138 + VAT in 1990).
The cam looks like it might be a standard MG Metro cam (see: http://www.pistonheads.com/GASSING/topi ... oice+query), part number CAM 6648, £86 in 1990

Thanks for the clarification of the terms, what I have then is running on, not pre-ignition and therefore suggests I'm running too rich. I will try leaning if off a touch and perhaps just speed up the tickover a bit...

The needle (from the receipts) seems to be part number AUD1005 which appears to be 'fixed need no. 6' (http://www.minispares.com/product/Class ... D1005.aspx) whatever one of those is!?

Thanks for your help

Dave

That's a MUCH more sensible cam - ideal in fact. The usual starting needle for a set-up like that would be the BDL. And yes a GOOD air filter can make a world of difference. Never heard of the MG cam listed with that number - it's the 'new' thing I've learned today !

OK, I'll look into changing the needle. I don't really understand the multitude of needles and how a 'fixed needle no.6' compares to a BDL but looking at this chart: http://www.7ent.com/pages/su-needle-chart-pg-87.html suggests that the 6 or even the H6 are way up the rich end of the scale compared to BDL?

Extensive googling backs up your BDL suggestion for my setup and nowhere can I see 'fixed needle no.6' recommended

Apart from at tick over, is it the needle alone that controls the mixture or is it a combination of the two across the RPM range? If I change the needle and switch to K&N filtering, is it then a juggling act with the timing/mixture to get the setup right and is this perhaps not a job for a novice?

I'm not looking to race this thing but I'd like to get the best out of the setup I have 'inherited' without it being difficult i.e. this is meant to be my daily driver so I'm willing to trade performance for ease of use (but I do like the fact it has a bit of zip to it ).

You say you have an HIF 44 -which uses a 'swing needle' which the BDL is....a #6 is indeed a fixed needle and won't fit that carb. Take the bell off and inspect the needle to see what you really have. And yes - the taper profile of the needle determines the mixture throughout the rev range, and has virtually no influence on the idle mixture, which is set with the scre adjust on that carb. That does however have an overall slight effect on the running mixture, so it's important to set it correctly. Ignition timing is also important of course (and can also cause 'running on' if incorrect) ....set it for 'best idle' then check there is no 'pinking' under load.

Thanks so much for this, I will do a lot more reading and then get my hands properly dirty!

Looking here: http://www.theminiforum.co.uk/forums/to ... do-i-have/ it seems I do have a HIF but whether 44 or other size I don't know. Looks like I have to take the carb off the engine and measure the throat to be sure? Even then, telling a HIF6 from a HIF44 means sub-mm accuracy but then maybe they're so similar it makes no difference 'needle-wise'...

Looking again at the old hand-written (scrawled) receipt it looks like 'HIF44 1409' and good old Mr Google came up with this: http://sucarb.co.uk/carbspec/carburetto ... s/id/1442/

First off is to establish I really do have a HIF44 - I know a previous owner bought one but honestly, it could be anything on there now for all I know!

So much to learn and so much scope for cocking up!

OK, I whipped the bell off this evening. From what I'd seen on the web I was expecting to then lift off the spring then withdraw the piston but the piston came off with the bell. All looked pretty grubby in there but the piston slides up and down smoothly enough, will get some carb cleaner and give it a good going over at the weekend maybe

Anyway, the needle is a BBZ which I see recommended here and there for a stage 1 1275.. Is mine stage 1, who knows...?

I've leaned the mixture off a bit and will see how it goes, looks like I'll need to just keep twiddling. If decent running continues to result in over-run then I guess I should change the needle...

Cheers
Dave

I find this sit vey helpful in comparing and choosing needles. Choose your carb from the top and then select your existing needle from the drop-down, you can then add more and compare their properties. SU needles are measured for thickness at 'stations' which are spaced out every 1/8" along the length - basically the higher up the graph the richer the needle.

http://www.mintylamb.co.uk/suneedle/

Dave.Sellers wrote:OK, I whipped the bell off this evening. From what I'd seen on the web I was expecting to then lift off the spring then withdraw the piston but the piston came off with the bell. All looked pretty grubby in there but the piston slides up and down smoothly enough, will get some carb cleaner and give it a good going over at the weekend maybe

Anyway, the needle is a BBZ which I see recommended here and there for a stage 1 1275.. Is mine stage 1, who knows...?

I've leaned the mixture off a bit and will see how it goes, looks like I'll need to just keep twiddling. If decent running continues to result in over-run then I guess I should change the needle...

Cheers
Dave

The stage 1 Mini kit comprises of a new needle, K&N air filter, alloy water cooled inlet manifold and a free flow exhaust with LCB, the head and cam are unchanged. Yours sounds more like stage 3 of 4 .

At least you have confirmed it is an HIF44. And yes on Minty - when you compare the needles , there is very little difference - so I would stick with the needle you have, and just fine tune the idling. You can also try thinner/thicker oil in the carb dashpot.

Thanks all.

I think I'll have the carb off, give it a good clean, refill with the 'official' SU damper oil and upgrade to K&N cone and carry on fiddling...

Cheers

Don't worry about 'SU Oil' - my car runs best on engine oil in the damper.

beware that K&N air filters are very noisy.
There are many reports of people taking them off because they can't stand the noise.
D