'NNN' and the overheat saga

[morris_carl]

It's the most easy engine to get apart, took me 25 mins with a tea break !

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[mickthefitter]

It's the most easy engine to get apart, took me 25 mins with a tea break !

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Yeah yeah yeah....I've heard stories like that....people who decorate their houses top to bottom in a week...

[david painter]

For what its worth now I would refit the rad now you have backed the choke off and see how it goes then move on from there. As for taking the engine to pieces in 25 mins bit super human in my opinion but wont be able to put back together that quick!!!
Dave

[mickthefitter]

Progress update, Stardate 1st September 2016 at nearly half past two in the afternoon...

The new radiator is back in. I've filled it with plain water in case it wasn't successful and I'd then got to move on to Halfords flushing solutions, so that I didn't waste any Blucol.

I've not long got back from a reasonably lengthy drive. I've endured shoppers, early home-timers, large wobbly cyclists in bright pink T shirts, Highways Maintenance pick-up trucks pulling out on me, being stuck behind large tractors pulling trailers, said large tractors passing parked cars with me following through because surely the Honda Civic and Vauxhall Astra coming the other way will give way....said Honda Civic mounting the pavement because the dozy twonk behind the wheel thought he was going to take on a big tractor and trailer - which left me in a nearly stalling automatic Morris Marina with heavy steering having to heave over to give him room to squeeze past....added to which at any time I thought my car might expire or decide to turn into an erupting steam engine. But it didn't.

Radiator...success! I even coaxed the thing to nearly sixty miles an hour but it was like pulling teeth. The temperature needle had a little dance just either side of the halfway mark depending on how hard she was working, but I'd say, no way does my cylinder head need to come off to clear the waterways. There might be other reasons though....

So when its cooled down, I'll drop the water out and refill with 33% Blucol. And call that job concluded. Then there's the other stuff.

Since I've altered settings on the distributor and now the choke cable on the carburettor compared to how the car came to me, its a pig to start from cold, doing the Flight Of The Phoenix cough-splutter-chug-chug-stall thing, when I finally got it running (choke in, choke out, choke halfway, dance on the accelerator pedal, keep some revs up till its warmed up) and out on the road it wouldn't pull the skin off a rice pudding. Trying to get to 50 or 60 feels like you're pulling a house. She's always seemed to have a bit of a lumpy tickover, although KRB 158P was never silky smooth, and back in the day someone said to me (or my stepfather, as it served as the family car) "your big ends are knocking" as KRB seemed to go 'clank-clank-clank' a bit at idle. Never did it any harm and it never changed.

I also keep smelling petrol. I've already changed a weepy float chamber lid gasket on the front carb, as according to Mr. Tinkerer's notes he'd blown out a bit of muck that was causing the float to flood, but evidently the gasket was past it's best but replacing that with a new one was beyond him. But just having pulled onto my drive after my run out, sniffing around, the petrol smell now seems to come from the rear carb, but to me that looks completely dry.

Can anyone tell me about petrol smells on SUs and the reasons?

[JubileeNut]

Float chambers can seep a bit now and again but should not do it all the time as this may show incorrect float setting or poor jet in float chamber.
Twin SU carbs should be a bit lumpy on tick over and go smooth as soon as throtle applied.

[mickthefitter]

I just put my last new gasket on the lid on the back SU, to be on the safe side. I don't think the old one was leaking and the new one hasn't changed anything. I'm not sure now if its simply the draught from the fan blows smells away from carb no.1, but carb no.2 is shielded by the air filter body so I can smell it a bit. Maybe, as I strongly suspect, my carbs are so far out of wack that it has something to do with excessive petrol smell. At least the tickover bit sounds right then! There's definitely a marked hesitation when applying throttle - when the car is cold and idling it just stutters and then eventually the revs catch up.

[david painter]

With properly set up twin SU there is no reason engine should be lumpy at idle. Does depend on rest of engine being in good condition ie compressions equal good valve seating and tappets set correctly well at least my MG isn't lumpy at idle.
Dave.

[mickthefitter]

Gil's matt blue Mk2 1.3 had one of the sweetest sounding engines I've ever heard when I saw it at Quorn.

[JubileeNut]

Well I was told from a very good source about lumpy at tick over. I am not talking bad by any means but mine has always been very slightly lumpy and my engine and carbs are as new as you can get.
They have been properly set up with air flow meters and colour tune (2 sets one on number 1 cylinder and the other on number 4). Get the very slight rise in revs when the dash pot pin is lifted etc etc.
Car runs very well and pulls like a train.

It gets lumpier when the fuel evapourates but that is not the sort of lumpy I mean.

There should be no hesitation at all though.

[morris_carl]

Glad you got the temperature under control ! I'm sticking with my theory the rad was good enough to cool it 30 years ago so should be no reason it shouldn't now haha,

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[Kilroy]

Mick

In all my experience, timing made far more difference than fine tuning the carbs.

I suspect you should try advancing the ignition slightly just for comparison..

[MarinaCoupe]

I agree with Kilroy, if you are struggling to get to 60 then something is off.

Your recollection about the performance of previous Marinas is based on a well set up car and leaded fuel. By the sound of what you found on this one the last owner didn't know what they were doing.

Always set the timing first (vacuum advance disconnected) and lock it down, before adjusting the carb(s).

Keep going, you are making progress.



Time to reset the timing


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[mickthefitter]

I've just seen something while trying to set the timing on 'NNN' that I think might not be right, and if it ISN'T right, it might go a long way towards explaining the poor performance.

As on previous occasions, to time the car, I've disconnected the vacuum advance pipe, plugged it, set the engine revs to 1000rpm, and I chose to set the crank pulley mark to 10 deg BTDC again, by the book - not recommended maybe for unleaded petrol, but I thought I'd start by the book and go from there.

Then I decided to look at something I'd not looked at before, checking the function of the advance mechanisms.

Going by the leaflet in my old Gunsons timing light kit, first I tried increasing the revs with the vac pipe still off: holding the timing light in the right place and trying to reach under the air filter to pull on the throttle linkage without getting burnt is not the easiest trick to pull off - also with mine being an automatic, that kickdown cable adds a lot of drag to manually trying to manipulate the throttle under the bonnet. I wasn't very progressive, and I don't know what the revs were as I couldn't see the tacho - I've also got neighbours out in gardens and I wasn't going to test the limit of the mechanical advance by going up to around 5000rpm either, as suggested in the Gunsons leaflet. But I saw the timing mark move towards the advanced side with increased revs so satisfied myself at that.

Then I put the vacuum pipe back. As expected the engine revs went up. I didn't bother to notice by how much, but it was a fair bit. Maybe up by 500rpm. So I tweaked the carbs back down to 1000rpm and shone my timing light on the pulley before expecting to raise the engine revs again to see the timing mark move. Gunsons said something about the vacuum advance beginning to work around 1000rpm, which was the speed I was idling at, but actually that isn't a bad speed for an auto as the torque converter drags it down a lot in gear.

What I THINK the problem is, unless I'm told otherwise, is that when I shone my timing light at the pulley at 1000rpm with the vacuum pipe on, the timing mark was WAY, WAY over to the offside of the car, on the advance timing side, miles clear of the timing marks.

That cannot be right can it? Is this why the car is spluttering and struggling? I will state my position here and now that I have never dismantled THIS or any other distributor in my life - the inner workings of that are only known to be from diagrams in manuals, and in the past my attitude has been if it ain't broke, don't fix it.

Aside from that - I've said the engine idle is a bit lumpy. More appropriate would perhaps be that it hunts slightly. I know one theoretical reason for that could be air leaks. Is it also a symptom of out of balance carbs?

Don't know whether to touch the carbs now till I get a reply on the dizzy!

[mickthefitter]

I've just read in the leaflet, if the vacuum advance in working at idle, it could be due to imbalance in twin carburettors...I'm putting the kettle on then going back out there with my new toy (Carbalancer)

I've just put a Gunsons Autoranger in the bin. That bloody thing has never been any use. It didn't seem to be giving the right dwell readings when I tried to use it to set points a few weeks ago, and today the rev counter was intermittent. Dodgy rotary range change switch. I got it working long enough to prove my Marina's tacho is accurate, but then I tried to open the case to look at the faulty switch, which of course was part bonded shut, and broke it. No great loss.

[aqua-marina]

It sounds as you are struggling with all the pieces of equipment and paperwork around you
Sometimes you can read too much
You have to remember these are basic easy adjustments even without timing light or carb balancer
I would start with the carbs
Get the jets even start car go up or down a couple of flats til revs peak
Make sure throttles open at the same time back them right off and turn them the same amount till the car is at idle
As for the timing as a good guide engine running vacuum on leave distributor clamp loose enough to turn distribution with engine running turn till revs go up if you go past this point back off till revs even out
Lock clamp up and give car a run
With these basic adjustments car should pull better than you have experienced
Good luck whole job less than a hour