1966 Volvo 121

[quietside]

You probably know this car - I've had it a while.

It's a 121 manual, so:

DC generator
Unservoed disc/drum brakes
B18A engine (single carb, 'A' grind cam)
4 speed manual, no O/D.

I need someone to help me cure an infuriating fault it has - cutting out at junctions after runs at NSL.
No-one, and I mean *no-one*, can make it behave. This has been going on for the best part of seven years.

Let me go through what's been done/replaced:

Carburettor (Zenith fell to pieces, Scandcar Weber 34ICT fitted, don't give me shit about SU carbs, they won't solve the problem and I can't afford one or a pair of HS6s and the choke/throttle linkages, and I'm sick of hearing about fucking wonderful they supposedly are). Carburettor set to Weber factory numbers.

Dizzy (now 123 ignition)
Coil (now Aldon Flamethrower)

HT leads

Plugs (perfect deposits)
Valve clearances set
Fuel filters x 2

New mechanical fuel pump from Skandix. Was thinking of looking at a HUCO electronic piece.
Pump delivers book pressure.

It's set up for timing on/by the Volvo workshop manual - dwell, advance, the lot.

The engine cuts dead as you pull into a junction; pulling the choke out, heel toeing or clutch kicking brings it back to life.
If you miss all that it will crank up and run again first turn of the key until you get to another junction after an NSL run. It behaves immaculately at lower speeds and doesn't stall.

The fuel is clean and the filter to the carb is filling up. No fuel starvation. Everyone is insisting it's fuel starvation but the bowl and filter are full if you pull in and pop the bonnet when it cuts.

Starts instantly. Pulls like a train (it will pull hard up Rhuallt hill on the A55).
Always run on high test, tank cleaned five years ago.

Other suspects:

Shitty breather[s]
Exhaust back box has a broken baffle.
Generator/generator regulator a bit shagged, despite new drive belt fitted.

Any suggestions from sensible folk appreciated. I want to stick it on a rolling road and induce the failure but everyone else is saying that that's 'madness' and 'it's not a racing car', yet these same people can't tell me why it keeps shitting itself.

[panhard65]

That is an unusual and annoying fault. I think it is probably carb related and the rolling road idea is a very good one if you have access to one with someone who knows what they are doing. It should at least make it possible to recreate the fault and adjust things without having to keep running round the block. It could be a vacuum / breather problem, but you could end up with parts roulette without getting it on a rolling road. It does seem as all the usual suspects have been done and the webber if set correctly is far better than SU's but they are not easy to set correctly.

[quietside]

That is an unusual and annoying fault. I think it is probably carb related and the rolling road idea is a very good one if you have access to one with someone who knows what they are doing. It should at least make it possible to recreate the fault and adjust things without having to keep running round the block. It could be a vacuum / breather problem, but you could end up with parts roulette without getting it on a rolling road. It does seem as all the usual suspects have been done and the webber if set correctly is far better than SU's but they are not easy to set correctly.

It's steadily turned into a parts roulette affair. It cutting out on the road might get dangerous if whoever's following isn't paying attention.

North Wales isn't the greatest place for rolling roads; plenty of rally specialists but no-one really keen on looking at older stuff.
It's also an example of 'too many cooks'; so many people have had a go at it I'm at my wit's end now.

[Scruffy Bodger]

North Wales isn't the greatest place for rolling roads; plenty of rally specialists but no-one really keen on looking at older stuff.
It's also an example of 'too many cooks'; so many people have had a go at it I'm at my wit's end now.

That surprises me. There must be plenty of Mk2's running round still on carbs as they go to historic classes because they can't afford Millington Diamonds?
There was even an Amazon being run on the Woodpecker a few years back, got a photo somewhere.

Great looking car btw.

[quietside]

You answered it in one: it's not a Mk2, so do one. They're just not interested, unless the people I've spoken to are shits.

[captain_70s]

Wot u need is sum SUs m8

In all seriousness it has to be carb related I'd have thought. Sadly I only know SUs so am no help at all.

Lovely car though...

[quietside]

Two carbs from two different manufacturers showed exactly the same symptoms.

I'm not sure it's the carb.

I am deeply baffled by the cult-like following of SUs. I've run out of digits to represent the people who were adamant a pair of SU HS6s (as per a 122S) would 'absolutely' fix the problem, but were unable to tell me why.

So unwilling was I to drop £500+ on a pair of unknown quantity carburettors (plus choke/throttle linkages and misab) that I said I offered said bullshitters the chance to lend me a known working set up to me and I would fit them to my car; were said wonder carburettors shown to solve the problem, I'd give them the money for the setup as it stood.

They all declined.

SU people charge the earth for their wares; when I was skint, I sold off a later SU B20 set up with carb, misab, linkages and airbox.
They sold on eBay for £100 and the buyer still complained.

[LynehamHerc]

Given it happens when the airflow under the bonnet ceases and the engine's hot I'd guess it's fuel vapourisation.

[quietside]

Given it happens when the airflow under the bonnet ceases and the engine's hot I'd guess it's fuel vapourisation.

If it was vapour locking it wouldn't start up again straight away. I had considered an electric pump to keep feeding it cold fuel and CDC has one of those tiny temporary electric pumps you use to get barn stored cars going. I'd need a Malpassi to vary the pressure but it might be worth a go when I have a spare £100 or so.

As it is, you can literally fire it back up in neutral as it's still rolling to a stop and it'll burst into life again as if nothing has happened.

I'm not rubbishing your diagnosis, but it would flat out refuse to restart as easily as it does.
It cuts out regardless of ambient temperature.

[NorfolkNWeigh]

Could there be some sort of early safety related fuel flow cut off in the system ? I’m clutching at straws here but Volvo were the first with most safety bollocks. Have you tried bypassing the petrol line , pump etc? Either with a gravity fed system or an old electric pump, if it does it at every stop , one quick blast down a by-pass with a Jerry rigged set up would be enough.