V12 Strombergs

[Beardspeed]

Hello to everyone. I am not a keen do-it-yourself person any more, as most things I now attempt seem to turn to the proverbial! This is also my first post so please be gentle

Purchased my 1971 V12 2+2 April 2014 and visited my local Jag (specialist) shortly after. Problems of starting when hot and erratic tick-over two of the items I listed for checking.
New metering needle valves and diaphragms fitted to all four carbs. and with other work, car ran much better, tick-over set about 500 rpm. However, tick-over very low after +1 hour run.
Next problem an off-side carb flooding and revs sticking at whatever throttle opening applied!
New needle valves, seats and floats fitted to above 2 carbs. and off I went again.
Some time later one of the near-side carbs flooded so valves, seats, etc., replaced on these two.
Unfortunately, the revs are still not falling off quickly enough for me when you blip the throttle, despite all linkages appearing to return to their idle position, and thinking a higher tick-over setting?
Anyone experienced similar problems and resolved, or any suggestions please?

[oldtimer]

Hi,
The problems you refer to are not uncommon! Yes I've had all of those over last forty years

V 12's on carbs get very grumpy if they are left in the corner to sulk.

They need regular exercise to keep every thing in good working order.

You may care to tell us a little about the car itself and your knowledge of such things.

A book could be written to cover the broad brush items you have listed and therefore hesitate to make any suggestions at this stage. Many of us have spent a lot of time sorting these little problems and in doing so have gained a good understanding of the various idiosyincracys rained down upon us.

You have mentioned that you visited a Jaguar Specialist, I have never had the opportunity to use the services of one of these but from this BB it appears they come in various shapes and sizes.
One needs to take into account that the Stromberg carb probably went out of production before some of the young men in the trade were born so it is not a component that they are well versed with.

From your description the cost in terms of parts could be minimal but the time to go through the various elements in a systematic fashion could be significant.

I'm sure there are numerous folks who will guide you through stage by stage but not a scatter gun approach covering every thing in one go.

Sorry if this does not, in the first instant, answer your question but given time I'm sure some progress can be made

Oldtimer

[Beardspeed]

Dear Oldtimer

From one to another thanks for reading my query.

The car has covered approx. 2000 miles with me and now has a genuine 44,000 on the clock.

My Jag man runs his own garage and looked after my old XJ40 some years ago. There is often at least 2 E types in there with XK 120's and 140's, plus most other Jag models from 1960's through to servicing my 2010 XF. Latest conversation with him on the carb. problem he mentioned a possible leak on the vacuum connection, when I can next get the car in.

I put the subject out to the Forum a) to support it and b) to contribute my (your) input to the problem(s) when in the garage.

So any suggestions greatly received.

[oldtimer]

Hi,
I have read your reply which trough's a little more light on the subject.

Bit late for me tonight so will try tomorrow

Oldtimer

[raysearles]

This happens all the time on my 71 V12 2+2, even after a load of work and balancing everything professionally through a exerienced mechanic.

Bottom line, she runs fine, and the last 12 years I stopped worrying about it. Nature of the beast.

[oldtimer]

I think Ray ,above pretty well weighs up the situation in one line.

I think one develops a nack for starting them. Starting from cold is never a problem using full choke and pushing it half way in as soon as it starts. Even so, leaving it running whilst closing the garage doors can be problematic in that it can choke its self to death by over fuelling. Then restarting can be a real problem. In my experience, pushing the throttle full open and crank it, normally gets it going.

Much the same for hot starts, clearly some fuel expansion has taken place allowing it to flood the intake track, so once again full throttle and hope.

On the occasions that the engine has to be cranked over rather more than usual it gives the Battery a bit of a bashing. So obviously a good battery needs to be in place . I have an Accumate Battery charger permanently connected.

It may be worth obtaining a Service manual which would give a guide to the engine set up and controls.

Do keep in touch with your progress and let us know how things develop

Oldtimer

[raysearles]

Wise words indeed, oldtimer

[Beardspeed]

Finally I have managed to get around to an update on my problems with the Strombergs!

The main problem of the revs not returning to tick over was resolved with replacement of the vacuum unit on the distributer.

The other problem with erratic tick over (sometimes down to just a few revs) I appear to have resolved myself by reverting back to the lower octane petrol, rather than the "super".

With a little bit more tweaking by my garage man and a degree of being more familiar with starting protocol, cold and hot, can now report much happier motoring.

Thank you all for your input.

[J44EAG]

Two things i experienced with an 82 model facelift Stroberg carbed V8 Rover which had the power sapping US emission gear fitted.

The butterfly plates fitted to the spindles had emission control poppet valves installed. The theory being that going downhill with throttle closed would vacuum suck the spring loaded poppet open and lean off the fuel mixture. As these slam shut poppets wore into the butterfly plates, they would wear away the butterfly where they touched and then cause air leaks. The result was the car would hang onto its revs during normal driving. My solution was to dismantle the poppet spring and spindle and silver solder the blasted things shut! That cured that problem. If your Strombergs have those small poppets fitted to the butterfly plates, you might perhaps have the same issue that I had.

Secondly, the crankcase breather tube off one of the rocker boxes fed via a plastic Y-piece and siamesed to two pipes which led to the carbs. The Y piece would embrittle and fall to pieces. This also upset running so i replaced that Y piece. The running improved. Then I discovered that the two tubes leading off the Y piece where blocked solid with crank case breather residue. I cleaned those pipes out AND the two pipes on the carbs onto which those tubes were fitted. The pipes into the carbs were fitted on the inlet manifold side of the butterfly. Again those carb breather pipes where choked solid. I rogered those out with a 10mm or so wide flat screw driver and them that wonderful V8 came back on line properly.

I`m not an expert on a carbed V12 so can`t say one way or the other whether a similar parts fitting is evident on your car. I just offer these words in case they might be useful.

Mike K

[oldtimer]

Hi, Not sure where to start.
Lets start with Mike K suggestions. The crank case breather arrangement is much the same in that the breathing is to four carbs instead of just two. All the metal pipes in that breathing system are joined together with short lengths of rubber pipe and are just push fit with no securing clips. All the pipe work is securely clipped in position so the chance of any thing falling apart is remote. The rubber tube connecting to each carb seems to get some oil contamination which could contribute to a loose fit and air leak. Additionally there is always the possibility of foam white sludge build up in the pipe work similar to that which used to build up in A series engines if you remember that far back ! I have to say I have not experienced this.

From as early as the Mk 2 a lot of effort or jiggery pockery went on trying to meet the Californian exhaust emission rules. The purpose of fitting Stromberg's instead of SU's was an attempt to improve things. I believe the valves in the throttle butterfly valves to which Mike refers came in rather later. Next time you have the dash pots off you can check that.

I know it is getting late for me - past my bedtime -but I am sure the idle RPM should be 750.
From my experience a change of fuel grade has never made any difference.

The vacuum advance/retard has never been connected on my model year car ! I am sure that applied to Mini's of that period as well but would need to check

Oldtimer