Hi Eddie

I've just started reading your thread v intersting too. I'm not interested in modding my SV 1725 so will keep the twin strombergs but have a question.

I've always put 20/50 engine in the dashpots is this stupid?

2 Things to say, Thanks to Sunbeamowner for replying to the previous post but how the hell does a non-member get onto our forum ? That might be something that needs attention.

A further development to my thoughts on idle jet size. I had a reasonably long run down to John Timms at Contract Paint. ( He's rebuilding my Hardtop, and it was possibly the worst basket case he's ever seen. Needless to say it will probably be the last one he ever does as it is such a pig of a job and getting it to fit required my car to be there )

The 0.65 jet is 96% perfect but for me that isn't good enough. Occasionally there will still be a trace of hesitation at certain moments after throttling back and then coming off the throttle stop. I think I will get the 0.70 to see if this will finally be the answer.

Apart from this slight hiccup the performance is simply amazing. The engine is so creamy smooth whilst cruising it feels unbreakable. Hard to believe a carburettor change can make such an awesome difference but then this is no ordinary carburettor is it ? When I bring my car back from JT's it will be on a 0.70 idle jet so I will report back on this.

Regards Eddie

I think Chris is more knowledgeable than me about the correct oil in the Stromberg's dashpot. I believe there is a purpose made oil available from Southern Carburettors. I would imagine 20/50 to be a bit too heavy but I stand to be corrected if wrong.
Regards Eddie.

I've always put 20/50 engine in the dashpots is this stupid?[/quote]

From the days when I owned SU carb. cars, Morris Minors (convertibles of course), Sprites etc the perceived wisdom was that a 'light machine oil' should be used, for example 3 in One. Anything heavier over-damped the piston and thus adversely throttle response.
But don't take this as gospel - wait for a more expert view.

Hi Edddie and everybody else.
Have now fitted the Weber 32/36 DGV to my prototype Series 111 automatic, having knackered an exhaust valve seat on the cannes trip, and had the head rebuilt by Headshop, Warrington.
Also fitted the K&N Apollo air filter system. It frightened me to death going to Alpine committee meeting- doing just under 75 on M6, had to accelerate to avoid a problem, when the most appalling rattle came from engine. oh excreta, sounds like bearings!!! Slowed down to 75, noise went away- it was the jubilee clip on intake plenum hitting the bonnet underside, and extra torque reaction caused it to touch the bonnet stiffener.
Had a good look at it, and have cut the snout off the plenum at 10 degrees, and welded it back on upside down, giving an extra 10mm clearance.
The performance is excellent, sits at a steady 70mph on motorway with no fuss. on the trip to Cannes with the old 28/36, acheived 27.4 mpg, good for an auto. The trip to Westcott and back, over 300 miles, acheived 33 mpg.
HOWEVER!!!! there is still the problem of transition from idle to low speed.
I now know that the vacuum advance works properly, it was slow because the bit of spring steel which holds the plate down was too tight, and the unit would not move properly.
It still falters on pickup, but not all the time. I have the volume screw well open, probably 3 turns, which sounds a lot. When going into a roundabout on trailing throttle, the engine can cut out, -upsetting!!!!
It seems particularly bad when going quickly downhill-I live on the way down from the Cat and Fiddle road in Macclesfield, so there is potential for fun- the pickup seems better uphill rather than down, a difficult thing to assess on the driveway.
The carb arrived with a 55 jet in primary and a 50 in secondary. I now have a 65 in primary, but still the 50 in secondary. Is there a need to alter the primary idle jet?
Also, when I still had the 28/36 fitted, idle was not good, and using a colourtune was educational. No 1 was not fiting until I opened up the volume control needle, so I will try the colurtune again to see if it shows the same problem.
Also could the ram air effect be contibuting to the problem?
At high speed with the throttle well open, things are fine, but at high speed with it shut, does this make the carb too lean?

Hi Graham, glad to hear that the car is performing reasonably well. It seems that you like me and everyone else is experiencing the same falter/ hesitation.

I have now got hold of a 0.70 idle jet from S.C.
Speaking to Steve at S.C. about this he explained how the larger jet in the idle circuit works. What happens is that as the engine draws in air the mixture at tickover AND the initial throttle opening is all handled by the idle circuit alone. At a certain rev band ( determined by the amount of air being induced thus producing a vacuum ) the primary circuit will take over. With the smaller size idle jets this rev band will fall short of the primary circuit cutting in. Hence there is the falter or flat spot. On the Mexico this doesn't happen so it is definitely a Rootes application problem.

The larger sizes will take the idle circuit to a higher rev band hopefully overlapping so there is a seamless transition. The 0.65 is almost there so hopefully the 0.70 will do the trick. If not we will have to look at the pump jet. A visit to Webcon UK which is close to me should provide some better ideas of where to go to fix this hiccup. I will fix this I assure everyone.
Thanks for your detailed post Graham it all helps to track the problem down. The end result should be well worth this slight setback.
Also it should be noted that when you change an idle jet for a larger size I found that I had to UNSCREW the volume control to smooth the tickover out, exactly as you say. Not sure why this is but maybe Webcon may know. End result is even more poke than before so maybe not a bad thing.
I haven't tried my gas analyser or ColourTune yet though.I'll let you know how the 0.70 pans out. The Yanks say it is spot on. We'll see.
Best Regards Eddie.

Found on Ebay.....any comments ?

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Well, it seems I have got 3 posts to reply to, so here goes.....................
Dusty, you're experience with the choke perfectly mirrors mine. Yes, FULL choke is required and a couple of blips of the throttle pedal to sqiurt some go juice into the manifold is a good idea to. She will fire instantly whereupon I find the engine will run well at fast idle with the choke out about half an inch or a tad more if it is really cold out. Sometimes she will falter for a few seconds but mostly you can drive straight away, leaving the choke out perhaps a quarter of an inch on the fast idle cam. Obviously the size of the idle jet affects this behaviour and as you go to the larger sizes it gets more maneageable as you'd expect. So keep at it with the 0.65 and 0.70. you'll get there I'm sure.

Mackem, replace your 2ndary idle jet with the original size, you should not change this as it has nothing to do with the progression circuit which is what we are dealing with. If you still have the 0.55 in the primary barrel (which is the one that opens first ) then this will explain your cold running and other faults. My experiences point to the main primary idle jet needing to be 0.70, although many people would probably be happy with 0.65 and slightly better economy. With the Holbay I would definitely be wanting a 0.70 idle jet in the primary progression circuit.

Sunbeamowner, yipes that is some manifold there but before you all rush out trying to get one there is bad news. The carbs are placed round the wrong way, they are facing the cylinder head. Twin Choke downdraft Webers need to face forwards in order for the floatchamber design to work properly. Also the throttle linkage will be an absolute nightmare to get to work at all let alone be synchronised, and I'd bet all the tea in China that a suitably equipped ( ie. NZ manifolded ) Alpine with 1 32/36 would leave it for dead, but interesting all the same. Well spotted.

Hope that answers everybody, boy, is it busy on the Forum tonight !
Regards Eddie

Further to the problems I mentioned earlier, consider the fuel distribution between the 4 runners, remembering that the whole point of twin chokes is their superior progressive qualities. At full bore cylinders 1 and 3 are going to be running extremely well supplied whilst 2 and 4 are going to be poorly supplied, hardly much good for racing. Another good idea bites the dust. Steer well clear of this sort of thing no matter how powerful it looks.

Also the reason right angles in manifolds is bad news is that the atomised fuel droplets tend to overshoot the corners and soak the manifold walls in neat petrol which is why the standard manifold runs 1 and 4 excessively rich whilst 2 and 3 are OK. This is why Log manifolds are such poor performers. There is much more to good manifold design than meets the eye.

Best Regards Eddie

Hello Eddie,

I have followed your threads regarding the DGV carb, and have tried hard to get hold of a set of throttle actuating rods for my Strombergs for a SeriesV 1725 (re- wanted thread) to no avail.

I am now looking into the 32/36 DGV carb and have one that came from a 'F'ix 'O'r 'R'epair 'D'aily (a four letter F word) that is in vary good order.
The same situation applies with the Jetting as in previous mails to your thread and I will sort them out if you can help me with a problemette.
My cab has 32/36 DGV FA stamped on to the body and as mentioned all jets, em tubes are the same but the primary idle jet will need to uprated to .70. BUT seeing as the carb has the suffix 'FA' it does not have a tube to the primary venturi to allow for the vacuum advance/retard suction on the dizzy.
Can I drill into the carb body base and try and fabricate something (Is there a special size for the brass tube bore?), or would I be better off replacing the dizzy for the 23D4 type as in the H120 engine that has no adv/ret vacuum but a mechanical auto advance mechanism that cuts in at 500rpm (my 25D4 type is a bit suspect anyway and will be replaced)

Thanks

Aye Grumpy, that it does.
Paul, the vacuum advance retard really comes into play on the overrun.ie. when you throttle back and the engine is still at high revs, without the vacuum pipe you're going to be backfiring, hiccuping all over the place, and getting a poor tickover to boot. Also the low speed pickup will be compromised.
Unless you have a Holbay you really need that vacuum circuit. You can't just change distributors on a whim. It is far too important an item, possibly the most important item apart from the engine under the bonnet.
If your dizzy is knackered get it rebuilt by the Martin the Distributor Doctor to as new Series V calibration. Although the carb you have may work with a suitable brass pipe inserted, it just as likely may not.

You all already know what I think about 2nd hand carbs so I won't bore you all with it again but the cost of a new one is incredibly cheap at the moment ( List Price is £275 plus Vat from Webcon ) £ 159 post free from my favoured supplier. How long this will last is anyone's guess but it may not be much longer. It really is a steal. By all means experiment but don't lose the plot or you'll get into the smelly stuff.

Regards Eddie