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Hi all. I have a 74 spider with twin webber 40 DCOE on a factory manifold. Recently had them rebuilt with new rubbers, 123 ignition and jets. Just can't get happy with the performance, seems to lean out or run out of fuel at high rev (5000 or more) and seems to have flat spots in acceleration. Have an appt to have them retuned by Group2 in seattle next week. Am wondering if fuel pump could be an issue.

Car was off road for 7 yrs undergoing restoration. Original fuel tank was shot so replaced with later model tank which uses in-tank fuel pump/filter. At present that is the only pump running fuel to the carbs. Didn't the later S2 spiders use both an internal AND external pump? Could it be that running only the one pump is insufficient fuel supply when the engine is under stress?

Any thoughts or opinions appreciated.
 

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Later Spica cars did have two fuel pumps as did the Bosch injected cars. But, the fuel supply requirements are quite different for these cars than for one with carburettors. I suggest measuring fuel pressure and volume to determine whether you have a supply problem. The fuel pressure on my Sprint is regulated to 3 PSI and volume is about 20 GPH. The same pressure and a similar volume should work for a stock or near stock 2L. I think you are on the right track... confirm your fuel supply and other tune up parameters are within specs and then look at the Webers. Any particular reason you installed new jets in the carbs?
 

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Discussion Starter #3
Turned it over to the mechanic who installed the 123 VA ignition. I don't know a lot about webbers, especially two at once, so went along. Overall the car drives well, but a little frustrating when I want that little extra oomph that it used to have and that my spica 74 still does.
 

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1. First advice is that "Webers" has only one "b".

;)

In-tank fuel pump is waaay too much pressure for the Webers. These carbs like 3.5 to 4 psi; more just blows fuel by the float needle valve. Simple solid state pump works fine. Hard race engines like the higher output of a Bendix-type pump, often in a dual-pump configuration like the GTA. These mount in front of the rear axle normally. Need 40 gph for most engines, up to 100 gph for the race configuration. You MUST use a pressure regulator.

2. Fuel pump is likely NOT your problem. Webers are touchy to advance curve and jetting. Sounds like you have problems with transition from idle (actually low-speed) jets to the main jets, and perhaps mains are too lean. Getting the jets right is not trivial - there are a lot of variables. Search the BB for weber jetting for some advice, but you'll likely need to find a good weber expert to get it right.

Robert
 

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I hate to say it but I had similar problems when I rebuilt the Webers on my '89 33 Cloverleaf Sportwagon, many years ago. I eventually found a great guy who worked from under the arches of a railway bridge in Glasgow and had been trained by Alfa Romeo in Milan as a young man and had many years of twin carb Weber experience. He spent about 30 mins with a long handled screwdriver handle pressed against his ear while he adjusted my carbs. All I can say is it was like driving a new car after that!

His advice otherwise was to give the car an "italian Tune Up" whenever it didnt feel right after that.

"an Italian tune up?" said I.

"yeah. Try and reach the redline in every gear! Its an Alfa engine. You cant break it before the bodywork falls of the car. And it expects to be treated badly"!

The only problem with this advice was that this car had the worst brakes on any car I have ever owned! So be warned! Make sure you can stop from 120mph before you get there :)
 

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"Italian tune up" is an old Ferarri notion. The point is that the facrtory put very cold plugs in the alfas - Lodge H2's. They would foul with dark black soot without even starting the car. But driving around town and especially up hills in low gears at near max rpm, the carbon deposits would burn off, and the car would run really well.

Till the plugs fouled again.

Rinse, repeat.

Alfas have always liked to run in that broad red zone on the Tach. Never seen any harm, unless you miss a gear, pop over 9,000 rpm, and bend a valve.

Then total catastrophe. A bit like kissing Sophia Loren. really sweet, then Blam!

Very Italian.

Robert
 
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