Porsche 911. Pair of Weber IDA3C in for CO (Comprehensive Overhaul). Exterior condition before and after can be compared. However this service concentrates on operational efficiency and ensuring internal condition is as good as possible:- a thorough ultrasonic clean and rinse and after various internal checks, a very careful rebuild including accurate float levels and balanced pump outputs.
After a CO. A pair of these carburettors is a time consuming piece of work. Every care is taken to ensure that all parts are dismantled without damage - spares can be a headache. However, the biggest problem with these carburettors is throttle shaft wear- this needs to be resolved as soon as wear is identified and before the bores get marked and damaged by the butterflies. JRS is currently developing a series of restoration services based on the original Weber concept of oversized throttle shafts. With the appropriate machining services this will resolve body wear, spindle wear and bore wear problems. Most current repair offerings fail to address throttle shaft wear!!
Rebuilt with new gaskets, pump diaphrams and float valve assemblies. Rebuild kits are expensive and some are very poor in that many essential O rings and copper washers are missing and fuel filters are usually of the wrong sort . These missing components have to be obtained if the piece of work is to be completed properly.
Throttle shaft problems have been referred to earlier in this series of pics. These are later 40mm IDA's and shaft wear is just beginning to be apparent. Generally, 40's wear better than the larger carburettor sizes: Earlier metal bushed carburettors wear better than later ones, but the shafts wear. Later PTFE bushed carburettors last less well, but shafts tend to wear better.Pump calibration is crucially important and so is the ACCURATE setting of the float heights across ALL FOUR floats. Best done with the carburettors off the engine and on the bench. How many "specialists" do it? The number of damaged floats I have seen suggest that a grope in the dark corners of the engine bay is favoured by many Porsche "technicians"!!
Wear in the throttle shaft bearings allows air to enter. It also allows the butterflies to damage the bore of the carburettor. Lapping these bores can remove minor damage. Oversize butterflies are then required.The JRS throttle shaft development programme is based on the original Weber "remedy" for wear:- the fitting of oversized throttle shafts. Why? because this is the only way in which wear in the inner bearing surfaces can be remedied. Currently most "repair" options involve bushing/rebushing the outer bearings only and wear elsewhere is ignored. Note that there is a limit to the amount of bore damage that can be recovered before idle and progression phases of carburation are compromised.
Accelerator pump castings distort, allowing fuel to escape and pumps to operate at less than recommended volumes. The remedy: machine the pump covers and accurately recalibrate the pumps.
The last pic of this IDA series. A substantial amount of rust and fuel residues were removed from the float bowls and passageways in this set of IDA's. Jets were also heavily contaminated and again throroughly cleaned. This is probably the first time this set of Webers has been PROPERLY overhauled. As well as the contamination, all float heights differed significantly and none accorded to the Weber specification, one float was butchered, pumps leaked, pump calibration was wrong, pump build was wrong on one unit and washers, security wires were missing. All of that is now resolved!! A bonus is the external appearance has improved. Porsche IDA service doesn't get much better than this. The completed work is returned to customers via insured carrier and a letter detailing the work completed accompanies the carburettors. JRS: an engineering approach to carburettor cleaning and restoration.
Another pair and another story. Soaked in release fluids for a couple of days, this mess came out of one of the instruments. This is the result of internal corrossion of the alloy body. Its extent.......?
Drain screw. Sealed with Araldite? No, Araldite is holding the severed head on. Wonder who did that?
More of the same.
So what else?
Looks normal - ish
and here.
Top off and the usual float damage on LHS. Who does this?
Floats OK here.
Everything left in the body is seized including the Araldited drain screws
Same here.
This air screw is seized.....
...and so are these two....
..and so is this shaft. Sent to JRS for overhaul, this set of carburettors is full of potential pitfalls. Given that the extent of internal corossion cannot be ascertained the question as to whether overhaul together with its costs is warranted is questionable. Asked by my customer, I said NO so they will be returned. JRS - can be relied upon for unbiased, honest assessment. HOWEVER .. somebody else said they could do the work so over to them. I hope to find out what (if anything) was done and what it cost!!
