IDS - IDA - IDT

ChrisF · Post by **ChrisF** » Mon Aug 16, 2004 9:24 am

Can anyone explain the detailed differences between these carbs as I need to replace some Solexes.

Lightweight_911 · Post by **Lightweight_911** » Mon Aug 16, 2004 10:24 am

You can use any of the 3 versions of Weber carburettor (with appropriate jetting) to replace your Solexes.

Porsche originally used the IDA's to replace the Solexes for the 'S' models in early 1966 (the Webers were used on several Italian cars including the Lancia Aurelia V6's).

IDT's were a modified version of the IDA used on the 'T' models & incorporated different jetting & idle mixture screws with a different taper.

IDS's were introduced for the 'S' models sometime during 1968 & incorporated an extra 'high speed enrichment' circuit - this apparently gave no increase in performance but was meant to be a safety feature to prevent destructive detonation at high revs.

Whichever version you fit you will need to ensure that the manifold internal diameter matches the inlet ports (so probably better to start with 'T' manifolds).

ChrisF · Post by **ChrisF** » Mon Aug 16, 2004 11:03 am

Thanks, very helpful.

We have a 2 litre engine that revs to about 8000rpm and we can't seem to get the bottom end right with Solexes.

Our Rolling Road tuner has suggested we try 28mm chokes in the Solexes but they don't seem very common.

Lightweight_911 · Post by **Lightweight_911** » Mon Aug 16, 2004 12:20 pm

You could try giving Jim Avis a call on 01293 851449.

He used to race a 1965 or 66 911 in FIA events & may be able to offer some suggestions.

Peter · Post by **Peter** » Mon Aug 16, 2004 1:42 pm

What is the benefit in fitting Webers (apart from replacing knackered carbs)? Is there any performance increase, easier tuning, reliability, etc?

I have Zeniths on my 2.4T and have wondered about whether a change might be worth considering.

Lightweight_911 · Post by **Lightweight_911** » Mon Aug 16, 2004 2:18 pm

The original reason that Webers were fitted was to eliminate the 'flat-spots' that plagued the Solex-fed cars.

When Porsche went over to using Zenith 40TIN carbs instead of Webers for the 2.2 911T models, it was essentially a cost-cutting exercise.

The advantage that Webers have over both the Solex & Zenith carbs is the much greater availability of alternative jets, chokes, emulsion tubes, etc.

pppgbr · Post by **pppgbr** » Fri Sep 24, 2004 10:40 am

Hello there.

I think this problem is almost universal with Solexes..

The spindles almost always leak air..I'm told even when new!

There is no advantage to smaller chokes...

Regards
David

willbrown · Post by **willbrown** » Fri Sep 24, 2004 1:19 pm

Peter, if you're feeling flush!

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 57227&rd=1

Lightweight_911 · Post by **Lightweight_911** » Fri Sep 24, 2004 5:53 pm

Will - I don't think those Webers would be much use to Peter as they're twin-choke IDA's for a 4-cylinder engine...

willbrown · Post by **willbrown** » Fri Sep 24, 2004 8:00 pm

Best not buy those then...don't think they'd fit.

I'll get my coat!

Post by **Bootsy** » Fri Sep 24, 2004 8:14 pm

Lightweight_911 wrote:Will - I don't think those Webers would be much use to Peter as they're twin-choke IDA's for a 4-cylinder engine...

Bit big for a Super 356 engine - now if they were 40s or 44s I could be tempted - I love 48 IDAs - lovely carbs

Graham · Post by **Graham** » Fri Sep 24, 2004 10:12 pm

I have four of those!!! One day they will adorn a big block V8 in a '27 Fad T hot rod........................

kenikh · Post by **kenikh** » Wed Apr 16, 2008 11:08 pm

To chip in a bit I'll paint with a very wide brush: Solexes are better carbs than Webers when set up correctly.

Why? Numerous reasons. Solex throats line up directly with the ports on a 911 engine. They have more tuning flexibility than Webers. Most interestingly, the flat spot problem is easily mitigated by a knowledable rebuilder like Duel or Harry Bieker.

I have talked to several folks racing their '65s w/ Solexes and all insist that the Solexes make more power. Think about it; with the more direct route for air, remote float bowls that keep the fuel from boiling in the carbs, no starvation problems from hard cornering, they are the carb of choice.

In talking to Harry Bieker, he insists that the flat spot issue was the result of a design flaw that caused the throttle shafts to wear quickly and improperly on these cars. He has rebushed hundreds of sets of these carbs and not only does this cure the issue, he has seen only a handful come back to readdress the issue. As far as the jetting problem goes, he reams the Solexes to accept 356 Solex parts, which removes the scarcity of parts issue.

Needless to say, I am hoping my set will be back from Harry very soon so I too can experience Solexes in all of their glory in my '65. I'll keep you posted.

Lightweight_911 · Post by **Lightweight_911** » Thu Apr 17, 2008 11:22 pm

On a side note, I've had a couple of sets of Webers refurbished by Bieker Engineering & they did a superb job.