Fiat 124 Weber 38 DGES

TVST*R · Post by **TVST*R** » October 17th, 2007, 5:58 am

My engine is a stock 1800 with Mark Allison's Python Header and exhaust.
With this Weber installed, I am getting a pretty severe flat spot at around 1500-2000 rpms off the line. Otherwise, pulls very strong and wayyyyy better than my old 32/36 (for sale).

Any ideas as how to fix this?
Thanks!
Tom

Post by **Guy Croft** » October 17th, 2007, 10:13 am

Sorry, but that carb is a hopeless choice. I have read more 'guff' about it being suitable for every car from 1200cc up than any other carb. It's not, and for what it's worth the only engine I would ever use it on is a 3 liter Vee engine - where each barrel feeds a separate bank - or something like that.

Assuming the header is not way too short the flat spot on pickup is almost certainly due the synchronous operation of the throttles. Meaning they open together at the same time and so the airspeed drops too much on small throttle openings to give a good fuelling signal (insufficient depression).

Change it to a carb with 'progressive chokes' (well, actually it's the throttle plates that are progressive but no-one calls them 'progressive throttle carbs'..) and the 32/36 DGV series with electric choke (oh dear - cold start device..) DGEV, water fed auto DGAV or manual DGV. That carb has 8% bigger choke area than than the OE carb and will give you the best power and torque you'll ever get from a TC on a single carb setup.

GC

TVST*R · Post by **TVST*R** » October 17th, 2007, 4:57 pm

Other than that flat spot all is fine and it pulls wayyy better than the
32/36 beyond 3000rpm. I also have a K&N filter on it.

Why would you consider it a "hopeless" carb? What can I do to improve the airspeed for this setup?

T

Post by **Guy Croft** » October 17th, 2007, 5:06 pm

I don't want to sound 'clever' about this, but you're not the first that has reported this effect with that carb. Let me turn it around. A great carb would be one that bolted on and produced everything you wanted!

A flat spot like that may be 'liveable-with' (being who I am it would never be so for me) and sure you can drive through it but the effect it can have on rings and bores due to adverse fuelling can be quite serious. And I figure that you would not have mentioned it if you did not feel it was significant yourself.

I don't think you will get rid of the flat spot.

GC

TVST*R · Post by **TVST*R** » October 17th, 2007, 5:41 pm

You are correct Sir!

Must get with my Master Mechanic on this one...:))

HFStuart · Post by **HFStuart** » October 24th, 2007, 7:41 pm

Guy,

With apologies for my being lazy, does the 32/36 DGV have the same bolt fixing pattern as the DMTR / DATR fitted to lots of Betas ? ie will it go on the same manifold ?

Thanks

Stuart

Post by **Guy Croft** » October 25th, 2007, 2:32 pm

Yes it does, but just talking a moment ago to the helpful Andy Gray at Webcon UK about this on your behalf the DGV carb is not suitable for transverse operation due to the layout of the float. Like the problems you can get putting DCNF in a RWD application you are as likely as not to get fuel surge on corners. So my advice is avoid it.

Whilst the 32/36 DGV (26/27 chokes) series is a great performance upgrade on the, say 2 liter RWD Fiat TC compared with the standard 34ADF (24 chokes), there was never such a carb made that would bolt straight on to the transverse (FWD) Lancias originally fitted with, as you say, the 34DMTR (25/26 chokes). If your Lancia carb is worn out, Webcon do have stock of those by the way.

GC

HFStuart · Post by **HFStuart** » October 25th, 2007, 10:10 pm

Guy,

Thanks for the response. Peter Baldwin in Cambridge is going to see if he can do anything with it, if it is worn out I'll call Webcon.

Stuart

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Fiat 124 Weber 38 DGES

Fiat 124 Weber 38 DGES

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