131 16v Abarth running badly

Road-race engines and ancillaries - general discussion
simon131
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131 16v Abarth running badly

Post by simon131 » August 31st, 2006, 9:11 am

Here are a few problems I'm having with my 1976 131 Abarth which are detracting from the pleasure of driving it.

I've never really been happy with the way that it runs. It's always had a flat spot on acceleration which hasn't been cured by cleaning the jets.

The engine is fitted with the standard single twin choke Weber 34ADF20-100 carb which according to the things I have read could be worn. The carb differs from that used on standard 2000TC 131/132s in the last two digits (20-100 as opposed to 54-250). I have no desire to swap out the single carb for twins, so have the following questions-

1) Should I replace the carb wholesale for a new one, or would a complete overhaul by a competent carb reconditioner suffice?
2) Where can I get a like-for-like new one?
3) Does anyone know a reputable, reliable carb reconditioner in the UK?

I also realise that the carb is probably only part of the story. I have looked at the distributor too, which has a habit of eating points, and am therefore keen to swap to electronic ignition. The distributor on the Abarth is driven by the exhaust cam, and therefore gets extremely hot. The points close with monotonous regularity, leading to extreme difficulty with 'hot starting'.

4) Is there a recognised quality supplier for electronic ignition replacements?
5) Does anyone know of reputable company who can take on both the carb and distributor work?


Your thoughts gentlemen (and ladies!) please.

Thanks

Simon
Fiat Abarth 131 Rally Stradale
Fiat 131 Racing
Fiat 131 S 1600 (x2)
Fiat 131 CL 1600 Auto
BMW 528i Sport (E39)
BMW 530i SE (Sporting) (E60)

sumplug
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Post by sumplug » August 31st, 2006, 9:36 am

Hi Simon.
Aldon Automotive are the people to sort your ignition problems. Been going for over 30 years and they produce bespoke distributors and electronic conversions for most cars. They are also a Weber agent too. Here is a link;-
http://www.aldonauto.co.uk/

The ADF is Not a good carb. Its strangling that engine. A change to a 32/36DGV as recommended by Guy is your way forward.

Andy.

Guy Croft
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Post by Guy Croft » August 31st, 2006, 10:14 am

Most likely it's the carb pump jet not working, or choke size fighting cam overlap, perhaps exhaust back pressure if it's not on straight-thru silencers.

Common problem on race engines.

I really need to open a garage and do cars! Anyone want to join forces?

GC

simon131
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Post by simon131 » August 31st, 2006, 10:24 am

Guy, if you do open a garage I'll be first in the queue!

Can you recommend a suitably sized carb for use in place of the ADF?

Sumplug, have you got first hand experience of Aldon Automotive? If so, what service did they perform for you?
Fiat Abarth 131 Rally Stradale
Fiat 131 Racing
Fiat 131 S 1600 (x2)
Fiat 131 CL 1600 Auto
BMW 528i Sport (E39)
BMW 530i SE (Sporting) (E60)

Guy Croft
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Post by Guy Croft » August 31st, 2006, 11:09 am

Well, as for carb, I'm not sure about this one.

Your Weber 34ADF (forget the model number suffix) is a carb with cast-in secondary venturis - or chokes diameter 24mm. Unless they have been bored and reprofiled bigger - near impossible to do in-situ.
I'd never use anything that small unless I was certain by dyno test that it ran with the rest of the engine setup, I mean depending on cams and how they are set up and exhaust header.

If the chokes are too small the negative wave on valve opening sees a restriction in the carb barrel instead of the big space at the end of the carb entry section and bounces back as a negative instead of positive (filling) wave. This could be the problem. I say 'could', see below.
Plus the airflow through a 24mm diameter orifice is relatively small compared to the inlet port flow on that cycle, especially as the valve approaches higher lift, the airflow thru the venturi can go trans-sonic and the fuel system doesn't work.

The 32/26 DGV is a good carb on an 8v TC up to a point, but with only 8% bigger choke area I'm not sure if it will be that much better, ie: cure the problem.

Question? Did it ever run well on the old carb? If yes then we're talking fault-finding. Just swapping to another carb is not fault finding.

H&H Ignition Solutions in the W Midlands are worth trying too, have found them helpful, but in the first instance you should run with what you've got, if it's wearing away points so easily it's either got the wrong coil or the condenser is worn out.

GC

GC

simon131
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Post by simon131 » August 31st, 2006, 11:37 am

Hello Guy,

Strange that you say that you wouldn't use anything so small in this application when Fiat fitted it in the factory(?).

The carb has always been a weak point on the car during my ownership and I've had trouble getting both the mixture right for the MoT and getting it to perform smoothly. The mixture has to be made richer after it's been to the tester so as to stop 'pinking' under acceleration.

I seem to recall having a discussion with you in the dim and distant past about the fact that a worn carb would always cause problems, hence my exploring this option. The carb on the Abarth is 30 years old after all, and hasn't had an easy life! If I could 'get away with' just renewing the jets then that's what I'd do.

As a comparison, my 131 Racing, which is fitted with a standard (8v) 1995cc twin cam with a single 34 ADF runs smoothly and accelerates strongly right thru the rev range. Infact my mechanic (Mark Nicholson of Italian Race Services near Basildon) and I are of the same opinion that the Racing is in fact 'quicker' than the Abarth! Something has got to be wrong!

Please help!
Fiat Abarth 131 Rally Stradale
Fiat 131 Racing
Fiat 131 S 1600 (x2)
Fiat 131 CL 1600 Auto
BMW 528i Sport (E39)
BMW 530i SE (Sporting) (E60)

sumplug
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Post by sumplug » August 31st, 2006, 1:09 pm

Hi Simon.
Yes, Aldon altered a friends Ford Distributor for his tuned Westfield about 4 years ago. Works perfectly with reduced advance. Their reputation amongst the racing brigade is very good. It's run like a family concern, so you get a very good personal service. I find the last bit a shade rare these days. Highly recommended. Infact, an SFC member is having his 2.0 8 v twin-cam Distributor rebult by them.
They could also recommend a suitable carb replacement for your worn carb.When you say its 30 years old, it makes me think how old some of these twin-cams are these days!!

Andy.

tmvolumex
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131 16v Abarth running really badly. Try installing a CD

Post by tmvolumex » September 1st, 2006, 7:17 pm

Simon,
Glad I found you, I see you have a couple of 131's!
First I¢ž¢ll try and help with your question. If your ignition points do not last long I would switch to a capacitive discharge, CD ignition system. I have used capacitive discharge ignition systems on my cars for more than 30 years. I started with a Delta Mark 10 unit which I believe was the first such system developed. The Delta Mark 10 had an ON / Off switch allowing you to switch between your conventional ignition and a CD at the push of a button. You could even do this while the engine was running. I now use a Crane HI 6 CD which also has multi-spark, built in rev limiter and boost retard (optional). The Crane system can be triggered by a conventional set of ignition points, optical switch, or magnetic pulse. CD systems only use the points for electrical triggering and not for switching high current, as a conventional point type system does. Because the points don¢ž¢t carry high current, when used to trigger the CD, they last the life of the point rubbing block. The CD also boosts the voltage to the coil from 12 volts to 450 volts giving you a much higher voltage spark. By retaining the points you can always switch back to your conventional ignition if you desire. I would check out your distributor, install and gap new points, lube it, put on a new cap and then install a CD unit. It¢ž¢s a good idea to change your spark plug wires at the same time as with the higher voltage spark, that CD generates, you will arc through any marginal spark plug wires. I would recommend replacing the plug wires with some 8mm Magnacore plug wires at the same time as you install the CD ignition. You will also need a tach adapter from Crane to get you tach to operate properly. When servicing your distributor, check for any oil intrusion inside the distributor from a bad distributor seal. If you have crankcase oil getting up inside the distributor you will need to change the distributor shaft seal. I always use a floropolymer (Viton) distributor seal as they last much longer than the low temperature nitrile or buna rubber seals. This is especially important for distributors located above the exhaust manifold. Floropolymer seals are rated for 120 degrees C; the other seals are rated less than 100C. Make sure the centrifugal advance weights move freely also. A Crane CD runs around $300 here in the states. MSD makes a similar CD system if you prefer.
Check out:

http://www.cranecams.com/?show=browsePa ... =6000-6400

I would make sure the ignition is perfect and then move on to the carb if the problem persists.
If you don¢ž¢t mind I have a couple of questions on your Fiat Abarth 131.
Do you happen to have a photo of your engine and carb / intake manifold layout? I have never seen the single carb system on a 16 valve engine.
Does your car have an independent rear suspension?
Do you have any pictures of the car you could share?

I hope this information is helpful.

Tom McGaffigan
1969 124 Sport Coupe
1976 131 2 door
1977 Lancia Scorpion
1977 Lancia Scorpion VX

Guy Croft
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Post by Guy Croft » September 2nd, 2006, 9:52 am

MODEL POST

Well done Ralph, an excellent example of one member offering detailed information to another in this situation, based on actual experience, with superb photos. I know myself that this takes some time to do properly.

GC

simon131
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Post by simon131 » September 4th, 2006, 6:40 am

Thank you all very much for your replies.

Tom, thanks for the advice regarding the ignition. This is definitely an option I intend to explore.

Ralph, your carb is very tempting,however following a detailed discussion with GC late last week the first thing I am going to try is a proper carb strip and clean, particularly the accelerater pump diaphragm and 'non-return' valve which GC reckons could be at fault. I have several ADFs laying around in my garage so may even swap the jets over from my Abarth's carb first.

Tom, regarding photos, I have numerous of the car, but not many of the engine bay (mainly because it's not the cleanest - what with it being a 'working car'!). I shall see what I can dig up out of my 'collection'. In the meantime though there are a couple of pics of the car taken at Castle Combe circuit back in late summer 2004 in the Readers Cars section of this forum. And yes, my car has independent rear suspension - it wouldn't be an Abarth without it ;-)

I shall keep you posted of any developments as and when I have the time to work on the car.

thank you for now

Simon
Fiat Abarth 131 Rally Stradale
Fiat 131 Racing
Fiat 131 S 1600 (x2)
Fiat 131 CL 1600 Auto
BMW 528i Sport (E39)
BMW 530i SE (Sporting) (E60)

simon131
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Post by simon131 » October 30th, 2006, 2:57 pm

Hello Gents,

Just to update a little on the status of my 131 Abarth.

Well, currently I can't get the thing to start at all now, so I'm not exactly what you'd call a 'happy bunny' at the moment!

So, if anyone knows where I can source a coil and a condenser for such a beast I'd be pleased to hear from you! I would also be pleased to have advise from anyone who has fitted electronic ignition to this type of car, with positive results.

Failing that, I'm now at the point where I'd be happy to have a genuine 'expert' look at it and put it right. The trouble is though that there are a great many people who call themselves 'expert' that couldn't do any better than my 6 year old!! I know, I've used them!
I'd gladly use Northampton Motorsport - but they are close to 100 miles away from me and I don't know how I'd get the car to them.

Any sugestions?
Fiat Abarth 131 Rally Stradale
Fiat 131 Racing
Fiat 131 S 1600 (x2)
Fiat 131 CL 1600 Auto
BMW 528i Sport (E39)
BMW 530i SE (Sporting) (E60)

Guy Croft
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Post by Guy Croft » October 30th, 2006, 4:18 pm

I'll pm you a phone number of an very good friend of mine - just west of London - with workshop, who can definitely ID - and fix the problems you are having.

GC

NickRP
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Post by NickRP » October 31st, 2006, 7:40 am

Simon,

unfortunatelly, I am too far away from you to provide any "hands-on" type of help.

I understood that you are having issues also with your ignition system. There is cheap and effective option for upgrading the points type ignition system. Basically, you't need to wire one of those ignition amplifiers used in cars with electronic ignition. I can help you with selection. Such items cost some GBP 30 new, and I guess you could source second hand one for some GBP 5. Wiring is trivial, as well. So if you are interested I could post details.

Of course, this will cure only electrical part of the problems, if your distributor has too much play, or is damaged mechanically in some other way, that would require sorting out first.

All the best,
Nikola Radenkovic

simon131
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Post by simon131 » November 13th, 2006, 10:53 am

Thanks for your input chaps.

The latest is that the Abarth is now sitting in a workshop in south London, having undergone a distributor and carb re-build.

I have not yet seen or driven the car since these works have been undertaken but will post a more detailed and (hopefully) technical report when I get the car back.

Suffice it say that the car now starts!!
Fiat Abarth 131 Rally Stradale
Fiat 131 Racing
Fiat 131 S 1600 (x2)
Fiat 131 CL 1600 Auto
BMW 528i Sport (E39)
BMW 530i SE (Sporting) (E60)

simon131
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Joined: June 23rd, 2006, 12:00 pm
Location: Farnborough, Hampshire
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Post by simon131 » November 21st, 2006, 1:37 pm

I collected the car on Saturday morning, and I am very pleased with the work carried out on the car, and am happy to recommend the chap who did it.

The work carried out was a full distributor and carb overhaul, including rejetting, also new Iridium plugs, new leads and a synthetic oil and filter change.

All of the faults apparent with the running of the car have now been fixed, apart from the hot idle roughness.

The chap who carried out all of the work was Mario Grech-Xerri, who runs a business called Performance Cars, in Tolworth, near Surbiton, Surrey. He was professional in all of his dealing with me throughout the repair process, and I am happy to recommend him.

I am told that this hot roughness is due to the shims being too tight after they have expanded when the engine reaches operating temperature. Guy, could this be the case? Also, Mario tells me that the shims can't be changed with the cams in-situ. Is this true for the 16v? I know that you can change the shims very easily in an 8v TC but I don't know about the 16v.

Thanks for all of your help Guy.

Simon
Fiat Abarth 131 Rally Stradale
Fiat 131 Racing
Fiat 131 S 1600 (x2)
Fiat 131 CL 1600 Auto
BMW 528i Sport (E39)
BMW 530i SE (Sporting) (E60)

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