131 Abarth spark plugs

[Peter de Wit]

I ran into the following problem: After running at idle for 20min to go over some start ramp, I had constant misfires and no power at all. Changed the spark plugs to fresh ones and it was solved. But it surprised me. Had not run into spark plug problem since abandoning Golden Lodge's for Alfa Nord engines.

I use NGK V-power nr7's. What other ones should I try? These were trouble free for 1000km though.

[Guy Croft]

You should be on NGK Race Div part B9EGV.

I am an agent for these.

If it it doesn't run properly on them there is some problem with compression/calibration - because it should run flawlessly.

I don't approve of using road plugs in race engines, no ho.

GC

[Peter de Wit]

Thanks, that makes things easy! Given that they are a 'race type' I would image they conduct the heat better. But would you say I would not have the same problem of them fouling at idle as I had?

And what would you suggest for the leads?

[Guy Croft]

Peter,

you will not encounter any fouling problems at all if the fuelling is calibrated right. I have dynoed over and over with these under all possible conditions. If your fuelling is overly rich you need to address that - not, if I might just remark on it - fit er, 'hotter' plugs.

As for leads my own preference is based almost entirely on leads that don't 'part company' when you pull them off. Unfortunately NGK stopped making theirs years ago and I don't 'dress' engines these days so never buy them.

Over to other members for recommendations?

GC

[Peter de Wit]

I run too rich for sure! Will open a separate topic on whether 48IDFs are suitable for my engine.

As for leads, I am open for suggestions from others. Agree with Guy that the ones that separate when you pull them off are a pain.

[miro-1980]

Peter

I assume it is a two liter.

Provide some details engin , esp. port sizes, valves, camshaft, also on extractors diameter.

It has bee generally the experience that the best are 45 DCOE's if you can fit a siderdaft.

You can also look for soled 45 sidedraft whcih are a little smaller and more dependable (require less frequent adjustments)

48's seem a bit too large ...

Miro

[Peter de Wit]

Thanks for the help here, Miro! Let me try to make sure the ignition is tip top, test that and come back with the carburation topic. I will make some pictures of the setup and problems there. In the mean time, could anybody let me know what other distributor I could fit in the abarth head? The car is 30+ years old, has done 53k kms and really nothing has been changed/updated. I noticed tremendous play on the advance weights. Will try to get an old Sun distributor tester to work next weekend and plot the current advance curve. Could not imagine that is OK either.

Questions open for now:
- advice for leads?
- will other (hopefully more modern) distributors fit?

Thanks! Pete

[Guy Croft]

I could do with the full engine type/spec Peter! All I know is what's published at:

viewtopic.php?f=5&t=1835

Can't diagnose if I don't know that,

GC

[Peter de Wit]

I wished I knew what was in there.... I cannot trace any of the previous owners who really worked on the engine. It were all collectors. If you could let me know what I can do to find out more about the engine, I will do so. I am at the point to taking the head off to inspect it. But it would be no problem to degree the cams for instance.

The engine nr is 131AR000000008x, x being a digit 0-9. But this nr is on the block, not the more relevant head. Head is the std 16V if you ask me. Inlet manifold is an Abarth 90 degree manifold with polished ports of 44mm. On this sits a ruber flange going from 44 to 48mm. On this the 48 IDFs with short trumpets covered with mesh (sorry....). Exhaustmanifold is std (16V inlets, a meter length). Distributor is on the head with Magnetti Marelli transistor unit. All in all it looks rather stock to me. But again, if you have checks for me to carry out, let me know.

Then some progress on the ignition. Managed to get the Sun 504 distributor tester working today. Measured the advance of Fulvia 1600 distributors vs 1300 ones. Never done this before, but a great eye opener. From now on I would really want to set the ignition only with a strobe at 5000 or so revs instead of 800 as I did before. The advance at low revs is so progressive that you introduce an error too soon. I am sure there is a procedure that Guy described, will look for that. But what I did find is that spark plugs I used do not spark the way they should anymore. They sparked over the insulator, not to the tip. Those are binned.... Next I will take distributor out and test that. Would anybody know the advance curve for a std Abarth?

For the record, I found good leads with fixed ends. Will get those and fit it. But first test the distributor.

[Guy Croft]

At this juncture I want to say that unless that 16v head is supertuned (eg: by me though I sternly resist modifying original Abarth) and the cams very radical (which few have) it will likely not give optimum power on 48IDF. Over-carbed (so to speak) can result in overfuelling and poor throttle response, low torque etc etc.

My strong advice in the first instance is get hold of some 44 IDF Webers and try them with 37mm chokes.

I do not know where peak advance should be but anything from 3800 to 5500 will be OK, just see where it lies with a strobe test. Static advance (ie: the preset distributor position at 900 rpm or lower - before centrifugal comes in) should be 8-12 deg and the max advance (sum of static and centrifugal) somewhere between 28 - 30 deg. In other words if you're testing the distr on the test bench the weights should give about 18-20 deg. Those 16v units need less advance than TC 8v units.

GC

[Peter de Wit]

Thanks Guy, I have enough action items to work on! Will redo ignition thoroughly. Will fit 44IDF's. And give it a good tune up.

I remember you writing that IDF's could be mounted without MISAB spacers. Is that correct?

Also, what is the difference between IDF 70 and 71? What to go for?

I have about 3inch between the top of the carbs and the bonnet then. Bonnet has air scoop above the carbs. What type of air filters should I use?

And last question, you said you would not tune the actual Abarth unit. What kind of 16V would you then take??

[Guy Croft]

Also, what is the difference between IDF 70 and 71? What to go for?

The Weber IDF 44 used on the 124 CSA for example was 44IDF 20 (front) 21 (rear). The current new 44IDF from Webcon in the UK, see:

http://www.webcon.co.uk/weber/performance_carbs.htm

is only aval as 44IDF 70. Those are type numbers and basically all 44IDF are the same so take what you can get. Obviously you have to buy things like chokes (or make your own, ie enlarge from max aval size 36mm to 37mm) and jets etc to suit your application.


I have about 3inch between the top of the carbs and the bonnet then. Bonnet has air scoop above the carbs. What type of air filters should I use?

That layout would be best served by an OE Abarth or 124 Sport 1608 'turtleback' filter (see sales section, there is a photo in there somewhere). Otherwise enlarge the bonnet scoops and fit the tallest K&N they make. The struts do fracture after a couple of years but there's not better filter. I would point out that for years I have been stressing the absolute vital importance of ducting from atmosphere to the carbs via a large remote type filter sealed airbox and - in short - you should consider this carefully. Doing this gives more power and completely rules out any detonation problems due to overheating intake air. And YES - everyone says to me, because of the effort involved in the solution I've outlined, 'I've got a tube going to the carbs feeding cold air 'over them'. But it's NOT the same thing and is not effective at all. A brief survey of the underhood temp after a full power run will amply demonstrate what I am talking about.


And last question, you said you would not tune the actual Abarth unit. What kind of 16V would you then take??

I will overhaul Abarth prepared units but not modify them - unless they have been 'butchered' by some amateur (it happens) - in which case I tidy them up. Given that in overhaul it is necessary sometimes to replace rods, pistons, guides etc apart form necessary work to assure fit-for-duty I take the firm view that those are historic units and should be left in original state. Like any valuable object, altering them just devalues tham completely. Naturally from time to time (as I have featured in the GC V/W) I get raw Abarth stuff to work on which requires a full set op GC modification ops to bring them up to the standard they would have been if finished at Abarth (or better)...

GC