128 RACING - Set up, Tuning and Repair...

[Abarthnorway - Remi L]

Hi Guy!

128 destined for racing now almost finished. Engine was started for first time yesterday night. After a short running in period the oil was changed and it was taken for a spin today. For Your information the car weighed in at 625 kg only!!!

First impressions:
Engine goes extremely well at higher revs - to put it mildly - even if it was not taken "all the way" - Yet....
The idle and bottom end - under 3000+- is a bit lumpy/rough with some hesitation and spitting back (all carb mouths equally bad) - especially when not fully warmed up. The idle was finally set at ca 1200 after turning out the idle jet screw about 6.5 turns...

1) This leads me to believe that I will need to increase the idle jet to 45

2) Or maybe advance the ignition a few degrees: currently set at 10` at idle as original
(I do not have a lot of experience very much about ignition - but this was recommended by "the mysterious someone" everyone refer to.....)

Your opinion highly appreciated!


Engine specs repeated here:

1290 cc SOHC
Everything fully flowed according to Your advice on forum
Slightly bigger exhaust valves
10,2:1 compression
Cams steel billet 10.5 lift actual, lift TDC 3.5, Lobe separation angle 106
Dellorto DHLA x 2
4-2-1 header into 1 7/8 straight through exhaust
Ignition (stock) 10`advace at idle

Jetting as recommended by GC:

DHLA 40 (no suffix)
Chokes 32
idle holder 9
idle jet 40
pump jets 40
emulsion tube 5
mains 120
air corr 190


More updated pictures descriptions will arrive after sundays race.

For full story regarding build take a look at:
viewtopic.php?f=5&t=1382




Engine bay - nearly finished




Car ready except for some minor details - weighed in race ready today at 625 kgs!!!




Genuine Dellorto jets for rebuilt DHLA 40 carbs



Best regards

Remi Lovhoiden

[Guy Croft]

Remi, hi

if the idle mixture screws are opened as much as that (6.5 turns) it could be that the idle jets are too small. However spitting back thru the carbs can be caused by retarded ignition too. If you've set it accurately, then yes, 10 deg advance at 850 rpm is fine.
Remember when setting idle mixture screws that the engine speed must be maintained at 750-850 rpm. Read Robert's post at: viewtopic.php?f=13&t=1424

Race carbs always spit and cough when the manifold and engine is cold, let the engine warm up at steady 2000 rpm and don't 'blip' the throttle because all you'll do spray loads of unwanted fuel into the cylinders from the pump jets. Once it is warmed up it should idle perfectly smooth, pick up instantly when the throttle is applied. If it doesn't, suspect pump jets not functioning properly or too small. It should be similar under load but from exp of that motor I would not expect it to take full load in second gear much below, dunno 3000 rpm?

Do not race this engine without plenty of plug tests taken from mid and full load/rpm driving. Or better still a mixture analysis on a dyno. If the mains and air correctors aren't right you will damage the engine thru detonation/overheating or bore-washing. Yes, I do my best to quote good starting points for jetting - but I didn't build up yours and you must check it's all OK.

You mention 'straight thru' silencer. I'd like to know exactly what it is. I assume your primary pipe pairings are 1&4, 2&3?

GC

[Abarthnorway - Remi L]

Hi Guy!


Quick update!

Some more testdrives today.

As it turned out I did not have the 45, only 48 and 50 idle jets - so we decided that we had to do the best out of the 40 idle jet.

We changed the idle jet holder from nr. 9 to a nr 2. This holder has fewer and smaller air holes in it - which means a richer tube. The change was immidiately clear. Idle became slightly more stable, but still slighty lean even with the idle screws 7 rounds out. The flexibility and throttle response in lower revs though - were clearly changed for the better:-) It now pulls cleanly nearly from idle, not a lot of power, but it does not stutter the same way as before.

The power now comes on really good from approx 5500 rpm, and goes like a scalded cat all the way to 7500/8000 with no signs of the power ending there. Instant throttle response!! I took some plug checks during the runs, and the electrode(?) was light beige/white, with the exposed plug threads being light "chocolate" brown - seems very good.

Due to the engine still being quite fresh, the absolute top end testing will have to wait till tomorrow. We also found that we had some issues with the cooling system - eeer - no need to go in detail, sufficient to say that tight time schedules makes the perfect breeding ground for mistakes.... will hopefully be fixed permanently tomorrow morning.

To set the idle jets with engine running at 750/ 800 rpm seems really difficult, as it just slows down and dies under 1000 rpm. Reason for this might be that the gasket for exhaust/intake manifold is not 100% tight. This is caused by the intake and exhaus manifold using the same nuts and studs for tightening. Even the smallest mismatch between inlet and exhaust manifold thickness will then potentially cause a leak. We tried to make them equal in advance with some serious grinding, so it would marry up perfectly to the head. The manifolds are both aftermarket items, from countries thousands of miles apart - so I didn`t really expect it to be the perfect fit..... Anyway seems to be satisfactory tight for now, but I will have to inspect it closely later. Any suggestions regarding "how-to-check" and "how to fix"??? (Pics next week after race...)

Regarding the term "straight through exhaust" it means that the exhaust goes in a nearly straight line from the 4-2-1 header (4/1 and 2/3 merge), through two oval "straight through" boxes (like 95 % af all performance boxes). We needed 2 boxes to get the noise under the 100 db noise regulations. I will upload some pics later.

Conclusion - So far very good progress.

Thanks to You and this forum for all help and advice!

Pictures and more results comes next week.


Best regards

Remi Lovhoiden

[Guy Croft]

Very good post!

All I want to say at this time is that with an idle mixture screw 7 turns out (if that is what it is) the tapered needle is not doing doing anything, the fuel metering orifice will be fully exposed...

GC

[Abarthnorway - Remi L]

HI GUY!


Engine performance under race conditions - Excellent!!!
Status after day - Disaster!!!

Weather was nice, with clear skies, and lots of beatiful cars. 26 cars competing at the start of season ranging from a 600 Abarth with 8 Port head and Autobianchi A112 Abarths, to Delta Integrale and Ferrari 308`s. Even my former Strada 130 TC Abarth is still running this series.

Well the day started with engine "boiling over" slightly, misting the engine bay. After some thought the coolant expansion tank cap was found guilty. The gasket under the cap had a rather big rift in it, and we suspected this to be the reason. This was fixed by applying a double layer of silver tape! Problem solved!

The warm up races went very well - with Stian and his small 128 beeing able to compete with some bigger cars like Alfa Gtv`s and Guilias. The 625 kg car proved itself to be a real racer on the twisty circuit. Engine sounds a bit like a bike engine on end of straights:-) The rev limit of 8000 rpm was with no doubt broken routinely .... Several plug checks done - they seemed perfect!

Anyway - in the heat of an intense battle with several other cars, a quick/harsh change was made from 3rd to 2nd before entering a tight curve, and engine suddenly lost some power. Stian finished off the next straight, but with very little power, before the engine was shut off. The car was towed into the pit. Something was definately wrong...

In the pit, we tried to turn the engine over by hand and it turned over fine, except very close to TDC - about 3-4 degrees where it definately touched something. Lots of theories flyed in the heated discussion that followed - loose exhaust seat, headgasket blown, stuck valve, broken valve, broken valve springs ++++. A visual inspection was made by taking off the cam cover, but nothing unusal to be found. What was for sure was that the engine had jumped some teeth on the cam belt at the crank end, as rubber dust was found in large quantities inside the cam belt cover, and cam was out quite a bit. To make it crystal clear - the cam belt was fitted tight - a bit too tight really. Still was after teeth jump.

The race was over for the day, and it was concluded to bring the car home to inspect in cleaner and more ideal conditions.

Head went off today - not by me - and inspected. All valves were intact, but all 4 exhaust valves had very small signs of hitting the pistons, but the pistons seems like new. The guides seems to have survived, but that will be checked closely later this week when I get to see the engine.

A lot of luck - and a relieved owner, and definately also the engine builder!!


This situation brings some questions to mind:


1) We suspect the harsh downshift from 3rd to 2nd to be the reason for the belt slipping at the crank end?

2) Will we be able to fit a wider and or stronger belt to prevent this failure in the future? If so is it OK to machine off the flange on the aux. driveshaft to fit a wider belt? Do You carry these? (Its actually a 115 teeth belt - shorter belt needed caused by milled block/head and limited travel on tensioner.)

3) Do You recommend us to inspect the pistons - if so how?

4) When sourcing new exhaust valves - do You recommend to upgrade to Uno Turbo exhaust valves, or will standard be ok?

5) Will the a standard headgasket be sufficient for racing conditions with 10.2:1 compression, or will we need to order another of race quality?


Thanks and best regards

Remi Lovhoiden




Stians 128 with with a 600 Abarth Replica with 1050 cc pushrod engine with 8 port PBS head and twin 40 DHLA`s. 128 now runs only 6 cm ground clearance (gearbox)






Engine ready for racing.





Abarth 8 port engine in Fiat 600





Stian inspecting the coolant expansion tank.





Two Lancias. Integrale with tuned 16v engine++, rather unusual race car at left - Thema Stationwagon 16V with competition cams and mappable injection/ignition - suprisingly fast car!!





Stian entering the track!





Stian stayed ahead of 2 litre GTV!!





Ferrari 308 GT4 on Stians tail - trying to overtake, but had to wait till long straight visible in the background.
GTV still behind:-)!!!





Torn cam belt after warm up races... sorry for pic quality





Cam belt cover now coverd in rubber dust.





Cambox cover removed nothing special here....





Team 128





128 in sunset - no more racing today - pity!!!





Race cars - all italian





Some more cars





GTV all the way from Sweden





As promised a pic of exhaust - 1 7/8 all the way from header outlet





Fuel cell and batterybox in rear.

[Acki]

Try a pipercam cam belt.

[Guy Croft]

Yes, Piper do a stronger belt but I've run OE belts for many years and not had this happen, which is by way of saying don't assume a stronger belt will help.

It's perfectly possible you got a stone under the belt, in the absence of other known cause - that would definitely make it jump. Look for an impact mark on the pulley. If you don't have a full undertray you need one. Don't rely on the std belt cover!

I don't anticipate any damage to bearings or pistons unless the impact mark from the ex valves is very severe. Just take out the valves and inspect them for 'true' and check the sealing on their seats. You certainly do not need s/c ex valves - the combustion chamber temperature is nowhere near high enough to justify that expense (high).

Look out for a shim come-out. You no doubt know that you must not put anything under the OE shims, they will tilt, and likewise 3.30mm thick is about the thinnest you can safely use before the cam nose hits the bucket. If you have top hats make sure they are still in place. I have never had one come out on GC 3VSR springs, so if one has, the rpm must have 'gone off the clock'. Do yourself a favour and buy an Elliot 'telltale tacho' so you see for sure what revs it went to. Drivers 'never' over-rev their engines - if you see what I mean! Until they have an Elliot tacho fitted...

See: http://www.elliotdesign.co.uk/index.html

You will be fine with the standard head gasket if you keep_the_operating_temperature at 75 deg C. Leaking header cap is not a good start!

GC

[Acki]

I think he has a pipercam cam pulley. Maybe the problem is the cam pulley.
I have seen pulley's where the cam belt do fit right in the tooth.

[Abarthnorway - Remi L]

Hi!

I think he has a pipercam cam pulley. Maybe the problem is the cam pulley.
I have seen pulley's where the cam belt do fit right in the tooth.

The belt slipped on the crank end.

Guy:

A 75`thermostat already installed.
Shims all between 4.30 and 4.40 - no other extras.
Will inspect engine closely on Thursday.

Are You suggesting that we re-use the exhaust valve if true/straight? No danger of valve material being weakened?


Thanks once again!!

Best regards

Remi

[Guy Croft]

Remi,

My method dictates that you should take all the valves out and face them up accurately with a valve grinding machine, it's the only way to assure that they are not bent.

Prior to grinding mark the contact face of each with black indelible marker, first you will notice that to remove the lapped contact face takes a second or two but if the valve is bent it will 'swash' and should be discarded. Valves always distort fractionally in service but no, if a valve is bent from a known impact I would not re-use it.

Sure you can blue-up and rotate them in their seats, roll them on a surface plate, leak test them in the head etc etc but I can say from exp that none of those methods guarantees to show up a bent valve..

GC

[Abarthnorway - Remi L]

Hi!

Just a quick update.

New valves exhaust valves installed quickly, and the car is now back on the track - Have been racing several races since with no problems whatsoever.

Thanks for all the help.

Best regards

Remi Lovhoiden

[Guy Croft]

Well done, a noisy google video would be welcome!

GC

[Abarthnorway - Remi L]

Hi All!


Sorry no videos.

Car won its class 2008 (Thank You Guy!)

The car was sold to Sweden after seasons end.
Regrettably no contact with new owner.


Remi