Race Engine Forum UK

Now that 124 is back in my garage to enjoy , the works starts on 131 Abarth .

The current plans are quite ambitious and constitute probably the final stage of work to be carried out before the project can be considered "complete". Is there an end of the "never ending" story ? well I can see a light at the end of a tunnel. ( This is what LBJ used to say about the war in Nam, and the GI's used to joke :" yes , its the VC with a flashlight") . Well ,we will see ...

The program is this :

1. install Abarth sway bar (mounted to the front arms by drop links) and Abarth reaction rods (mounted to the arms where stabilizing bars are mounted in a standard 131).
2. put stronger clamps mounting the steering rack to cross member

3. get a new cross member and strengthen it like in Gr. 4
4. install reinforced steering rods
5. install Gr 4 shocks in the front with travel limiters
6. install travel limiters for rear shocks (Gr. 4)

7. develop proper springs front and rear (probably two sets)

8. adjust the Bilstein front and rear shocks ( compress/rebound) to less stiff specs (current is practically track only- too stiff for rallies).

9. weld strengthen the front and rear shock absorber turrets

10. install ATE (2 x 48) original specs calipers in the front
11. install ATE (2 x 38) original specs calipers in the rear
12. install Brembo hand brake caliper
13. install 300 mm or 275 mm disks (made to order based on Fiat 130 disks)
14. install 252 mm original Gr 4 disks in the rear
15. Install spring type protection for brake lines

16. install shock steering absorber (initial homologation specs)
17. install reinforced upper front and rear shock absorber seats.
18. install hydraulic hand brake (modification 26/24v to FIA homologation)
19. change internal fuel lines installation (to current FIA appendix J safety specs)

20. change the extinguisher system lines to (to current FIA appendix J safety specs)

21. change the infernal layout of electric brake and fuel lines (for safety reasons)

22. replace current door upholstered panels with light weight panels (like in Gr 4) (panels be installed will be fire proof)

23. removal of rear side upholstery panels

24. remove rear upholstered side panels with lights

25. correct minor electrical wiring issues in the cabin

26. Install light weight boot lid with rubber "lock" clips

27. install Torsen LSD

28. install stronger cv joints on rear axle

29. install full aluminum plate cover under engine


30. install Gr 4 type plate / cover on the long diff (its is already installed on the short diff).

31. change from stradale to Gr. 4 hangers of the diff cross member 32. correct support structure for the front "bumper" (currently any small hit risks destruction of oil cooler)

33. install high speed wipers assembly

34. Install Halda Twinmaster feed from left wheel ( gr 4 )

The plan is doing all this before mid August. With Robert this is more than possible. He is a real artist and true expert in classic Fiats performance sport preparation in accordance with original homologation specs. When this is done I will seriously consider taking part to Monte Carlo Historique... , after testing the car in Poland Rally Historique this September.

Wish me better luck than LBJ had !

Miro

21. change the infernal layout

Infernal or internal, Miro? Or maybe both... ;-)

I've already been punching in some numbers concerning the calipers and discs you've chosen. Just let me know when you need them.
Good luck with the program, you'll need it.

regards
Tom

Tom, you caught me still editing the text ...

Hopefully "internal" , but see ...

Please look at it again as I have just posted the final version ...

I would be most grateful for the numbers any time you got them. This time Robers , who does his own calculations will be able to really use it ( running it against his own calculations for developing the final brake solution for this car).

Actually we have discussed it at length this morning. It is really interesting that in doing that we need to consider a lot of variables:

1/ caliper piston size
2/ caliper type
3/ brake fluid pressure
4/ disk size
5/ disk friction area)
6/ disk pad size and kind
7/ diameter of brake lines
8/ brake pump size
9/ wheel size
10/ tire type and size

Ultimately some of the final determinations will really depend on empirical field testing of different setups.

Miro

Progress Update

I have reloaded the lost pictures , from the previous post.

Initial work started.

1/ The cross member was found and brought into the garage. It is in very good shape - fit for modification.

2/ The rear shocks were inspected and found to be in excellent condition. With softer springs and additional inner springs the rear suspension should have a better rally handling.

3/ Rear turrets were inspected and found in need of reinforcement. With no reinforcement present ( as it is now ) any major jump could cause the turret to fracture and the shock to come through the turret top. We will use brand new turrets (we have spare) to create second "outer layer" turret welded to the original one as part of reinforcement. This will be made very strong.

4/ The rear top mounts openings have larger diameter than the shock rods, making the shock loose in the uniball style bearing. We will attempt to put a fitment over the tip of the shock rod to make it fit the top mount. If this does not work we will manufacture a new special bronze ball with smaller opening to fit the shock rods.

5/ Front top mounts it the shock rods perfectly. The front turrets will be also reinforced

5/ The rear spring rested directly on the previous top mount. We will make a special strong aluminum dish to make the shock sit on it.

6/ The right longitudinal member was found to have a small old crack. I know the car had a small right side traffic collision in the past, this may be remnant of this collision as the crack seems to be quite old. (How come nobody has seen it before?). We will reinforce the both right and left members again to make sure they both are very strong.

7/ We are still awaiting verdict if the Torsen LSD will fit the diff ( keeping the fingers crossed).

8/ the standard bottom cast alloy bottom diff cover ( which has an oil plug sticking out of it) will be replaced with flat aluminum skid plate cover.
More progress with pictures as it comes ...

Miro

In the meantime ...

The 124 spider had a basic test done in a small club event. Handling proved to be excellent.
The car - now equipped with a thermostat matching the fan switch rating and a cleaned radiator keeps 85 deg temperature without any problems.

Torque and power seems fine for a street road car ( which it is ). The road homolgated four strap safety belts work fine and are very comfortable.

I have put a new steering wheel. Just slightly smaller and much thicker. Works great ! actually it is easier to drive witgh this wheel than the original one.

I have also taken out the useless clock and put an oil pressure gauge in its place. To complete the dash changes I have replaced US gauges ( speedo, puel and temp) with an European ones. It least the temp reading is clear - now in Celsius not Fahrenheit. Also the speedo now shows up to 220 m/h instead of 95 miles( MAX TOP SPPEED) .The 220 km/h on the closk looks much , much better better ! .

Some pictures to prove it:

as it looked before :
And as it looks now:
The hard top is really fine . It still is a bit noisy and requires use of some silicon spray lubricant to make it quite. But driving the car with the roof on gives me a lot of pleasure , specially since taking the front roof panels gives you a cabrio feeling without the back wind and with the safety of a hidden roll bar .

I am quite happy with the work result

Miro

Guy

I have a question on 124 block castings ;

I have found an 1800 DOHC engine with a block casting number of 132 AC 40 000.

The listings I have indicate this is an 1800 block used in 124 Abarths.

But the head is 8 valve.

Can you help making some sense out of it ?

Is there a way of recognizing if this is really an "abarth" block? Was it any different than standard 1800 block?

Does the 8 valve head fit on it without any technical issues?

Miro

Guy,

One more favor,

I need a picture of my engine from the exhaust side ...

I cannot find a picture like this . All side photos are on the intake side.

Can you help?

Miro

miro-1980 wrote:
8/ the standard bottom cast alloy bottom diff cover ( which has an oil plug sticking out of it) will be replaced with flat aluminum skid plate cover.

bottom diff cover stradale .jpg

bottom diff cover corsa .jpg

More progress with pictures as it comes ...

I understand why you would want to do this, but do you have a temperature sensor in your rear diff? I think it would be wise to monitor that the next few events to make certain you do not overheat the oil in there. I know that transaxle gear boxes are different, but they tend to get too hot on Alfa 75 cars if you race them and not cool them sufficiently. The same applies to several other brands. It's not your style to put sensors on everything and log them, but it may not hurt to find a way to check the temperature of the oil during or directly after an event, just to verify it's not overheating.

I've seen rally guys measuring the diff temp with IR temp gauge after the run. It gives reasonably accurate readings.

Generally, aluminium has many times larger thermal conductivity than ordinary steel/cast iron. And the temp isn't usually any issue even in cast iron axle in rally use bacause stages aren't very long. Of course it depends oil capacity, oil viscosity and internal friction of the diff.

IR-gauge, or classic 'tell tale' adhesive labels that discolour with temperature.
The Alfa transaxle contains the gearbox as well as the diff, which will generate more heat. Oil coolers on auto-boxes are common and many manuals boxes benefit from an alloy, ribbed sump plate like this Stradale diff has.
Some big BMW's have oil coolers on their diffs (can't remember which ones, will look it up), that would mean a form of oil pump as well. But it does show that diffs can get too hot, even with an alloy housing.

You're right about rallies usually having short/shorter stages of course.

regards
Tom

Gents ,

The thermal characteristics of alloy vs cast iron or steel discussion is most fascinating. This has put my attention to it and gave a reason to investigate the subject deeper and make a more informed decision. Before it was rater intuitive.

The reason for alloy radiator shape bottom plate of on the Stradale diff is clear. It will disperse heat better than a flat plate of the same material. Also because it has no oil plug sticking out and has a shape of a flat bad boat it is far less susceptible to damage when meeting with rock.

The car was homologated on 1 April 1976 under number 647 - 1/1v. Introduction of this plate was done as a second update to original homologation, and was dated July 1976 ( numbered 647 - 3/2v). The fact this was done in the fist series of technical specs updates suggests that Fiat copied this form 124 Abarth , maybe after initial tests.

From this I draw the following conclusion: actual tests and rally experience with this diff plate in 124 Abarth proved this to an effective protection against cracks after hitting a rock as well as not adversely effected the diff oil temperature.

If my thinking is correct I have nothing to fear. My rallies are fer less demanding and cover distances which constitute fraction of the distances these diffs went through under gr 4 rally conditions in 70's and 80's. Sorry to admit but I do not drive as aggressively as Sando Munari, Marku Allen or Walther Rohrl. My diffs have a fairly easy life with me (though they do not get serviced after every stage or every rally - just once a season)

Updates to homolation history for Fiat 131 Abarth rally clearly shows two elements were of deepest concern and greatest technical problem for Abarth : suspension ( which was almost constantly strengthened in successive homologation update as well as brakes which were changed n numerous updates. As this plate was entered once and never changed until the homologation expired i draw the conclusion: it required no correction. Hence I will not worry too much about diff overheating due to this plate.

I have the remote IR temp gauge and after this discussion I will remember to keep the diff temp issue in mind. I will test the diff temperature the next occasion with a remote IR temp gauge , just to get a feel for the temp it reaches after a stage or a hard test.

As I ma using very high quality diff oil especially designed for diffs with LSD and with high heat resistance I should be OK.

But the diff oil temperature is defiitly a major technical safety consideration and I ma glad you Gents brought it up.

Will keep an eye on this.

Thanks

Miro

Gents,

Does any of you have 124 Abarth FIA homologation you could share ?

I was trying to get to investigate reported use of 86 mm bore block in 124 spider and what I found amazed me greatly and brought some confusion into what I thought I knew:

# 1 Fiat 124 Sport Spider 1608 ccm (Group 4, 1970)
Engine: Four-cylinder row engine in front lengthwise (LM cylinder head), water-cooled; two valves per cylinder, two overlying cam shafts, operates by toothed belts; fivefold stored crankshaft, mixture preparation by two weber double carburetors 44 IDF; 1608 ccm, B x H: 80 x 80 mm, compression 10,5:1, 155 HP with 7200 R/Min, dry single plate clutch; Five-course transmission; Rear propulsion; self-supporting steel sheet body; Chassis: in front independent suspension at wishbones with thrust prop and coil springs; in the back rigid axle with thrust props and shock struts with coil springs; all around disc brakes; screw-roll-steering; Dimensions: 3970 x 1640 x 1240 mm, wheel base 2280 mm, track width v/h 1340/1240 mm; Unloaded weight: 920 kg.

# 2 - Abarth 124 Rally, 1756 ccm, eight-valve (Group 4, 1973)
Engine: Four-cylinder row engine in front lengthwise (LM cylinder head), water-cooled; two valves per cylinder, two overlying cam shafts, operates by toothed belts; fivefold stored crankshaft, mixture preparation by two weber double carburetors 44 IDF; 1756 ccm, B x H: 84 x 79.2 mm, compression 10,5:1, 165 HP with 7000 R/Min, dry single plate clutch; Five-course transmission; Rear propulsion; self-supporting steel sheet body; Chassis: in front independent suspension at wishbones with thrust prop and coil springs; in the back independent suspension at wishbones, semi-trailing arms and thrust props, shock struts with coil springs; all around disc brakes; screw-roll-steering; Dimensions: 3914 x 1630 x 1240 mm, wheel base 2280 mm, track width v/h 1413/1400 mm; Unloaded weight: 938 kg.

# 3 - Abarth 124 Rally, 1839 ccm, eight-valve (Group 4, 1974)
Engine: Four-cylinder row engine in front lengthwise (LM cylinder head), water-cooled; two valves per cylinder, two overlying cam shafts, operates by toothed belts; fivefold stored crankshaft, mixture preparation by two weber double carburetors 44 IDF; 1839 ccm, B x H: 86 x 79.2 mm, compression 10,5:1, 170 HP with 7000 R/Min, dry single plate clutch; Five-course transmission; Rear propulsion; self-supporting steel sheet body; Chassis: in front independent suspension at wishbones with thrust prop and coil springs; in the back independent suspension at wishbones, semi-trailing arms and thrust props, shock struts with coil springs; all around disc brakes; screw-roll-steering; Dimensions: 3914 x 1630 x 1240 mm, wheel base 2280 mm, track width v/h 1425/1445 mm; Unloaded weight: 900 kg.

#4 Abarth 124 Rally, 1839 ccm, 16-valve (Group 4, 1974)
Engine: Four-cylinder row engine in front lengthwise (LM cylinder head), water-cooled; four valves per cylinder, two overlying cam shafts, operates by toothed belts; fivefold stored crankshaft, mixture preparation by two weber double carburetors 48 IDF; 1839 ccm, B x H: 86 x 79.2 mm, compression 10,5:1, 180 HP with 7000 U/Min, dry single plate clutch; Five-course transmission; Rear propulsion; self-supporting steel sheet body; Chassis: in front independent suspension at wishbones with thrust prop and coil springs; in the back independent suspension at wishbones, semi-trailing arms and thrust props, shock struts with coil springs; four disc brakes; screw-roll-steering; Dimensions: 3914 x 1630 (running version for the road employment widened: 1730) x 1240 mm, wheel base 2280 mm, track width v/h 1425/1445 mm; Unloaded weight: 900 kg.


# 5 - Abarth 124 Rally, 1839 ccm, 16-valve-injection (Group 4, 1975)
Engine: Four-cylinder row engine in front lengthwise (LM cylinder head), water-cooled; four valves per cylinder, two overlying cam shafts, operates by toothed belts; fivefold stored crankshaft, mixture preparation by mechanical ball fishery squirting; 1839 ccm, B x H: 86 x 79.2 mm, compression 10,5:1, 210 HP with 8000 U/Min, dry single plate clutch; Five-course transmission; Rear propulsion; self-supporting steel sheet body; Chassis: in front independent suspension at wishbones with thrust prop and coil springs; in the back independent suspension at wishbones, semi-trailing arms and thrust props, shock struts with coil springs; all around disc brakes; screw-roll-steering; Dimensions: 3914 x 1630 (running version for the road employment widened: 1730) x 1240 mm, wheel base 2280 mm, track width v/h 1425/1445 mm; Unloaded weight: 900 kg.

I come form region and the times that taught me not to believe everything I hear or read , but this is interesting. What is normally regarded as the 124 abarth had at east two set of tech specs. One was based on BS series 124 spider with 1608 8 valve engine, had a standard rear beam axis and a Collotti gearbox. The other was based on CS model with 1756 cc engine , 16 valve head, independent rear axis , and the rest of what most of as makes a real 124 Abarth. Note that reportedly both had gr 4 homologation.


My research into FIA homologation of 124 versions gave the following results:
Unfortunately I have fund no reference to the early BS based 124 Abarth called : Fiat Abarth 124 Spider Rally. This may be # 1 (above).
The # 2 and remaining ones could be versions of the CS based 1800 Abarths most of us know .

But this would be the first time I have heard that 124 Abarth had as much as 1839 cc and used 86 x 79.2 mm pistons.

Can anybody comment and make sens out of all this, refer to literature, provide homologation documents for any of the cars #1-#5 ???

Miro

If you are going to assume that you are okay with leaving the diff this way, you should follow the maintenance and replacement schedule that Fiat had as well. It could very well be that they replaced diff oil after each rally and rebuilt diffs every three events or such? Their specs could very well be based on the "as long as it gets us through one event" wear limit.

I do know that no matter how good oil you get, once you "cook" it, it's useless and needs to be replaced immediately. Modern full synthetic oils can take a higher temperature, but once you cross that line, they deteriorate much quicker due to the more uniform chemical composition. Taking temperature probings right after the event is a good way to determine how hot your diff oil gets, but don't overestimate the heat resistance of your diff oil. Modern chemicals can do a great job at protecting and lubricating your gears, but the things oil manufacturers have to do to get that good, usually mean that the difference between great oil and chippy fat is only thirty degrees or so.

That is where those adhesive 'tell tales' come in: they discolour to the point of the highest temperature reached during the event. Your diff may cool a lot between the heat -literal!- of the battle and the moment you take your IR reading.
As far as I can see the entire diff housing is alloy, with a good oil reservoir along its length. Iron plays no heat conducting role here.

I have no proper literature to prove it, but I have read from several sources on the web that Fiat campaigned a number 124 BS Spiders as a 'proof of concept' under a thin cover of 'private entries'. A season later they launched the official 124 Abarth and works teams.
The 1608 was developed specially for this goal, reputedly by Abarth in order to learn more about the engine. Considering the double IDF setup, bronze valve guides etc I think this is quite plausible. Somehow it seems way too expensive and over the top for just a nice sporty roadster.
Of course the introduction of the 132 block with scope for much bigger bores gave Abarth the 1800 option which they took and which was homologated.

Nice to see that my 1608 could be making some 150+ HP but would I like it in traffic?.... :-)

regards
Tom

WhizzMan wrote:If you are going to assume that you are okay with leaving the diff this way, you should follow the maintenance and replacement schedule that Fiat had as well. It could very well be that they replaced diff oil after each rally and rebuilt diffs every three events or such? Their specs could very well be based on the "as long as it gets us through one event" wear limit...

This is an extremely valid point!!! Something to be kept in mind with respect to all other aspects of rally preparation of my car. I will certainly keep this in mind ! Thanks WhizzMan , indeed.

I do not usually have a full ex-factory Abarth service team backing me up with unlimited stock of parts including a dozen diffs ..., I do not change oil after every event and o not rebuild the diff/LSD after every three events. Not that with my type or rallies I would need all this , but nevertheless : I do not

In fact until this discussion my appreciation of diff oil temp was limited to research on good LSD oil ad getting it.
I have no idea to what temperature the diff oil gets in my car, but I would hate to put another gauge in it. During the event I do not see gauges at all just red lights - too busy keeping my eyes on the road/track. So the gauge would be in effect useless ...

But the solution Tom offers is a good and simple one giving us an idea of the temp wear of the diff. It will work as the highest temp will be recorded and can be read after the event, when the car goes to post event service.

I do not think I drive like Munari , Allen or Rohrl , and the events are amateur (far shorter shorter, and less demanding). Nevertheless this is something to keep in mind and have some sort of good reading. The paint which changes with growing temperature seems simple and convenient indication of thermal wear of the oil.

I am using what I believe to be the top LSD diff oil ( Motul 75w-140 ) which has the following specs:

Viscosity grade SAE J306 75W-140
Density at 15°C (59°F) ASTM D1298 0.906
Viscosity at 40°C (104°F) ASTM D445 170 mm²/s
Viscosity at 100°C (212°F) ASTM D445 24.7 mm²/s
Viscosity index VIE ASTM D2270 178
Flash point ASTM D92 212°C / 413°F
Pour point ASTM D97 -36°C / -33°F

It is probably by far an overkill for my diff and the way I drive the car , but such wide safety margin is what I like.

Miro

Any suggestions where to get this paint at a reasonable price.