'73 Fiat Abarth 124 Rally - project

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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 »

What brakes setup will we select?

Technically I would like the car to be fully in accordance with 1973 specs .

This would mean :

Brakes
Front : Calipers- Steel ATE 42 two pot
Disks : 256 x 12,4 unvented

Rear : calipers - Streel ATE 34 two pot
Disks : 256 x 9.6 unvented .

However, it is worth noting that the 1972 Appendix J is pretty liberal ( as compared to its later versions). Under art 266 , art, 260 and art.257 ( as applicable) the appendix J of 1972 allows multiple modifications or key systems including the following :

Braking system:
  • a/ the mounting of a double pump (master cylinder) or of any device which produces simultaneous action on the four wheels and a separate action on two wheels is allowed.
    b/ the discs and drums may be replaced by others provided the area of the friction surface is not modified.
    c/ the backing plates may be modified and fitted with air openings.
    d/ protection shields may be modified or suppressed.
    e/ cooling air-ducts may be added provided they do not entail a modification of the coachwork.
    f/ the mechanism of the handbrake lever may be adapted for obtaining an instantaneous unbolting (fly-off handbrake).
In such case “d” allows me to use a vented 256 x 20mm front disk and “a” and “f” allow me to install a separate hand brake BMC and a fly off hand brake mechanism.

Engine capacity: homologated 1756 cc (84 x 79.2) but appendix J allows for engine reboring which may increase engine capacity up to class limit (2,0 !!!)

Carburetors: homologated: Weber 44 IDF 20 or 21 on a waffle intake manifold .
(no change allowed)

Engine Lubrication system : homologated standard wet sump but appendix J allows liberal changes:
  • a/ the oil sump may be modified or replaced by another one of different shape and capacity.
    b/ the oil pump may be modified or replaced by another one. Yet, the number of oil pumps originally fitted cannot he changed.
    c/ oil filters and oil coolers are free (type, number and capacity).
This allows me to install an oil cooler.

Fuel tanks:
  • a/ the capacity of fuel tanks is free up to the limit specified under Art. 253 D( 100 liters) .
    b/ the location and dimensions of the filler orifice as well as those of the filling cap may he changed provided the new fitting does not protrude beyond the coachwork line and provides against fuel leakage into
    the inside compartments of the car.
    c/ should the tank and its filler be located in the luggage compartment, an outlet at the lowest point must be provided for the fuel accidentally spilled in this compartment.

This means that I can install a gr 4 later homologated 78 liters aluminum safety fuel tank.

Fuel pump: homlogated single electric fuel pump but by Appendix J : free as to number and type (will install two Red Top Facet pumps switchable from the dash )

Differential ratio : homologated 4.3 (43/10) and 5,375 (43/8). But ratios are free ,and so is LSD (but no permanent 100%).
With a number of gear sets sitting on a garage shelf - this can be changed depending on the event.

Gearbox - ratios are free, but I am not sure if my 2.0 CSO gearbox can be fitted onto the 1800 engine. this remains to be determined later.

Looks like an interesting setup with possibilities.

Miro

PS: Appendix J of 1973 at least partially explains why certain elements were not homologated in 1972. The 1972 appendix J remained valid until end of 1974

Note that many of these elements could be freely used between 1972 and 1974 but due to a stricter limitations on allowed modifications introduced by the 1975 Appendix J had to be homologated to continue using them.

M
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 »

Mick,

As regards dimensions of the "rear axis" I mean their length and diameter .

Incidentally you will know answers to my gearbox questions.

The gearbox I have is a standard synchronized 124 CSO.

I also have a spare 131 standard gearbox. But I suspect this will not fit the 1800 engine ???.

I certainly do not have a dog box for 1800 engine though a dog box is not my immediate target for the 124.

Any comments - suggestions ?


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Guy Croft
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Re: '73 Fiat Abarth 124 Rally - project

Post by Guy Croft »

The 131 5 spd will fit the 1800, starter and all, all the TC engines have common bellhousing mounts.

Ian Nixon (UK member badlyworntoy) is the best person to consult about race gearsets for that nice strong box as he has recently done it for his GC TC Lada. Probably the best bloke to build it too.

G
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Re: '73 Fiat Abarth 124 Rally - project

Post by Guy Croft »

The engine Mick is offering for sale is legal!

G
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Re: '73 Fiat Abarth 124 Rally - project

Post by Guy Croft »

according to my recollection this is the one, right Mick?

It was rebuilt in 2009 by me, a full-spec rebuild of a unit I built in th 90s and bought by Mick from that client.

Very low hours run since build as Mick said.

I think it will may pulley-belt upgrade to later generation system with wider belt and different alternator/crank pulleys.

Build data attached (non confidential copy just checked by me) in Excel format. Mick got approval to run the block with cast-in lower alternator bracket rather than the original 124 1800 detatchable one, I used this one with Mick's co-operation simply because of the scarcity of 124 1800 blocks.

G
Attachments
GC eng. 09.186
GC eng. 09.186
MW 8V_final build (1).JPG (551.13 KiB) Viewed 20121 times
MW 8V_final build (2).JPG
MW 8V_final build (2).JPG (509.39 KiB) Viewed 20121 times
MW 8V_final build (3).JPG
MW 8V_final build (3).JPG (516.53 KiB) Viewed 20121 times
MW 8V_final build.JPG
MW 8V_final build.JPG (619.27 KiB) Viewed 20121 times
Copy of 09.186 Parts and services _NON CONF.xls
(31.5 KiB) Downloaded 696 times
Guy Croft, owner
badlyworntoy

Re: '73 Fiat Abarth 124 Rally - project

Post by badlyworntoy »

Miro

I have lots of experience with Fiat 131 Gearbox's, Gear sets and Final drives In the 124/Lada Live axle.

The Fiat 124 gearbox is very poor in comparison to the 131 AB 5 speed as found in the 2.0 Mirafiori Sport (Racing in Europe) and as G.C says these are a direct fit to any Fiat Twin Cam engine so as long as your using the 215mm flywheel. Modifications to the car aren't so extensive either, so long as you follow the guidance of somebody like me who has done it several times, its relatively straight forward.

The Most major difference in performance between these two old gearbox's are that the 131 Gearbox uses large well designed toothed Syncro hubs which bite like a expletive_deleted, the 124 gearbox using the more antiquated brass bauk ring style synchronisers. The bearings are physically bigger, Input shaft bearing is similar size to 124 but all the lay shaft bearings and output shaft bearings are way bigger. 131 gearbox has zero bronze/brass bushes either....only needle roller bearings in there. Gear themselves are much better designed to and quality difference is clear to see when compared. Fiat really did a 100% job of improving them ready for the 2.0 engine in the 131. 124 5 speed gearbox's suffer terribly from wear under high performance use, I certainly wouldn't rely on one on a G.C engine.

I have never seen a 131 sport gearbox fail even after excessive Circuit driving!! its true that reverse gear can wear badly, as because like most RWD gearbox's they is no synchroniser on reverse gear However this isn't generally an issue and more of an annoyance. Simple precautions can be made to prevent this becoming an issue.

I currently run with a Bacci Romano C.L syncro Gear set in my Lada and used of course with the 131 gearbox. We are using G.C 2.0 StIII engine and to get the maximum benefit of this Close ratio gear set you must use at least 8000rpm on gear changes otherwise is a waste of time.

If your interested in the data from this I can post it sometime.

Nix
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Re: '73 Fiat Abarth 124 Rally - project

Post by Guy Croft »

expert advice there, thanks Nix,

G
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 »

Guy Croft wrote:The engine Mick is offering for sale is legal!

G
Guy

Dealing with you and Mick I would not expect anything else

Miro
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 »

Nix,

Thanks for your valuable input. You made it easy for me to know what box I want for my 124 - a 131 (2.0) gear box !

I would really appreciate your expert assistance in fitting it into the 124 spider chassis, and any other modifications that I will be facing.

Miro
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 »

Guy , Mick .

Looked at the pictures : awesome.

Looked at the specs and liked it even more.

Mick I think it is time we talked money.

Please reply to my PM.


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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 »

RE L pulley-belt upgrade to later generation system with wider belt and different alternator/crank pulleys.\I agree .


Guy

Fully agree.

I also have very nice adjustable cam wheels from Cat Cams which I hope would be useful for this project.
my cam wheels .jpg
my cam wheels .jpg (24.8 KiB) Viewed 19961 times
This project looks better and better ...

Miro
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Guy Croft
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Re: '73 Fiat Abarth 124 Rally - project

Post by Guy Croft »

Kindly DO NOT fit Cat Cams pulleys to my engine!

Thank you very much.

Mick's unit has GC design true-vernier STEEL pulleys already, made for me years ago by Titan.

G
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TomLouwrier
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Re: '73 Fiat Abarth 124 Rally - project

Post by TomLouwrier »

Miro,

Ah, you mentioned brakes :-)
I feel the numbers on the gp3 and gp4 front brakes can't be right. The calipers in the pictures are fixed type, whereas the original Fiat items (as on the Stradale and all other Spiders) are floating. This means that the quoted 2 pistons in the fixed caliper working opposite each other actually perform like a single piston in a floating caliper.
All this meaning that a 42mm piston on a 256mm disc will actually give less performance (87%) than the 48mm/227mm set.
If we consider the front to have 2x 42mm pistons effectively (2 in a floating or 4 in a fixed caliper) on said 256mm disc then the front brakes would have a 174% performance.

The rear retains the original 34mm caliper but on a larger disc, this combination giving 113% performance compared to the Stradale and all other Spiders.
This would not combine well with either of the front alternatives.

I strongly suspect the homologated caliper is 2x 48mm, floating. It would have the same performance from a hydraulic point of view as the Stradale, getting its better performance from the 113% bigger disc and the better dynamic properties that fixed calipers have.
Please prove me wrong on those 911 derived calipers?


Since you already have a 131-type box, use it! It's stronger and has better spaced ratios.
For street use I'm looking into improving the std 124 box (especially 5th gear which is way too short).

regards
Tom
Last edited by TomLouwrier on September 27th, 2014, 5:59 pm, edited 2 times in total.
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Guy Croft
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Re: '73 Fiat Abarth 124 Rally - project

Post by Guy Croft »

too clever for me dear Tom!!

G
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TomLouwrier
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Re: '73 Fiat Abarth 124 Rally - project

Post by TomLouwrier »

Not at all Guy, it's a very straightforward calc of piston area times disc radius.

T
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