Fiat 125 race car (& others!) in western Australia

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Guy Croft
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Fiat 125 race car (& others!) in western Australia

Post by Guy Croft » Wed May 11, 2011 1:00 pm

Kindly sent to me by Steve Boyle:

http://www.youtube.com/watch?v=n5hVoJLJCp8.


"This is a clip from an event in April this year. Here in Western
Australia we have 2 "Round the Houses" events where they close the
centre of a country town and let us loose on a circuit bordered by
concrete barriers. They are run as regularity events where you nominate
a time and the competitor who circulates closest to their nominated time
wins. We must not "race" or we get "smacked" but no one says we have to
nominate a slow time, so some us don't. They are great fun events and
provide some variety in a state that only has 2 dedicated circuits. I'm
chasing a Porsche and an Alfa until my engine temperature says slow down
( it was 36degC on the day) . This is with the 1800 on the DCOE40's with
the Dellorto auxiliary venturies and 36 chokes we spoke of..."



Watch. Pure music!

GC

S&B125
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Re: Great vid of 125 racer in

Post by S&B125 » Thu May 12, 2011 7:18 am

Thanks Guy
I thought I might provide some information on the car/engine spec as seen in the video.
The car is the "other" 125T in Australia and resides in Perth, Western Australia. At present it is fitted with a 1780cc engine which I built to go in to another car and to allow me time to rebuild the 1608cc originally fitted.
My plan when building this engine was to take advantage of as many parts laying around in the shed as possible, to keep the cost down, while taking advantage of the inherent strength of the standard components.
Specs are:
Engine 132AC100 (124 Sport CC Eng)
Bore/Stroke 84.6/79.2 = 1780cc
Pistons Cast 8mm Dome 1585 Regata (inlet Valve reliefs enlarged)
Rods Std
Crank Tapped, Plugged & Balanced
Sump Enlarged with wings & baffled 16 row oil cooler
Fywheel Lightened & dowelled as per GC instuctions @6.15kg - Balanced
Clutch Std
Comp Ratio 11:1
Cams Inlet 300deg 10.5mm lift Timed@106deg Exhaust 292deg 10.5mm lift Timed@110
Valves 43 -37.5
Carbs 40DCOE 36 chokes
Exhaust 41mm Primaries 430mm long 44mm Secondaries 430mm long 57mm tail pipe.
125T4036.pdf
(16.91 KiB) Downloaded 273 times
Power See attched chart 147hp (Din) @ 6720 Torque 170nm @ 5020
This engine has run with DCOE45's with 38 chokes and produced 157hp (Din) and 174nm @ 5480 & will again.
GC_35 Fiat 125T

S&B125
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Joined: Mon Nov 27, 2006 6:57 am
Location: Perth, Western Australia
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Re: Great vid of 125 racer in Australia

Post by S&B125 » Tue Sep 06, 2011 11:31 am

Some new video from a sprint we held in conjunction with the Targa West tarmac rally event. This took place on the foreshore of the City & the Swan River held on the 28-08-2011. This is the 2nd last event for the 1800 (the 1608 is ready now).
http://www.youtube.com/watch?v=ZYp8su86ARM
GC_35 Fiat 125T

S&B125
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Re: Fiat 125 race car (& others!) in western Australia

Post by S&B125 » Tue Nov 29, 2011 1:35 pm

I thought it was time for an update on progress with turning the 125T back into it's original specification. I know it sounds wrong on a forward looking forum like this write about returning a car to it's 1972 specifiaction, let's just say it's "conforming to a set of rules". Those of you with experience competing in HISTORIC Motorsport in any juristiction will probably understand.
The original 1608 eng which was in the car when I bought it is the subject here. According to the documentation which came with the car, this engine was built in 1991 & 1992 in Auckland NZ. It is referred to in as the "Demon Engine" and was fitted to the then current NZ Historic championship winning car. By the way if any Kiwis out there know facts which coflict here please let me know, I'm going on the information that came to me with the car and would love to here any info regarding my Fiat 125T reg No GG7963. Some Photos

This post is about the rebuild of an engine which was pulled out while quite healthy. I thought "I can't just keep swinging this thing forever" after 18 months of active competetition in 2008 - 2010.
Attachments
DSC_0421.jpg
At the Fiat Nationals 2011
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DSC_9538.jpg
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DSC_9541.jpg
DSC_9541.jpg (24.13 KiB) Viewed 4460 times
GC_35 Fiat 125T

S&B125
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Location: Perth, Western Australia
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Re: Fiat 125 race car (& others!) in western Australia

Post by S&B125 » Thu Dec 01, 2011 7:05 am

125A series 81 x 80
This engine was producing 135HP@6860 and 150nm@5230 when it was pulled out for a freshen up.
The most interesting aspect of this engine I noticed when stripped was the custom pistons which they had made.
TDOMES.JPG
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They have very high rounded domes are forged and nice & light. The rods had been lightened nicely and had been coverted to full floating gudgeons with teflon buttons. The cylinder head had been "shaped" on the sides of the combustion chambers to clear the wide domes.
TPISTONS.JPG
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I don't believe these pistons are the way to go I'm just posting this for interest. This rebuild was done to keep the car in competition while I build a fully prepared race engine and as a test mule for the exhaust & induction system. The main changes made during the rebuild were to valves & valve seats to test what gains come from this.
GC_35 Fiat 125T

Guy Croft
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Re: Fiat 125 race car (& others!) in western Australia

Post by Guy Croft » Thu Dec 01, 2011 12:53 pm

I'd be interested in the state of the teflon buttons. Never found them very survivable really.

G

S&B125
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Re: Fiat 125 race car (& others!) in western Australia

Post by S&B125 » Fri Dec 02, 2011 1:01 am

I had not had anything to do with them before but found them to be in what appeared good condition with no flattening on the domes and the fit in the pin seemed fine. I reused them in the rebuild. I wish now I'd taken some photos of the setup. This whole engine (appart from the valves & valve seats) had suffered so little wear the decision to rebuild as is was taken.
THEAD.JPG
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Not quite to the standard of presentation seen elsewhere in this forum though the preparation was done with great care and attention to detail where the valve & valve seat areas are concerned. The valves are used original 42.4 in and 36 ex. The head had been previously ported, not in exactly the way we would now but I was'nt going to "ruin" another good head by modifying it to suit these pistons.
GC_35 Fiat 125T

S&B125
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Joined: Mon Nov 27, 2006 6:57 am
Location: Perth, Western Australia
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Re: Fiat 125 race car (& others!) in western Australia

Post by S&B125 » Tue Dec 06, 2011 2:15 pm

A further update on progress with the rebuild. Guy has expressed concern (well founded) with supply of "decent" head gaskets for the old 80mm bore engines. I certainly had to talk to some mates and go through a couple of gasket sets to find this one. If anybody has knowlege/experience with these gaskets (pictured) good or bad - please comment.
Gasket(600 x 337).jpg
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Here is another photo showing the lightening of the conrods and the assembled bottom end.
Bottomend (600 x 337).jpg
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The build continues apace with a "freshen up" of the engine bay undertaken. It was looking a bit tired after quite a few years of competeition.
Tbayprimer (600 x 337).jpg[/attachment Painted after quite some work [attachment=2]Tfrontprimer (600 x 337).jpg
The engine fully dressed (photo oprtunity) and ready to install.
With the "Original Universal Performance Dellorto DHLA" carbs - they really are that much better than the later "emissions" type DHLA40 carbs originally fitted to Alfas. Particularly in the progression phase, tuneable and forgiving is probably the best description. The ram pipes (tubes or air horns etc) are as fitted to the GTA Alfas and allow me some extra lenghth by being able to swivel and get around the shockie tower.
Tengdressed.jpg
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Attachments
Tbayprimer (600 x 337).jpg
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Tfrontprimer (600 x 337).jpg
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Tbaydone (600 x 337).jpg
Tbaydone (600 x 337).jpg (38.81 KiB) Viewed 4386 times
GC_35 Fiat 125T

Guy Croft
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Re: Fiat 125 race car (& others!) in western Australia

Post by Guy Croft » Tue Dec 06, 2011 3:32 pm

Those early head gaskets are OK (in the broadest sense), keep the motor cool (75 deg C) and they will last pretty well - till the fire ring gives up. I've run a 160bhp + 1800 on that style in the past.

In my exp FWIW they last a lot better with 12.9 grade head bolts like mine..

G

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Re: Fiat 125 race car (& others!) in western Australia

Post by Urbancamo » Tue Dec 06, 2011 8:55 pm

Nice car for sure and love that classic sound track...!

But my eye cathed that inlet manifold and carb orientation. Webers and Dellortos too should be mounted in 5 degree upwards orientation, and maximum permitted angle is 7 degrees.
Of course picture might fool a little bit, but just curious, just curious...

T
GC_25

S&B125
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Re: Fiat 125 race car (& others!) in western Australia

Post by S&B125 » Thu Dec 08, 2011 1:57 am

I've had 3 different manifolds and 3 different sets of carbs mixed and matched in this car and never found the angle of the manifold to be an issue. Initially I was concerned by the angle but subsequent use and testing have revealed no issues when using Webers or Dellortos.
TENGTOP.JPG
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I also had to fabricate my own headers (as I couldn't buy any). My attemp is pictured - they 41mm OD primaries with a length of 450mm +/- 10mm. This was as close as I could get them within the available space. The secondaries will be 44mm OD and also 450mm initially but I will try some different length secondaries as time permits.
THEADER.JPG
THEADER.JPG (52.45 KiB) Viewed 4120 times
GC_35 Fiat 125T

Guy Croft
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Re: Fiat 125 race car (& others!) in western Australia

Post by Guy Croft » Thu Dec 08, 2011 9:47 am

Enjoying this thread a lot. I've spoken to Steve (is thread) several times - no doubt in my mind as to the sanguine competence and skill at work here!


G

S&B125
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Re: Fiat 125 race car (& others!) in western Australia

Post by S&B125 » Thu Dec 08, 2011 11:17 am

One of the main aspects of this rebuild was to test the effect of slowing down the water pump and alternator. You will see from the photo of the front of the engine that the front pulley is of significantly smaller diameter than standard (down from 146mm to 100mm). This has reduced the speed of the water pump, which according to my maths on the original gearing was doing 5900RPM to 9500RPM when I used the engine between 4500 - 7500 in competition. The water pump now does between 4000 -7000 RPM, which is much closer to the speed the engineers who designed it had in mind. A smaller/lighter alternator was also fitted for purely weight saving reasons. A tip for anyone doing this type of modification to the front pulley is when you install the TDC pointer and mark you're TDC position, also place another mark @ 35 deg BTDC for later checking you're full advance. I know 35deg may not be absolutely optimum but in my experience you wont be far wrong at that figure on on of these old girls running points. As a matter of fact when the subject of ignition timing comes up in conversation with my mates here I always say I have 35deg max advance and what ever the spings pull it back to at idle. I also prefer the dissies which have only 20 deg of mechanical advance as this gives me a static of about 15-16 deg at idle. When running race cams with high overlap this tends to make them slightly more tractable with no hard starting and no pinging.
GC_35 Fiat 125T

S&B125
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Re: Fiat 125 race car (& others!) in western Australia

Post by S&B125 » Fri Dec 09, 2011 5:58 am

We have some results on this engine now. It's been run for a couple of hours on the road and through 5 complete heat cycles. I like to run new engines slightly on the lean side - 13.8-14.5:1 when the engine is very young, say the first 2-3 hrs use when bedding in and not too much load is used. The head has been re-torqued and the mixtures are now set to give from 12.8-13.8:1and we are ready for full throttle testing.
As stated above this engine was giving 135hp@6860 and 150nm@5230 see attached sheet for the results on the rebuild.
T40D1.JPG
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You will notice we have found 11hp and 12nm. Interestingly this has come only from careful attention to valve seat work and perhaps the headers I made may be an improvement (though I'm no experienced expert in that area). Very pleased with results. Guy is right to stress the importance of this area of engine building. By the way all tests were carried out on the same Dyno/rolling road before & after. They are corrected to DIN specs and for those who only ever look at the power @ the wheels figure, the graph has this displayed in kw so 95kw = 128.5hp at the wheels.
GC_35 Fiat 125T

S&B125
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Re: Fiat 125 race car (& others!) in western Australia

Post by S&B125 » Fri Dec 09, 2011 7:14 am

Having read this thread from the top I feel I must give a bit more detail about the spec of this rebuild for reference.
The engine has the same : block, crank, rods, pistons, head, cams, sump etc as it did before. The cams are timed @110 deg exactly as before (this is dictated by the exsisting cutouts in the pistons). So therefore the only changes are to the valve throats / valve seats and to compression. The compression difference came about because it was noticed that the pistons did not come up to deck height, so the block was decked by .030" to bring the pistons up. Again I wouldn't normally do this in a fresh build (I'd have the pistons made properly) but this block was already at 1mm O/S and was "going again".
The comp ratio went from 10.16:1 to 10.65:1.
125A: 81 x 80 1649cc
Cams: 300deg 10.5mm lift
Carbs: Dellorto DHLA40 35mm Chokes
Valves: Std 42.4in 36mm ex
Ignition: Std points
Pluds: B8EGV race
Sump Big wings baffled 6.5L
16 row oil cooler
Oil Pump Std
Flywheel Std 1608 small diameter lightened 5.5kg
Clutch 4 puck cerametallic std cover.
GC_35 Fiat 125T

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