75 2.5 Track Car

Started by Alfatango, January 22, 2022, 07:14:34 PM

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Hi gents. I have built a 156 track/race car as per my build thread here https://www.alfaclubvic.org.au/forum/index.php?topic=21287.0 . For me it is a huge success as I didn't realize there are other alfa nutters that care about a race car build thread.

When I was on  the track in the 156, I had a distinct thought , what if this car was rwd? Then I relaised the 75 is precisely that. I tried to buy a road registered 75 but the looks and interior are hard to get over for me for the price they ARE worth. They are great cars but I couldnt part ways with the cash and an alfetta project car came up so I will have that on historic plates. This leaves me with the space to build an angry time attack car.

Now I want to build a really angry pissed off 75 with no interior, inner doors cut out, lexan, no dashboard, no head lights or rear lights, coil over suspension and down the track a full imsa fibreglass body kit. Now from a finacial perspectice, what is a better base to work off, the 2.0 ts or 2.5l v6? A super rough 3.0l is hard to find whereas the 2.5l and 2.0 do come up. I get the 2.0 ts has the lsd and is Chain driven and is lighter at the front.

This 75 wont do anything besides time attacks on hill climbs and sprints.

So in summary, should I get a 2l or 2.5l as the base? Is the 2.5l more or less durable? How much heavier is the engine of the 2.5l over the 2.0 ts? Or does anyone have a rough 3.0l 75 that could be the base for this?


Quote from: Alfatango on January 22, 2022, 07:14:34 PM
Now I want to build a really angry pissed off 75 with no interior, inner doors cut out, lexan, no dashboard, no head lights or rear lights, coil over suspension

This 75 wont do anything besides time attacks on hill climbs and sprints.

So in summary, should I get a 2l or 2.5l as the base?
I don't think it makes much difference which you start with, because if you're building a serious time attack car you probably wouldn't be keeping the engine or transaxle anyway.


There is something that is really important to keep in mind.

The old RWD Alfa's have a narrow track width.
You can talk all about overall weights and static weight distribution numbers, but track width is a huge factor.

It will vary a bit, depending on which wheels are on the car (wheel offset), but the front of a 75 is 1,369mm. And the rear is 1,359 mm.

Strangely I couldn't find any numbers for the 156's front track width, only a mention of the different rear widths, from as low 1498mm to as high as 1509mm.
It's very, very unlikely that the rear would be wider than the front, so the front would be either side of 1500mm by a few millimetres.

Now compare that with the 75. 1500mm VS 1369mm. That's a 131mm difference! And that is MASSIVE!

There are of course loads of other differences that will all effect what is happening and why it happens, but the track width difference is a huge influence.

Just for reference sake, the E30 BMW M3, a car that was infinitely more successful in Group A Touring car racing than the Alfa 75 Evoluzione, despite having technically inferior front and rear suspension, had a track width of 1440mm, 71mm wider than the Alfa's track width.
Unfortunately too many people will gloss over this difference and just give a broad brush statement of "The M3 was 'better developed' than the 75 Evo."............. But in reality, there are tangible reasons why the M3 was a much more successful race car and track width is a very important one.
The Daily: Jumped Up Taxi (BF F6 Typhoon). Oh the torque! ;)
The Slightly More Imediate Project: Supercharged Toyota MR2.
The Long Standing Conundrum: 1990 75 V6 (Potenziata)............. What to do, what to do???

Sheldon McIntosh

Pasting something a single-seater-racing friend sent to me about 10 years ago........

I've always been keen on preparing a 116series (Alfetta) variant for the track - not because I'm fond of them as they are - but because I'm convinced I could transform them to reveal their true potential. Here is what I would do to a track 90: (just ideas)

1)  Raise the front Roll Centre. This becomes even more important if you fit the top heavy 3litre motor - you will end up with a lot of understeer as the weight of the motor rolling onto the outside front tyre causes it to break grip. The Alfettas have a roll centre about 40mm off the ground (I calculated this once by measuring the wishbone geometry). Solution: engineer something, e.g. spacer, that raises the balljoint for the upper wishbone 45mm from the top of the upright (hub assembly). This should bring the roll centre to 140mm from the ground. However the exact roll centre will depend on your chosen ride height. Basically you will end up with less lateral weight transfer onto the outside tyre, keeping more grip & load on the inside front. It will help in both short and long sweeping (Phillip Island) corners

2)  Reduce the suspension travel. Tuning the damping or spring rates doesn't really deal with the Alfettas handling woes - it skirts the real issue - which is the 2foot? of suspension travel from full droop to full bump. Choose & set your ride height, e.g 100mm from the shells floor front and rear. As you know, this is done by turning the Torsion bars on their spline at the front, and changing the spring height at the rear. Hopefully you are running shocks e.g. Konis with full service support. At the rear, at a guess I'd want the shocks to travel a distance in droop that delivers 60mm of travel at the wheel. Also 60mm of compression at the wheels in bump - giving you total wheel travel of 120mm. At the front I'm guessing I'd want 25mm of wheel travel in droop, and 50mm of wheel travel in bump - giving 75mm total wheel travel. One thing reduced travel in droop does, is keep load on the inside wheels once the suspension is topped out. This is because of the difficulty in lifting further weight off the inside of the car - since you'ld now have to generate force to lift the whole weight of the car on that wheel.
3)  Lighten the driveline. The weight of the driveshaft on an Alfetta is more than enough for easy driving - yet Alfa has coupled a great big heavy flywheel to it. I think Holden came out with Alloy driveshafts - maybe one can be retrofitted. You feel the heavy driveline in the slow engine response - e.g. when you wait and wait for the revs to go back down after an overly big blip on the throttle between down changes - or the delay in picking the revs up during the blip. This alone makes late braking a source of frustration. However, added benefits may be felt in the improved throttle response off slow corners. I felt the heavy driveline contributed to clutch wear and would recommend a twin plate set up for anything over 200bhp.

4)  Bigger wheels & lower tyres.  The 15" wheels will always hinder progress. Tyres have come so far since the 1980's - take advantage of that. I'd choose 18" wheels for the track (My cousie had them on her 75), although my other cousie had 17" on his 75, and they worked well too. With the lower profile tyres of today the overall diameter is little changed, but lateral grip is enhanced dramatically with little cost to longitudinal grip.

5)  Keep your weight low.  You have chosen a very top heavy motor. For the same reasons as you should raise the roll centre - you should keep the engine as low as possible. My ideal racing Alfetta would be dry sumped with the necessary modifications - purely to get the engine as low as possible.

Anyway, just some of my ideas, they are a car I like for their potential - but despise for their compromise in build.


If you are building a track weapon then I'd start with a TS and force feed it. It is a strong and capable engine. The 2.5 V6 sounds great but actually doesn't provide much more power than a TS. A stock TS would be underpowered I feel but with forced induction you would have enough power without the weight penalty.


Quote from: Alfatango on January 24, 2022, 07:33:18 PM
Thanks Duk. What are the options of increasing the track? Spacers? Wider wheels? If so what size spacers and wheels would you go?

Besides the evo and imsa fibre glass guards and flares, has anyone rolled the guards to get wider wheels?

This is probably a dumb idea but what about cutting the front guards horizontally and than flaring them out like drift cars?

Yes, your track width increase is limited by the body work. How you go about making the body wider probably comes down more to money and the amount of it you are prepared to part with.

As for the best way to increase the track width.
Given that this is a pure track car and would have a decently integrated, chassis reinforcing roll cage, converting the front suspension to coil springs is a no brainer.
So longer suspension arms are much better than trying to fit weird offset rims.
The steering geometry all ready has heaps of scrub radius. It's this excessive scrub radius that gives these cars their characteristic steering 'feel'.
The problem with a lot of scrub radius, is that the wheel moves in a rather large arc with steering lock. The outside wheel moves forward and the inside wheel moves rearward. And this means the wheel needs a lot of room inside the front guards for their size.
1 advantage of going with longer suspension arms, is that you can do away with the HEAVY cast steel lower arm.
And of course, while you're increasing track width, you'd be raising the front roll centre, correcting bump steer and making sure the Ackerman angle is correct.

At the rear, it's much simpler. Either ridiculous offset wheels, spacers, a combination of the 2 or custom made wheel hubs that has the mounting flange a lot further out, will do the job.

For my shed ornament (road car), 20mm front (25mm rear) hub adapters, Series 6 Mazda RX7 wheels (16x8 +50 offset), the track width is 1420mm and still fit inside the flares.
I won't use the car in that configuration, tho. Other plans are in the works and it may even include custom flares and sideskirts so I can get the track width out to the E30 M3's 1440mm.
The Daily: Jumped Up Taxi (BF F6 Typhoon). Oh the torque! ;)
The Slightly More Imediate Project: Supercharged Toyota MR2.
The Long Standing Conundrum: 1990 75 V6 (Potenziata)............. What to do, what to do???


Quote from: Duk on January 24, 2022, 02:54:19 PM
Unfortunately too many people will gloss over this difference and just give a broad brush statement of "The M3 was 'better developed' than the 75 Evo."............. But in reality, there are tangible reasons why the M3 was a much more successful race car and track width is a very important one.

The M3 was purpose built to win the then-new Group A Touring Car series. The Alfa 75 Evoluzione was a parts bin special built on a 1970's vehicle architecture. Had it been homologated with the larger Garret T4 turbocharger I'm sure it would have been more competitive but still an also ran against the all powerful M3's.
2012 Giulietta QV Manual
1982 GTV6 3L fast road build

2002 156 2.5V6 Manual
2012 159 2.4JTDm Sportwagon
1974 105 2000 GTV with a 1750 rear half...that was a shame!


Nice! I look forward to seeing your progress.
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GT . 3.2 V6 . Q2 . Kyalami Black - Red
75 . 3.0 V6 . Alfa Red - Grey

Sheldon McIntosh

You're gonna be needing this website......    https://alfagtv6.com/phpBB3/

Back when I did a similar thing to my 90, I changed my front brakes for the common (at the time) Volvo upgrade.  Especially if you're going to put in a 3.0, I wouldn't even bother with the standard brakes, they're pretty average on track, no matter what you do to them.  With the Volvo calipers and 164 rotors, I could do over an hour on track with no fade.  I don't know if they're as easily available anymore, of if there is a better option around now. 

Good luck with it all, with the mods you're thinking of, they're a great thing to drive, I loved mine. 

While you have the engine out, get the steering rack "manualised". 

Also look at the knuckle risers.

Think about seam-welding the engine bay, and definitely put in a cage.  I was running my 90 on 32mm torsion bars, on slicks, with no cage or reinforcing, and I was starting to tear the sheet-metal in the engine bay. 

I have a 6-point rollcage I want to get rid off if you're interested.  It's a bolt-in, came out of an Alfetta, but was apparently measured up for a 75 as well.  You're welcome to take it away, and just pay me for it if it fits, and if you want it.  I would get it welded in if it were me, but should still be a lot cheaper than a custom made cage. 

Good luck mate.


The car will run without it but make sure you plug all connections. Otherwise you will get a vacuum leak in the engine and a petrol smell every time you stop anywhere. Personally, given the relatively small weight for it I'd keep it installed. It doesn't hurt your power generation and the engine will be slightly smoother at partial throttle as the ECU is expecting some fumes to come from it.


I recall reading somewhere that removing the spare wheel well and just covering with a flat plate disturbed the air flow at high speeds and the better solution was to rebuild the wheel well. I can't remember where but it was a respectable source or I wouldn't have remembered it! Also don't remember how fast before it became a problem but it was regarding either 116 or 105 Alfas so can't have been going that fast... ;D


That article was crap.

The ES30's front suspension got coilsprings instead of torsion bars, spherical bearings for the caster arm chassis mounts and slightly taller uprights/spindles to change the front roll centre height and camber curve characteristics. They still used the heavy cast steel lower control arms, with the splined bosses for the torsion bars and the top control arms were basically the same, except the opening was made larger to fit around the coil spring.
The 75 and all of the transaxle chassis Alfa's have 'double wishbone' front suspension.

"To make the race-spec suspension more usable in real life, the engineering team installed hydraulically-adjustable Koni dampers, making the ride height around 2 inches higher in seconds at the click of a button on the center console."

This is done for ground clearance only.
Without knowing exactly how those Koni's work, my guess is that they use an additional hydraulic cylinder, that works independently of the damper itself, to lift the car.

"more aggressive camshaft, new intake..........."

The plenum chamber is the same as the 3 litre plenum chamber. With only minor changes for external ports and crap that the J-Jetronic engine used, but weren't needed on the Motronic run engines.
Same said for the inlet runners.
Maybe they put some actual effort into the internal finish of the inlet runners for these cars, because the factory finish in the runners on my Potenziata were terrible (undersized compared to the inlet ports (which are undersized and poorly produced) with sh!t port matching).
According Jim K, the camshafts were the same used in the Motronic run Potenziata, which are different to the earlier L-Jetronic engines, but they are hardly aggressive.
Jim K has said over the years and in his book, compared to the Potenziata engine, the ES30 engine has some more compression ratio (10 or maybe 10.5:1 rather than the 9.5:1 in the Potenziata engine) and the tubular extractors. Which aren't really anything to write home about.
And the ECU is tuned to suit.

"When pushed to its cornering limit, the SZ could withstand up to 1.1 lateral Gs. With newer tire compounds, the SZ could reportedly handle up to 1.4 G........"

This has been written over and over and I believed appropriately questioned over and over.
"up to 1.1 lateral G's".
Spike and instantaneous measurements are not the same as constant numbers. Does make for more dramatic reading, though.
And as for 1.4 G's on newer tyres............. Sure.  ::)

The chassis was structurally reinforced with additional box sections and gussets to better withstand the front suspension forces being put into the chassis through the top damper mounts, rather than through the bottom control arm mounts.
I doubt that the bonded on fiberglass body changed much if any of the cars torsional rigidity.
Especially at the front, where the chassis needs the most improvements. The bonnet doesn't reinforce the chassis and neither does the bumper bar or the front guards.
That's not to say that fiberglass isn't strong. Proper woven fiberglass cloth is very strong and so are the adhesives that are used with it. But the majority of the actual chassis is fundamentally the same and the exterior panels much more superficial than structural.
And those claims about ground effects body work............... Yeah right.  ::)
The Daily: Jumped Up Taxi (BF F6 Typhoon). Oh the torque! ;)
The Slightly More Imediate Project: Supercharged Toyota MR2.
The Long Standing Conundrum: 1990 75 V6 (Potenziata)............. What to do, what to do???


"Rats Nest Wiring Syndrome?"  ;)
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Quote from: Alfatango on April 19, 2022, 07:26:22 PM
I can see why people don't do bigger wheels on these cars. It's like they did the wheel arches as an after thought. These are 195 or 205 15s and can barely fit.
Getting the right offset is key.  225/50's is perfectly doable with standard bodywork.
14 Alfa's since 1977. 
Currently 1973 GTV 2000, 2020 911 C2S MT, 2021 Mercedes GLE350, 2023 Polestar 2 LRDM
Gone......far too many to list


I had Ronals on my 75 for a while (15x7s) with 205/50/15 rubber and it scrubbed badly. The front any where near full lock especially if on a bump. Altering steering geometry helped but never solved the problem. This was mainly the front and rear of the skirt/bumper. This was with standard road height. I've since gone down to 195/55/15 and no issues whatsoever.

I moved the Ronals over to my GTV (which is low) and no issues either.