Poll

how do i get more power from my 75?

modify the 2.5L?
2 (28.6%)
drop a 3.0L 24v in?
5 (71.40000000000001%)

Total Members Voted: 7

Author Topic: 3.0L 24v for 75?  (Read 8885 times)

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4mycar75

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3.0L 24v for 75?
« on: June 27, 2008, 09:45:34 AM »
hi all.
im new to alfas, and im wanting a bit more power from my 75. i dont know whether to modify the 2.5L or drop a 3.0L 24v in it. and how hard it would be to locate a 3.0L 24v. whats involved in the conversion? is it just engine mounts?  ive seen some 75s with 24v and they just sound and go incredible so im kinda leaning towards that idea. im also wondering where i could get an LSD from as ive been told the 2.5L manual 75 was the only 75 that didnt get an LSD which is what i have, bummer. oh and did the twin spark have longer gears?

im just setting some goals for a long term project so any help would be great.
thanks heaps

branko.gt

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Re: 3.0L 24v for 75?
« Reply #1 on: June 27, 2008, 11:23:28 AM »
i know this is not really what you asked but the cheapest way to get more power from 75 is to get potenziata. it is not 24v but it is 3.0l and it had appropriate LSD. for track you would still prefer TS gearbox but for all else this is the way to go.

No engine replacement, no transaxle replacement ....

funny enough,  Phil is selling his http://www.alfaclubvic.org.au/component/option,com_smf/Itemid,68/topic,1535.0/

Scott Farquharson

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Re: 3.0L 24v for 75?
« Reply #2 on: June 27, 2008, 12:44:17 PM »
Of course how much power do you want and what do you want to do with it?  This decision for a race/track car vs a road car may well be very different. 

A standard (and new) 24v was about 165kw compared with around 120kw for your 2.5L 12v and around 138kw for the 3.0L 12v.  To give some perspective a Group A race 2.5L 12v only ever made around 185 - 195kw and would be basically undrivable on the road.

Now you do have a number of options.....firstly going to 24v can be done but is a bit of work and is expensive.  2nd hand 24v's are around $4-5k plus you will need your 2.5L to donate some components like the sump and plenum etc and then you have to fit it.   24v's are not exactly easy to find - specialist alfa wreckers or find a 164 24v being wrecked.  You could also try to source one in europe or Hong Kong.  As I said a standard motor is about 165kw, add an autronic ECU and headers and some dyno time and that will give you closer to 190-200kw and still be very very drivable.  Hugh Harrision (9720 4442) has done a number of these conversions including a previous GTV6 of mine and Victor Lee's yellow GTV6, both with excellent results.

Second, is to fit a 3.0L 12v or just buy Phil's 3.0L.  Not as much grunt as the 24v but buying Phil's would be easier and it is a pretty good original example.  Fitting a 3.0L is easier than a 24v cos they are basically the same as the 2.5L.

Both the 3.0L and 2.5L 12v can be modified with of course the 3.0L just giving a bit more power than the 2.5L.  Typically you would do cams, ECU (say an Autronic) headers/exhaust and head porting to start with and then if you want more, hi-comp pistons. There are also "kits" available to increase capacity.  Most of this stuff is off the shelf from Vin at PACE (9844 0147) or from overseas.

Of course the engine is only part of the equation - you will need a twin spark gearbox with LSD and don't forget brakes and suspension.

Good Luck.
Scott Farquharson
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4mycar75

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Re: 3.0L 24v for 75?
« Reply #3 on: June 27, 2008, 03:16:34 PM »
thanks guys. great help.
i still want it for a road car but with plenty of power so that i could take it on the track every now and then, and it seems like the 24v is the way to go, given its good drivability. is that 190-200kW at the crank? if so, what could i expect at the wheels? it also seems like the 24v has a higher potential for further modifications and power increases which is very appealing to me.
should i be looking at the engine first or brakes and suspension first?
id rather do up the 75 i have now coz its been in the family for a while and its kinda been 'passed down' to me now and ive become a bit attatched. childish i know, but i love it.

cheers

Scott Farquharson

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Re: 3.0L 24v for 75?
« Reply #4 on: June 27, 2008, 05:02:01 PM »
A 24v with autronic and headers will give around 165 to 180 kw at the wheels.  Yes a 24v has much greater potential for improvement but at a much higher cost.

If you are going to the track and are new to the sport then definitely do the suspension and brakes first, in fact, do nothing first, run in the AROCA standard class first, get used top the car and the circuits, then look at the modified class regs and plan what you will do.  Suspension, brakes and tyres are always before power.  All the suspension stuff you need for these cars is available off the shelf, again try Hugh from Monza's or one of the other club sponsors.

Plenty of people are running 75's so there is lots of experience to learn from.  Go to a track day and talk to the guys running 75's.  The path to building a good V6 transaxle car (75, 90, GTV6) is well worn - talk to other competitors and guys like Hugh - they have done it all before.
Scott Farquharson
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Sheldon McIntosh

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Re: 3.0L 24v for 75?
« Reply #5 on: June 28, 2008, 12:08:08 PM »
DEFINITELY brakes and suspension first, then an LSD before a big hike in power.  You'll be surprised how much you can get out of the available power just by doing the aforementioned, and I certainly wouldn't want to drive a 24V with standard 75 brakes.  A 24V without an LSD would only be fast in a straight line, and that's not what Alfas are about.

The TS LSD has shorter gears, and I believe the 3.0 LSD has the same gearing as the 2.5.

If you know your way around a spanner and have a few days spare, check out this link for slightly more power and lots more reliability from your 2.5.
http://www.hiperformancestore.com/Ljetronic.htm

4mycar75

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Re: 3.0L 24v for 75?
« Reply #6 on: July 01, 2008, 12:03:24 PM »
yeh now that i think about it its pretty logical to do brakes and suspension first otherwise there wouldnt be much point in upping the power unless i can control it.

in that case, what suspension, brakes and tires would you guys recommend? worth doin the torsion bars?

thanks

Dna Dave

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Re: 3.0L 24v for 75?
« Reply #7 on: July 01, 2008, 02:14:16 PM »
Hi,

I got a 24V in my GTV6 with coilovers, work very well, I got a spare set made up, call me if interested

David 0419 624 193
1984 GTV6 3.0L South Africian (charcoal)
1991 Alfa 75 Potenziata
1985 GTV6 South Africian Rep (white) 3.2L gta motor
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Past,

Not that many 😜

Scott Farquharson

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Re: 3.0L 24v for 75?
« Reply #8 on: July 01, 2008, 04:45:29 PM »
Again the suspension setup for the track in these cars is pretty well worn path, typically koni yellows, at least 28mm torsion bars, bigger rear springs and front sway bar, rear sway bar, front roll centre riser, around 3-4 degrees neg camber front, di dion tube can be modified to provide rear neg camber (needs to come out and be put in a jig), all can be obtained off the shelf (except the di dion bending) and fitted yourself (although the torsion bars are a pain without a hoist) or you can go to one of the sponsors buy them there and have them fitted.

The coil-overs offered may also be an option, but of course is a little less conventional.  Not sure what the cost difference may be either.
Scott Farquharson
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Southern75

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Re: 3.0L 24v for 75?
« Reply #9 on: July 15, 2008, 08:21:13 PM »
What do you guys actually do as far as brakes in the 75 ... mine is stock 2.5l but some minor tweaks + exhaust but have 28mm torsion bars, 220lb springs all polyurethane bushed and TS gearbox with a shimmed up diff.

The problem is it doesn't really stop ... Brakes need to be done!

BTW the 3.0 75 with LSD is a far taller ratio than the 2.5 .... i changed to the TS box and there was little or no difference to the gearing as far as highway driving. Yes first is taller and there is less gap 2nd through to 5th but i think that i cruise at 110 about 100rpm lower than with the original box.... that's it.

You can fit a automatic 75 diff the the 2.5 litre box to get an LSD but the gearing gaps are frustrating whereas this is not an issue with the TS box.

My advice... TS box is the easy option.

A bloke i know did a 24v in a 75 and he ditched the standard box in favour of a TS box ...

If i had the money i would go the 24v ... however there is supercharger kits available from the US ... this could be an interesting option as you could land one for the 12v engine for about 4.5 to 5 k plus fitting.

They sound well researched and comprehensive but may be asking for trouble.

As Scott has said the 24v is a nice flexible option but i think you can get out of it a bit cheaper than he has suggested as there has been number of 24v engines with ecu surface in Sydney for 2.5 to 3.5.
Also ... my friend did one in a GTV6 with the fly by wire throttle .. these engines are becomming more and more popular as a result of P platers wrapping GTA's and 99 and newer GTV6's around heavy objects.

Find out how much it will/can cost to install ... that's my advice
Rust, nah that's not rust .... its iron oxide!!!

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1977 Alfasud ti (race)
1980 Alfasud ti (race)
1987 75 V6 (toy)
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Sheldon McIntosh

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Re: 3.0L 24v for 75?
« Reply #10 on: July 16, 2008, 10:21:55 PM »
di dion tube can be modified to provide rear neg camber (needs to come out and be put in a jig)

Is there much benefit from this mod Scott?

What do you guys actually do as far as brakes in the 75 ... mine is stock 2.5l but some minor tweaks + exhaust but have 28mm torsion bars, 220lb springs all polyurethane bushed and TS gearbox with a shimmed up diff.

The problem is it doesn't really stop ... Brakes need to be done!

I've changed to Volvo calipers and braided lines on the front, but still with standard rotors.  The Volvos are 4 pot and bolt straight on (off the 200 series Volvo I think).  Unfortunately they don't sweep the whole rotor (miss about 10mm) but 156 rotors can be adapted to fit and match up to the calipers.  Even with the standard rotors the difference is very noticeable.  I've had no complaints with my brakes since putting them on, and you get a better range of pads to choose from too. Highly recommended. 

I've got a 90 with standard suspension, and the thing just about buries it's nose when I brake hard nowadays.  I nearly ran into the back of a clubman at our 6-hour I was braking so much later than him.

alfagtv58

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Re: 3.0L 24v for 75?
« Reply #11 on: July 17, 2008, 09:26:24 AM »
di dion tube can be modified to provide rear neg camber (needs to come out and be put in a jig)

Is there much benefit from this mod Scott?



Yes, there sure is.  Handling improves due to the tyre contact patch being much larger when cornering.  And the other benefit is the tyres wont be constantly scuffed over just one edge, they wear much more consistently.

But we are talking about a 90 here....which leans more than a channel 9 journo during election time.....so you would probably need about 15 degrees.
« Last Edit: July 17, 2008, 09:36:26 AM by Phil Baskett »
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Sheldon McIntosh

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Re: 3.0L 24v for 75?
« Reply #12 on: July 17, 2008, 03:15:37 PM »
I understand the concept of negative camber, the reason I asked is that I thought the whole raison d'etre of the dedion on the transaxle cars was that it always kept the rear tyres flat on the road, no matter what the roll angle, as illustrated.

I find my rear tyres wear reasonably evenly.  The fronts however.....

Scott Farquharson

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Re: 3.0L 24v for 75?
« Reply #13 on: July 17, 2008, 05:13:14 PM »
Yes, and yes.   The idea of the de dion tube is to keep the wheel vertical (no camber change) as the wheel goes up and down, unlike the wishbone setup on the front where the camber changes significantly throughout the wheel travel, however you do get some/slight positive camber change on the outside wheel when the inside wheel is compressed independantly (ie the inside wheel hits a bump)

But it is not just about the wheel being vertical, you also have tyre flex/weight transfer as well - you have all those forces in the middle of the wheel pushing the wheel out and down and the contact patch at the end of a short rubber lever.

So all in all 1.5-2 degrees of neg on the de dion is a good thing - makes sure you have the best possible contact patch on the road.
« Last Edit: July 17, 2008, 05:15:29 PM by Scott Farquharson »
Scott Farquharson
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