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post #1 of 9 (permalink) Old 06-17-2003, 02:15 AM Thread Starter
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GTAm questions

Okay I have been thinking hard about a race car related project once I finish restoring my 1750 GTV to concours condition. And while I want this car to be one of the few original standard ones left I also want to return to the race track, but not obviously in this car.

Thus I have been thinking of building my own clubmans racing car again, maybe mid-engined this time and if rules allow maybe even with an alloy monocoque ... OR I have also been thinking of creating a replica of a works GTAm out of a shell that nobody wants.

How much does a GTAm weigh? I know they were built on the 1750 STEEL shell and thus not as light as the alloy GTAs (which I think were as light as 600kg's).

To be any fun and serious enough to be really competitive Ii think we need to be as close as possible to 400 hp per 1000 kg's (like my last clubmans car).

Thus with a 2ltr twin plug engine you maybe able to squeaze close to 250 hp (I have seen a reliable 210 hp with single plug engine), thus I need a car that only weighs 625 kg's.

The 105 series is not a heavy car, but I think if they were still all steel then you would struggle to get below 700 kg's. Thus were the guards fibre glass. I assume the bonnet, doors and boot were all fibre glass, and windows plastic, but you have to add the weight of a roll cage. During the shell restoration process you could lighten the shell heaps ...

Does anybody have the specification sheet of a works GTAm?

Pete
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post #2 of 9 (permalink) Old 06-17-2003, 02:51 AM
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For those of us on this side of the pond.

600 Kg. = 1323 Lbs.
1000 Kg. = 2205 Lbs.
625 Kg. = 1378 Lbs.
700 Kg. = 1543 Lbs.

(I'm just funnin' about)

Kai Schorr
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post #3 of 9 (permalink) Old 06-17-2003, 06:32 PM Thread Starter
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Found excellent site for GTAm

From http://www.mid-atlantic-aroc.org/Racing/GTAm.htm

Origins
The GTAm may have originated from a seemingly small change in the FIA’s rules for international touring car competition that became effective January 1, 1970. The GTAm’s predecessor, the brilliant Giulia Sprint GTA, had dominated international Touring Car racing in the late 1960s, earning Alfa Romeo and its drivers no less than three European Championships, plus the first-ever Trans-Am Championship, between 1966 and 1969.
For 1970, however, the FIA’s rules defining Touring cars were modified to require more space for rear seat passengers. Although the change in the dimensions was not large, it was enough to disqualify the GTA from competing in the Group 2 Touring class where it had been so successful in the past. Group 1 was essentially a showroom stock class for unmodified sedans, or touring cars, Group 2 was for race-prepared touring cars, Groups 3 and 4 were for "Grand Touring" cars (essentially two-seaters) and Groups 5 and above were for prototypes and formula cars. The GTA was reclassified to Group 4, for limited-production Grand Touring cars. The same fate incidentally befell one of the GTA’s toughest opponents in past years, the Porsche 911.
In January, 1970, the factory announced a list of incremental changes in the current 1750 model line, including both obvious ones like a dual braking system and suspended pedals, and more subtle ones, like "enlarged and improved" rear passenger accommodations for the 1750 GTV. Although the difference in the GTV’s rear accommodations is not evident from a casual inspection, the rear parcel shelf and some of the sheet metal members in the rear seat area were reshaped to gain an inch or two of leg room for the rear passengers. Although there is no direct evidence that the changes were made to further racing interests, the resulting rear passenger space was large enough to allow the 1750 GTV to be classed as a Touring car for 1970, while the smaller GTA was reclassified as a two-seater.
Development and Construction
Private entrants had started racing the 1750 GTV in the Group 1 unmodified class from its introduction, and the car achieved a respectable record. In April, 1969, the factory homologated the GTV as a Group 2 touring car, opening the way to competition on higher, and more visible, levels. On the technical front, several innovations introduced in 1968 and 1969 suggest that Autodelta, the Alfa Romeo subsidiary that ran the factory racing effort, had already begun the development of a new racing car to replace the GTA by that time. Autodelta may have prepared one or more GTAs equipped with 1750 engines bored out to 1985 cc for private owners as early as 1968. The new 2-liter engine appeared definitively in November, 1969 in a pair of GTAs entered in the Tour of Corsica. This new engine had the 88.5 mm stroke of the production "1750" engine, but a larger bore of 84.5 mm, giving a total displacement of 1985 cc and yielding 208 HP. The larger bore was achieved by fitting the 1750 block with a unique set of "monosleeve" liners with all four cylinders cast in one unit. The 2 liter engine also featured a new cylinder head with twin-plug ignition like the GTA, but a 45-degree valve angle instead of the usual 80 degrees, and had a mechanical fuel injection system made by Lucas.
The development of the GTAm was essentially a process of improving the production GTV to compete more effectively. The GTAm was homologated for FIA-sanctioned international competition in October, 1969. The strong connection to the 1750 GTV is immediately obvious from the homologation document (No. 1576): the photo on the first page shows a standard, roadgoing 1750 coupe, complete with hubcaps and bumpers. The more remarkable feature is that the chassis and engine number shown are those of the US model 1750 GTV, tipo 105.51.
Period factory publications made it clear that the name was a reference to the car’s American connections: in the Jaunary, 1970 issue of Il Quadrifoglio (v.5, no. 14, pp. 68-69) the full name listed in the text is "1750 GT America." Nevertheless, there has been considerable confusion concerning the meaning of the name GTAm, with some authoritative sources suggesting that it stood for GTA "maggiorata" (enlarged) or that "Am" was an abbreviation for "alessagio maggiorato" (enlarged bore).
Adding to the confusion was a name change at the beginning of the 1971 racing season. The original full name of the GTAm was, logically enough, "1750 GTAm" in recognition of its evolution from the production 1750 GTV. In 1971, the name was changed to 2000 GTAm in anticipation of Alfa Romeo’s new 2 liter model line. It was a name change pure and simple, however. There was no change in the cars: every known GTAm was derived from a production 1750, and all of them had 2 liter engines.
In choosing the US model as the basis for the new race car, Autodelta apparently wanted to ensure with certainty that they would be able to equip it with fuel injection. To qualify for Group 2, at least 1000 identically-equipped examples had to be produced for sale to the public in a one-year period, but that requirement was easily met by production of the SPICA injected 1750 GTV for the US market. This approach to meeting minimum production quotas was distinctly different from the one that had been taken with the GTA. While the Giulia Sprint GTA was a distinct model with its own number (tipo 105.32) and was available for purchase by the public, the GTAm was nothing more than a GTV modified with homologated factory parts. In explaining the GTAm to American enthusiasts, Don Black wrote in Alfa Romeo, Inc’s Competition Advisory Service:
The "GTAm" is the US version of the 1750 G.T. Veloce [Type 105.51] sold only in the USA. At the time the homologation documents were prepared, it was known as the G.T. America and eventually shortened to "GTAm" ...The differences [between the 1750 GT Veloce and the GTAm] are only options. To illustrate; a "GTAm" without options is a 1750 G.T. Veloce–USA.
Visually, the GTAm is distinguished from other racing 105 coupes by the combination of the lovely 1750 grille with riveted-on, wide plastic fender flares. The flares accommodated meaty tires carried on 8 to 10 x 13 inch wheels identical to the ones used on the tipo 33 sports racer. The definitive mechanical element of the GTAm is the fuel-injected 1985 cc monosleeve engine with the narrow-angle, twin-plug head. Most other special mechanical assemblies were carried over from the GTA, including the gearbox and differential, the Autodelta sliding block for locating the rear axle, and the GTA’s other special suspension parts.
Because the GTAm was a pure race car, its specifications seem to have varied from car to car. Autodelta would have prepared the works team cars to conform to the rules prevailing at the time, and most likely modified the cars as needed for particular events. Mechanical fuel injection systems by both SPICA and Lucas were used, for example. The application of lightweight body panels also varied considerably. GTAms were constructed from standard, steel GTV body shells, but some examples were fitted with aluminum or plastic doors, hoods, or trunk lids, which were listed as options in the homologation document. These lightweight pieces were used less frequently as time went by, however. Changes in the Group 2 rules first raised the GTAm’s minimum allowable weight, reducing the advantage of using lightweight panels, and then for the 1972 season, alternative lightweight body assemblies were disallowed entirely.
Even the GTAm’s color scheme was variable. While the works GTAs are remembered in the classic Italian red livery, factory GTAms raced not only in the well-known red, but in such diverse colors as gray, white, and "beige cava."
As a consequence of the fact that the GTAm never had its own model number, it is difficult to be certain how many cars were actually built. In Alfa Romeo: All the Cars from 1910, Luigi Fusi claims that around 40 examples were produced. The number of cars that can actually be documented is much smaller. Later works on the racing coupes list by Adriaansens and Tabucchi list 14-15 chassis numbers of US model 1750 GTV known to have been converted to GTAms by Autodelta. The number of GTAms campaigned by the factory team could not have been larger than this, but Adriaansens lists only 8 cars with verified histories as works team cars. The remaining 7 may have been prepared for private owners. Tabucchi also lists two additional VINs of European-model GTVs that Autodelta transformed into GTAms for a private racing team. Similar cars prepared for private clients may have made up the remainder of the 40 GTAms Fusi mentions. The total number of GTAm-like racing cars could have been still larger. Although the GTAm was not listed in Alfa’s catalog, the special competition parts used in it were, so anyone with a GTV could have built their own.

Pete
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post #4 of 9 (permalink) Old 06-17-2003, 07:22 PM Thread Starter
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Hmmm

From what I have read if I bought a USA (105.51) spec 1750 GTV body shell and created special liners and pistons for a 84.5mm bore AND used the Alfa 75 twin plug cylinder head I would have a GTAm. Note it is not the same engine dimensions as the 2000 GTV which has a 84mm bore and is 1962cc compared to the GTAm of 1985cc.

I assume the production twin plug head used in Alfa 75s has the narrower valve included angle of 45 degrees instead of the GTAs angle of 80 degrees. Can anybody confirm this?

Also the doors, boot and guard extensions can be plastic ... but that is all. Thus it would still be heavier than a GTA, surely?

They also talk about only 208 hp, which is interesting as I know of single plug 2ltr engines producing these numbers ... maybe we have learnt something in the last 30 years

Pete
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post #5 of 9 (permalink) Old 06-18-2003, 07:13 AM
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PSK,

I have a Alfa performance catalog that lists
all the parts for a GTAM, and their weights,
I would be glad to photocopy it and mail you
a copy.

E-mail me you address if you are intersted.
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1971 GTV ongoing "restoration" project (Rice Conversion)
1978 Spider sold in 1996
1962 Guilietta Spider sold looong ago
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post #6 of 9 (permalink) Old 01-30-2019, 03:47 AM
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Cool

Quote:
Originally Posted by PSk View Post
From http://www.mid-atlantic-aroc.org/Racing/GTAm.htm

Origins
The GTAm may have originated from a seemingly small change in the FIA’s rules for international touring car competition that became effective January 1, 1970. The GTAm’s predecessor, the brilliant Giulia Sprint GTA, had dominated international Touring Car racing in the late 1960s, earning Alfa Romeo and its drivers no less than three European Championships, plus the first-ever Trans-Am Championship, between 1966 and 1969.
For 1970, however, the FIA’s rules defining Touring cars were modified to require more space for rear seat passengers. Although the change in the dimensions was not large, it was enough to disqualify the GTA from competing in the Group 2 Touring class where it had been so successful in the past. Group 1 was essentially a showroom stock class for unmodified sedans, or touring cars, Group 2 was for race-prepared touring cars, Groups 3 and 4 were for "Grand Touring" cars (essentially two-seaters) and Groups 5 and above were for prototypes and formula cars. The GTA was reclassified to Group 4, for limited-production Grand Touring cars. The same fate incidentally befell one of the GTA’s toughest opponents in past years, the Porsche 911.
In January, 1970, the factory announced a list of incremental changes in the current 1750 model line, including both obvious ones like a dual braking system and suspended pedals, and more subtle ones, like "enlarged and improved" rear passenger accommodations for the 1750 GTV. Although the difference in the GTV’s rear accommodations is not evident from a casual inspection, the rear parcel shelf and some of the sheet metal members in the rear seat area were reshaped to gain an inch or two of leg room for the rear passengers. Although there is no direct evidence that the changes were made to further racing interests, the resulting rear passenger space was large enough to allow the 1750 GTV to be classed as a Touring car for 1970, while the smaller GTA was reclassified as a two-seater.
Development and Construction
Private entrants had started racing the 1750 GTV in the Group 1 unmodified class from its introduction, and the car achieved a respectable record. In April, 1969, the factory homologated the GTV as a Group 2 touring car, opening the way to competition on higher, and more visible, levels. On the technical front, several innovations introduced in 1968 and 1969 suggest that Autodelta, the Alfa Romeo subsidiary that ran the factory racing effort, had already begun the development of a new racing car to replace the GTA by that time. Autodelta may have prepared one or more GTAs equipped with 1750 engines bored out to 1985 cc for private owners as early as 1968. The new 2-liter engine appeared definitively in November, 1969 in a pair of GTAs entered in the Tour of Corsica. This new engine had the 88.5 mm stroke of the production "1750" engine, but a larger bore of 84.5 mm, giving a total displacement of 1985 cc and yielding 208 HP. The larger bore was achieved by fitting the 1750 block with a unique set of "monosleeve" liners with all four cylinders cast in one unit. The 2 liter engine also featured a new cylinder head with twin-plug ignition like the GTA, but a 45-degree valve angle instead of the usual 80 degrees, and had a mechanical fuel injection system made by Lucas.
The development of the GTAm was essentially a process of improving the production GTV to compete more effectively. The GTAm was homologated for FIA-sanctioned international competition in October, 1969. The strong connection to the 1750 GTV is immediately obvious from the homologation document (No. 1576): the photo on the first page shows a standard, roadgoing 1750 coupe, complete with hubcaps and bumpers. The more remarkable feature is that the chassis and engine number shown are those of the US model 1750 GTV, tipo 105.51.
Period factory publications made it clear that the name was a reference to the car’s American connections: in the Jaunary, 1970 issue of Il Quadrifoglio (v.5, no. 14, pp. 68-69) the full name listed in the text is "1750 GT America." Nevertheless, there has been considerable confusion concerning the meaning of the name GTAm, with some authoritative sources suggesting that it stood for GTA "maggiorata" (enlarged) or that "Am" was an abbreviation for "alessagio maggiorato" (enlarged bore).
Adding to the confusion was a name change at the beginning of the 1971 racing season. The original full name of the GTAm was, logically enough, "1750 GTAm" in recognition of its evolution from the production 1750 GTV. In 1971, the name was changed to 2000 GTAm in anticipation of Alfa Romeo’s new 2 liter model line. It was a name change pure and simple, however. There was no change in the cars: every known GTAm was derived from a production 1750, and all of them had 2 liter engines.
In choosing the US model as the basis for the new race car, Autodelta apparently wanted to ensure with certainty that they would be able to equip it with fuel injection. To qualify for Group 2, at least 1000 identically-equipped examples had to be produced for sale to the public in a one-year period, but that requirement was easily met by production of the SPICA injected 1750 GTV for the US market. This approach to meeting minimum production quotas was distinctly different from the one that had been taken with the GTA. While the Giulia Sprint GTA was a distinct model with its own number (tipo 105.32) and was available for purchase by the public, the GTAm was nothing more than a GTV modified with homologated factory parts. In explaining the GTAm to American enthusiasts, Don Black wrote in Alfa Romeo, Inc’s Competition Advisory Service:
The "GTAm" is the US version of the 1750 G.T. Veloce [Type 105.51] sold only in the USA. At the time the homologation documents were prepared, it was known as the G.T. America and eventually shortened to "GTAm" ...The differences [between the 1750 GT Veloce and the GTAm] are only options. To illustrate; a "GTAm" without options is a 1750 G.T. Veloce–USA.
Visually, the GTAm is distinguished from other racing 105 coupes by the combination of the lovely 1750 grille with riveted-on, wide plastic fender flares. The flares accommodated meaty tires carried on 8 to 10 x 13 inch wheels identical to the ones used on the tipo 33 sports racer. The definitive mechanical element of the GTAm is the fuel-injected 1985 cc monosleeve engine with the narrow-angle, twin-plug head. Most other special mechanical assemblies were carried over from the GTA, including the gearbox and differential, the Autodelta sliding block for locating the rear axle, and the GTA’s other special suspension parts.
Because the GTAm was a pure race car, its specifications seem to have varied from car to car. Autodelta would have prepared the works team cars to conform to the rules prevailing at the time, and most likely modified the cars as needed for particular events. Mechanical fuel injection systems by both SPICA and Lucas were used, for example. The application of lightweight body panels also varied considerably. GTAms were constructed from standard, steel GTV body shells, but some examples were fitted with aluminum or plastic doors, hoods, or trunk lids, which were listed as options in the homologation document. These lightweight pieces were used less frequently as time went by, however. Changes in the Group 2 rules first raised the GTAm’s minimum allowable weight, reducing the advantage of using lightweight panels, and then for the 1972 season, alternative lightweight body assemblies were disallowed entirely.
Even the GTAm’s color scheme was variable. While the works GTAs are remembered in the classic Italian red livery, factory GTAms raced not only in the well-known red, but in such diverse colors as gray, white, and "beige cava."
As a consequence of the fact that the GTAm never had its own model number, it is difficult to be certain how many cars were actually built. In Alfa Romeo: All the Cars from 1910, Luigi Fusi claims that around 40 examples were produced. The number of cars that can actually be documented is much smaller. Later works on the racing coupes list by Adriaansens and Tabucchi list 14-15 chassis numbers of US model 1750 GTV known to have been converted to GTAms by Autodelta. The number of GTAms campaigned by the factory team could not have been larger than this, but Adriaansens lists only 8 cars with verified histories as works team cars. The remaining 7 may have been prepared for private owners. Tabucchi also lists two additional VINs of European-model GTVs that Autodelta transformed into GTAms for a private racing team. Similar cars prepared for private clients may have made up the remainder of the 40 GTAms Fusi mentions. The total number of GTAm-like racing cars could have been still larger. Although the GTAm was not listed in Alfa’s catalog, the special competition parts used in it were, so anyone with a GTV could have built their own.

Pete
Hi Pete,
Well, what can I say?
I will say in 1970/1 the GTV 1750 could run alloy doors and bootlid.
That is a good point all LHD US 1970 GTV 1750 were homoligated as GTAm., so based on FIA rules 1970 page 30
h) Recognition forms: all cars recognized by the FIA shall be the subject of a descriptive form called recognition form on which shall be entered all data enabling Identification of the said model.
.
.
'Whenever the scrutinizing of a car shows the complete compliance of it with its recognition form, in as much as is required for the group in which it is admitted, there
is no need to worry about its year of fabrication'.

There are even race series in Europe today that cater for these cars, just imagine more of these cars on the race track.
I think one even came to Australia for a race meet?
Cheers
Steve

Last edited by Steve105; 01-30-2019 at 12:39 PM.
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post #7 of 9 (permalink) Old 01-30-2019, 04:15 AM
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My wide body stepfront racecar has: complete frontclip in polyester, doors en trunklid too, light safetytank, lexan windows. light racing shocks, lightened suspension parts etc etc. We get it at 875 kg with about 20 ltrs of fuel .
With 8x15 wheels. Maybe something to gain there but will need very expensive wheels to lower the weight maybe 8-10 kg..more simple cage will reduce too.

I think the car from Alfaholics, base steel with kevlar doors etc, light windows, simple cage but 2 seats and upholstery in (though light version) does 840kg.

App. K says a 1750 GTAm may do 930kg.

My TS engine (adapted 75 head on 155 block) does 213 hp @ 7250 . (10.6CR, 48mm ITB and EFI, from 7000-8000 at least 205 HP there)
With a bit higher CR and some other work we may reach close to 220, but with risk considering lifetime of the engine. I dont want that...

Formula GT München The formula GT testa stretta does 217 hp.
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post #8 of 9 (permalink) Old 01-30-2019, 04:20 AM
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but why do you need 400hp/1000kg?? what is the competition?
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post #9 of 9 (permalink) Old 01-30-2019, 12:21 PM
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I think cars had to run even their spare wheel, and ballast to make up the minimum weight.
here is one for sale
https://www.classicdriver.com/de/car...50/1969/561051
Cheers Steve

Last edited by Steve105; 01-30-2019 at 12:44 PM.
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