GTAm

[164QV]

Here is a link to the FIA papers # 1576 for the GTAm - at the danish racing organizations site - although they dont seem to be complete. They are at the FIA site too somewhere.

By the way, heres a good read (I think it has been mentioned several times before).

Quote:

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.

[OldAlfaGuy]

Jim K.,

Because of the continued confusion about included valve angle on different four cylinder Alfa engines, I was actually going to quote your book as a source of facts on this issue. Since you are now with us, could you please verify the valve angles as I understand them in the list below?

105 series 1300, 1600, 1779 (1750) single plug - 90 degree
GTA /GTA Jr twin plug - 90 degree
105 (and US 115) series 2000 - 80 degree
GTAm - 60 degree
TS - 46 degree

BTW, I can't wait for the latest edition of your book!

OldAlfaGuy

[Berlinista]

the whole problem is that right now, having sold my house, I'm living at my parents. The have internet through the phone line.
Do you have any idea how long it takes to post even ONE (1) picture????
In May I'll be into my nice new house, have ADSL and probably have a nice website running. All you guys will have to wait till then.
But it will be worth it......
Cheers,
Rik

[Jim K.]

From one....old Alfa guy to another!
The ooold 102 series (up to 1962) HAD 90* angle.
All 105 series (1300,1600,1750,2000,GTA,GTA Jr) have 80*angle.
GTAm, TS have 46* angle.
With this opportunity, I'd like to dispell the belief that the GTAm head is God's gift to breathing, because its not. Its a very good breathing head, but a prepared TS head with 46mm intake valves will flow better, especially if its from a 155 (they have better entry geometry).
Oh and the name, GTAm is GT America, thats where the initial homologation came from, because thats the only market the SPICA system was sold! It was the only way that Alfa could use the system, otherwise they would have to stay with carbs (and some GTAm's had carbs, as did the rally Alfettas with this engine).
The 'GTA maggiorata' claim is false, because the GTAm did not have an 'Alleggerita' body. GTAm's were steel bodied cars, with minor plastic details and they weighed 960kg.
Jim K.

[Berlinista]

See, I knew they didn't have to have injection!
Jim, one question:
Here in Holland we are running with the questio of what is better in a racing car: We use 'sleeved' heads, Ie between carbs and head we use a sleeve , designed and machined, which is fitted inside the head and manifold.
We run modified 40 mm carbs and get close to 200 Hp with serious cams (modified heads to accept them) using several different profiles, Cosworth pistons etc. I say a car is faster, notably out of corners, on 40's. Others say ' Use 45's' Top speed is better.
My reasoning is because of gas flow a 45 is slower, except on tracks with very long straights so the engine can get really 'up and running' in which situation the lower flow is negated.
However: I think a modified TS (75) engine in a 105 series DOES run better on 45's. And that even without the 155 head.
Am I right, given the above? Don't know exactly why, just based on what I see on the track..... Others say it shouldn't make a gnat's *** of difference. What say the Tuning God??
(EVERYONE involved in racing Alfa's here in Holland has your books!! Take pride!)

[Jim K.]

I do believe in God, but he's not on this planet!
This is a very difficult subject to set hard and fast rules on. It all depends on the kind of track the car is running.There is no one perfect choice. If you're running top end, 45's are better, but you should be more interested in TRANSIENT response from the engine. A 45 carb flows better than a 40, only with venturis larger than 36mm. If the track has all kinds of slow corners, smaller venturis are needed. All-out horsepower is seldom called for and someone has said a long time ago ''I'll trade 10 horses at 7000rpm for 5 horses at 3000!'. There are all kinds of calculations you can do to determine carb and venturi size, but there is no substitute for experimentation. All modern race and rally teams, simulate the various tracks and stages on the dyno, to calibrate engine parameters. I'm afraid that you have to run the same track with 40's and then with 45's to decide. There simply is no other way. Steady state dyno testing has nothing to do with driving the car! Big power numbers may look impressive, but in the track its a different story. I'm sorry I can't be more helpful than this! I've been trying to convince some racers to downgrade their cams, for others with lower power but more low rpm power-its difficult to swallow,if its your car!
Jim K.

[Berlinista]

There's that , of course. It's just that in battle for position, I think the car running 40's is on the advantage, as it can get out of a situation sooner. Actually, your story on having 5 Hp more @ 3000 than having 10 Hp more at 7500 is what I mean.
Actually, our cars will do 8600 rpm, and I have witnessed a 105 race engine @ 10000 RPM .... and survive.... (and seen 'm GOOOO at 9500 RPM
check us out on www.alfaromeochallenge.com . in Germany, we drive Cossie Drivers , M3 E30 drivers and such MAD on the ' Ring.
Do you know what I mean by a Sleeved head, by the way, do you know of that stateside?
What of the 45's on a TS engine. Given the same specs, what is the real difference in PERFOMANCE , I mean the REASON for more performance from a TS head as compared to a Nord head? Better combustion shape? Flame front(s)? Port design isn't that different, is it? I don't mean 155 heads, but ornery 75 TS heads.

[Jim K.]

As far as sleeving goes,I know that AD was doing that with the overly large ports on the GTA heads in 1968-9. The ports were too large (about 39mm!!) for the 1300/1600 engines and they pressed in copper tubes with adhesive to correct the problem by making the ports about 36-37mm. Other than that, I haven't seen this done in Alfa heads. You're not talking about Downdrafting I suppose (changing the port entry angle) as this is almost impossible due to the follower bores. The ports in the 2liter Nord are small even for the 44mm valves.If you go to 46mm or even to 47mm valves, serious porting is needed and the walls are too thin in the wrong place! The std head flows about 90cfm and with 46mm intake valve+porting you can achieve 120cfm, which, according to Superflow, is good for more than 205hp at around 7600-7800rpm. I'd be very interested to hear about a 105 head flowing more! I believe that with excellent detailing, 125 is possible, but this is the exception. Please explain this sleeving thing to me,who would want to reduce the size of the ports on a 7500+ rpm engine? (but then, they elected Bush again,so I guess everything is possible!Hahah!)
The TS head has better entry geometry, giving a more even flow velocity spread around the seat. It has evidently less shrouding and is an excellent candidate for larger valves. The shallow roof,flat piston and twin ignition all lead to more torque and higher efficiency (same power for less fuel= better BSFC). The resulting higher power is logically produced, although,I suspect we'd all be happier if AR had opted for the 16v solution instead,which they dropped to the advice of their marketing people (wanting to sentimentally link the TS to the GTA).
Jim K.

[dretceterini]

I totally agree.

When I was racing 1 liter Mini Coopers 30 years ago, the only place we could really keep up with the Abarths is on short tracks. We were down almost 15 horsepower, and they were lighter too, but they made all their power at the top end of the RPM range.

There are very few tracks on which peak HP really matters. Flexability and low end torque are more important.

[genericwood]

Quote:

Originally Posted by Jim K. All-out horsepower is seldom called for and someone has said a long time ago ''I'll trade 10 horses at 7000rpm for 5 horses at 3000!'. Jim K.

[nicke]

Look at this hood from ebay: http://cgi.ebay.com/ebaymotors/ws/eB...949457347&rd=1

Nick

[genericwood]

Quote:

Originally Posted by nicke Look at this hood from ebay: http://cgi.ebay.com/ebaymotors/ws/eB...949457347&rd=1Nick

[Berlinista]

Fiberglass and carbon: www.autochristiano.nl
Jim, port size , valve size etc are indeed enlargened. And entry angle is different. I will try to get some facts and pics through. I just build bodies, not engines. To each his own, and we all specialize in something here. Maybe some pics on www.alfaromeochallenge.com .
The tubing is so as NOT to have to do too much to the head itself. The tubes are clamped by way of a flanged cutout in the inlet plenum or what do you call it. They have a venturi so as to increase flow. They are very very thin, and each set belongs to a particular head, and are made and sold as a set.
Friday I will be at the engine builder for the series, an will take pics and sizes.
Rik

[classicalfas]

There is most of a GTAm motor for sale on Ebay.

http://cgi.ebay.com/ws/eBayISAPI.dll...133120769&rd=1

[PSk]

Quote:

Originally Posted by classicalfas There is most of a GTAm motor for sale on Ebay. http://cgi.ebay.com/ws/eBayISAPI.dll...133120769&rd=1