group 1(a) cams or how I learnt to love the grunt

[carlo rossi]

Well I finally got the courage to install the Group A(1) cams to the 2.0 GTV
I previously only installed the inlet and used a 10548 cam on the exhaust
for 2 reasons most people say this is a great combination and should be good for
around 150-155 hp and it was great and very smooth
Also its so easy to fit the inlet exhaust is harder
so Happy days OR was it?

But now that a friend lent me his shim BOx ( he is now a GOD) I had the shims to install the
the exhaust cam I spent 4 hours on the weekend to redo both cams and shim them tighter.
S
The result is in and I can say ITS a MUST DO
wow the power and sound change out of the exhaust is gruntier
and it likes to break traction constantly
this I might say is in combination with my carby jet changes ( a must read how to tune a 2ltr ) or its a waste of time
standard airbox standard exhaust and standard bottom end my dyno bum thinks there is aleast another 8 to 10hp( thats over the inlet increase with adding just the extra exh )
cant get group A cam? i hear you ask!
well Colombo and Bariani still make the copy that is close, its now called 109292 S  or AR sm2  or cb47 is the better of the 3
and alfaholics sell them as well
109  is the lift ( 10.92) 292 is deg is dur ation at 0  as opposed to stock at 9.6mm ,and the S is for Street ,not to be confused with the " C" for competition bigger duration lumpy! with the S you dont have to modify the head
straight in (if you have the magic shim box)
Rigi is doing the january DYNO day so we can see the difference
CIao I mean Zoom

[GR-124]

Sounds like a great mod. Thanks for the info CR.
hope I hear it buzzing around Newy one day.

[carlo rossi]

yeh the american guys bag these cams because they have injection
and overlap doesnt do anyhing for them as it does for a carby
and when they use carbies they have no idea how to tune them to the camshaft ( if its not holley cfm they have no idea)
in a stock 1.8 power goes from 89kw to 105kw factory and that is with 32mm chokes
2000 models have 96kw base and with group1 mods and 32mm chokes jetted
are around 115kw and 34mm chokes they say up to 170hp according to factory spec sheets the group A motor used the C cam same lift
and 45mm dcoe carbs and 37mm chokes these are 200hp beasts
So these cams are not crap they just dont like injection
ps top speed on a factory grp1 is over 215kmh for the 1.8
pending gear ratios
I really should add smooth idle at 850rpm

http://www.alfabb.com/bb/forums/attachments/gt-1963-1977/62561d1175658364-colombo-bariani-camshafts-c-b.jpg

this the original italian dyno results with various cams note the set on 1 versus 3

1 is a 12mm cam inlet  and stock aussie exhaust you have to mod the head to a 12mm to work 155hp
2 is 12mm inlet and 11 mm exhaust and a rise in compression 165hp ( see how the exh cam lets it breath from 154.5hp to 165hp) 10 hp extra
3 is the 11mm inlet and 11mm exhaust 170hp , my option although i dont have that compression Im at 9.7 and i dont have trumpets so it should be around 160-2hp
4 is 12 mm  and 11 mm exh  185 hp  trumpets and extractors is worth 20hp with a 0.5;1 increase in compression
5 is 1600cc setup is thaT 177hp WOW that is for GTA 45mm webers
as you will come to appreciate the 11mm exhaust seems to most important but trumpets might worth a go
I wonder what a euro inlet and the 11mm exh would do
and a 12mm exh is noticeably absent

[bonno]

Hi Carlo
Sounds that you have given the old girl a new lease of life with this mod. The combination of carby and cam versus fuel injection and cam, as you described is so true. Back in the mid 70’s I ran a daily driver Fiat 124 AC that had twin 45 webbers, combined with 30/70 cams, extractors and port and polished head, that use to run like a scalded cat. The carbies were jetted and chocked accordingly for crisp and responsive acceleration, combined with high end revs and power. Back then the use of technology was not applicable/available and relied on the individuals skill for high performance tuning, which has been lost to some extent now days.

[carlo rossi]

I dont know anyone in NEWY that does carbs anymore
they look at you as if you just walked out of then cave...Uuuggh
I think I have worked out why these "bigger" cams are so smooth at idle
When timed right as in not the C &B spec but the group1 spec
the timing almost  matches that off the 10548 cams
except having almost 1mm more lift and slightly more duration due to lift
you get alittle valve tap but it mostly goes away when hot

[carlo rossi]

update on these cams
Alfa 7 in the US suggested setting these cams at 104 deg on inlet 102 deg on exhaust
and not the 110 deg suggested by c and b
and what a huge difference this makes its gives it a much better street range and useable power
max HP at 6200rpm not 7000 where you shouldnt go unless you have done alot of work to the bottom end
and a big hint you have to upgrade your carb jettings and no you dont 45mm webers
40mm dellortos work great primarily because 40mm dellortos have a higher cfm to 40mm webers
40mm dellorto or  solex  same cfm as 42mm webers

[ALF750]

Interesting to hear.   i've just re-assembled a 2Ltr that blew a head gasket.   I'd shaved the head and ported etc, and fitted one of Vince's unlet cams - can't remember the spec but it read very close to a CB47.   Using a 10548 on the exhaust.    Set to the timing marks on the valve caps I measured both LCA's to be 106-107.     I was thinking of spreading them out to 108, but from what you say maybe closing them up/more overlap is a better option? mmmm

[carlo rossi]

the exhaust is too mild get hold of a C and b cam 10.9 mm street for the exhaust
what pistons are you using if they are 10.4 borgo you might have to stay at 106
remember the racing alfas used 99,5  dont spread it it takes it up too high for usable
also now redress the carbs to my spec if you use the 10.9 exhaust
34mm chokes 160 main .8 emulsion 210 air and 58 idle