Alfa Romeo Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
I just bought a set of performance cams from a 2.5 12v Busso engine to use in my 3.0. However I would be interested in who the source for the cams were.

The seller stated he had seen no marks (going to look myself to) and that he believed that they made maybe 20hp on his 2.5 otherwise stock engine. They are ~15+ years old but not used much, originally installed by Italauto in germany.

I have measured the intake lift to 11.2mm and exhaust to 6.3mm. Base circle is 27.3mm.

Are there any other measurements that could help identify the source?

Also, should I swap the valve tappets for new ones while I re-shim the valve clearance?
 

·
Registered
Joined
·
4,662 Posts
11.2/6.3?

They look somewhere between C.B. Race Medium and Road Max.

The differences could well be down to Colombo Bariani, slightly modifying the profile for a customers requirements, which is the beauty of their camshafts and the support C.B. give to their "Clients".

Either way, It doesn't sound like yours are Granny's Cams! Plus C.B. do not identify their cams, beyond the original packing boxes. They do not give anything away free.

You pay a lot for them, but you get a lot from them. However, if you post a picture of them, there are a few clues to the trained eye!

20 bhp on a stock engine is not unrealistic. 12.5% on a standard 2.5 @ 160 bhp is actually quite conservative for C.B., if they are edging towards race medium.

Alfa Romeo
Alfa Romeo - V6 2500-3000 12V
[AR6.CM1]Race medium11.48300° / 304°
[AR6.SM1]Road medium10.46.4294° / 264°
[AR6.ST1]Road max10.76.5290° / 268°
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
Some pictures. Haven't unpacked the other one yet, from what my unexperienced eyes can tell there's a black coating on the nock's that has been partially worn off. Especially at the top of the nocks where the surface is blank. Most area of the nocks have slight groves that look like they are from the production, this is what I interpet as that the cam's don't have that many miles on them. There are also two notches at each side of the middle bearing.

I have only measured one nock of each yet, and looking at C&B's profiles it could be possible that the intake has the Race medium profile and the exhaust the Road medium or even road max profile. According to the previous owner the car these were in felt "normal" up to about 3000rpm then pulled freely up to about 7000 rpm. That do suggest quite a bit of duration atleast.


Tool Automotive tire Auto part Cylinder Bumper
Tool Household hardware Nickel Gas Auto part
Tool Composite material Auto part Fashion accessory Titanium
Nickel Office supplies Auto part Blade Metal
Automotive tire Tool Coil spring Auto part Automotive wheel system
 

·
Registered
Joined
·
4,662 Posts
I believe they are Colombo Bariani.

The original 2.5 V6 was fitted with six carbs - Dellorto's were fitted to early versions in the Ala Six.

The Bosch Fuel injection was not around at the time and it is said Giuseppe Busso was not happy with the throttle response with anything, other than individual Throttle Bodies, a - la twin cams. However, they were pigs to get right. So it may be the "Tame" exhaust profile was intended to make it a bit more stable at tick-over, where the race - medium would result in a very lumpy idle, unsuitable for road use. Reducing the overlap would help enormously whilst keeping a healthy inlet valve lift.

Inlets being on shims, they could be set up accurately and remain so for a good while.

But, with the exhausts on the horizontal push rods, a certain latitude is given to the way owners set them up. You ain't got much latitude with 304deg. duration, whereas 264/268deg., you do.

Then Bosch came along with their fuel injection system that worked brilliantly. I think it was a watershed moment for Alfa when they fitted that to the engine. It probably did a lot for C.B. too, because camming and engine up until that point was not for the faint hearted. Now, it easy - peasy.

P.s., My 3.2JTS has C.B.'s and they have 11.4mm. lift with 278deg. duration on inlets and exhausts. And it is rock steady at tick-over.

However, characteristic of C.B. they set the engine on fire @~ 3-4000rpm onwards. Very tractable at low revs, but coming on strongly as the gases increase in velocity. I think your cams will take you by surprise - big time!
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #5 ·
Sounds like good news then :) The engine I have is a 3.0 from a 164, I'm also doing some intake modification, most likely it will be custom pipes that taper from 43mm ID to 39mm ID at the head and two 75/GTV manifolds welded together for a plenum (and of course velocity stacks inside the plenum). I'm also going the E85 route with an aftermarket, programable, ECU, new exhaust system and an open air filter. Hoping for 210-215hp atleast which feels very doable with these cams :)

You seem to be expereinced with these engines, should the bucket tappets be changed when I change the cams? Shims I suspect that I should be able to check the clearance on the stock setup and measure the stock base circle, then do some math and that way be able to calculate what schims I will need?
 

·
Registered
Joined
·
4,662 Posts
It really depends on the condition of your buckets. If they show signs of scuffing - change them. But if the engine has been well treated, with regular oil changes, they could be good. But make sure they are pretty clean as you don't want to wear your cam lobes because the buckets have become scuffed. If in doubt - change them.

I found the real problem was on the exhaust valve guides, wearing oval. But it was an early engine and I am informed they resolved that problem.
 
1 - 6 of 6 Posts
Top