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1963 2600 Sprint, 1974 Montreal
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Discussion Starter #1
Hello,

I own a 2600 sprint for more than 10 years now. When I bought the car, the engine was far to be strong and we saw that the camshaft was quite worn.
As I didn't find old stock, I purchase finally performance camshafts in Paris at the Garage Espace Century, a specialist Alfa and especially 2600.
Those camshaft never worked fine and the car stayed there for years.

Finally decided to restart the project and upgrade to Weber with a modified weber intake manifold. Even if it's working better and I have power in hi-revs, the car lack power and torque below 3500 rev.

My first problem is to understand the origin of those camshaft. Here is the paper I got at that moment. Does someone recognize something ?
On the cams themself, it's written 154A MR

Thanks

Thierry



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Richard Jemison
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7,381 Posts
The cams are typical old designed cams with lots of early duration (slow ramp rates) that cause lots of overlap that kills low end torque. Basically they are a race cam. I`m afraid if you set the cams to a more appropriate Lobe Centers, the overlap might cause more issues.
I`ve built several sets of cams for the 2600 engines, and you can likely get some of these people to describe their higher Tq/HP and low RPM drivibility. These are a specific intake cam lobe design and a specific exh lobe design with lifts of 11.3MM

Send me an email and I can send you the PDF file of cam designs.
Rj
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If you don't go with Alfar7's suggestion, just get a standard camshaft made. Camshafts are not complicated things to make for a machine shop. Been there and done that ... 25 years ago. Take the old one along so they know where the lobes need to be, tell them the base circle you need and the lift you are after and get them to leave a rectangular blob there. Then send them to a camshaft grinder ... add a hardening process or 2 ... done

BTW: I bought performance camshafts from Italy for my Sud race motor before we made some, and yes we also struggled to get them to work, and binned them. An engine is an engine, we don't need to get this stuff from Italy ... the language and time barrier is too much effort
Pete
 

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Thierry,

Colombo & Bariani used to make 2600 camshafts until the early 1990s --- all of them with racing profiles, called Rif. 02 (292°, 10.9 mm lift), Rif. 11 (300°, 11.22 mm lift) and Rif. 43 (304°, 11.28 mm lift), all with 0.5 mm clearance -- so, the cams you have are probably not C&B, but something similar.

While I generally agree with RJ's opinion (I heard good things about hos cam profiles but have not yet driven a car with his cams -- I certainly will consider them for my car when that time comes), you seem to have good new and usable cams. So, what you seem to need is somebody who can give you tuning assistance (and/or teach you how to fiddle with the cams yourself). Once the clearances are set correctly, its a matter of finding out whether or not the cam timing needs to be adjusted in a way that deviates from standard settings -- all of this happens in context of overlap (intake and exhaust valves being open at the same time), and what effect that has for scavenging effects (gases escaping in the exhaust pipe creating a vacuum that sucks in new mixture) and/or back-pressure (exhaust gases pushing new mixture back into intake runner) at what RPM (or for the desired RPM range). I would guess that 300° cams probably are optimized for around 5-6000 RPM -- really the top end of the RPM range. The prize you pay for that is sluggish behavior below 3000 RPM. But cam timing also affects the Weber settings -- meaning it's an iterative approach of changing one thing and then the other (and then do refinements), but I would only change one setting at a time. Other factors that play a role in what the best settings are gas quality and weather (temperature and humidity) -- whatever the "best" settings are you arrive may be, they'r optimal only for that day and that tank of gas on that day (next day will be different as gas components evaporate).

BTW, in my opinion Webers are over-hyped and 45s are overdimensioned for 2600 cars. That Webers come alive above 3500 RPM is common knowledge -- great for sporty and spirited driving for a an hour, but not for day-long car tours (e.g for going to events), where torque and elasticity matter more for cruising. However, having race cams with a Solex setup doesn't make much sense to me (and Solexes are harder to keep in shape than Webers).

As you are looking ito changes, you may want to look at the exhaust system as well: The factory setup was probably too restrictive with the mufflers, and had a sharp 92° bend after the 2nd muffler that had to create back pressure. I've seen write-ups from the '80s where owners suggested (and others confirmed) that the factory mufflers also clog fairly quickly (owners reported better gas mileage of 10-15% after replacing the mufflers). So small changes to the exhaust may make you engine happier as it is.
 
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