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I finally smoothed out the 2000 rpm flat spot in my 2L Alfa Ricambi engine. After stepping through the AROO SPICA tuing guide, playing with the timing and changing out the fuel filters, I decided it was time to see what this high rpm engine has for cams.

I bought my current GTV in January of this year and its engine was built a while back by Alfa Ricambi. It has been through a couple of other owners since then, so the details of what parts went into it are now mostly hearsay. The pump was built by Wes to the specs of the engine, but all his records say is 155hp. Looking down the spark plug holes reveals big valves, but I have not had either manifold off, and there are no headers, so I don't know if there was much porting done. Now that I got a look at the cams, I know that they have enough lift to just barely clear the tappet cylinders without having to shave them down. The intake cam is stamped AR109.252 S and the exhaust is AR109.262 S Does anyone know the lift, duration and origin of these cams?

I advanced the intake cam by one adjustment hole (both cams were previousely set exactly on the marks) and the annoying stumble that had been preventing me from driving smoothly and gently in the neighborhoods smoothed out perfectly. I can still make it buck barely, but only if I really try. It is very gratifying when an adjustment pays off so well, especially after having tried all the more obvious fixes first (injection and ignition).

I chose to try this adjustment after reading about intake flow reversion as described in Jim Kartamalakis' book entitled "How to power tune Alfa Romeo twin-cam engines for road and track". This is a fantastic book that should be in everyone's library.
 

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Well that is most interesting ... better get that book.

As for working out what the cam specs are I suggest measuring them, i.e. with a degree wheel and a dial gauge you would be able to work the specs out.

Why do I suggest this?

Well I found it extremely difficult to get this sort of information out of Alfa Romeo for Sud cams, maybe they are better for the Nord engines ... but I doubt it.

Thus I grind my cams to a Cosworth grind and thus I know what it is ... :)

Pete
 

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Discussion Starter #3
Cam Codes demystified

Regarding the numbers stamped into my cams:

A quick call to Ryan at Alfa Ricambi confirmed that the above cams are from Colombo Boriani (no time to look up the spelling). The 109 refers to 10.9 mm of lift and the 252 and 262 refer to degrees of duration.

This seems to confirm the logic that the intake ports were experiencing reversion turmoil at low rpm. I am still a little baffled at how well it idled, even before I advanced the intake cam.

I am very happy with the performance and drivability of this setup. Now I need headers.
 

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I'd buy a cam degree wheel and set them correctly to the specs now that you have them. You might make the engine even happier :)

Once you play with performance cams the marks on the cams are never accurate ... must be dialed.

Pete
 

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Oops I have just realised that you still do not know when they are supposed to open and close, etc. Surely where you got the other specs from has this information too??

This is the main reason why modified engines never work ... all the special components have not been dialed and configured 100% ... this is also why a race engine builder costs so much as these things take a lot longer than just setting to the marks :)

Good luck
Pete
 
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