Cam lobe design/selection/ordering
]Richard, thanks for your reply to my inquiry regrding cams, original post was noisy valves. I suspect the problem is due to them being old Shankle 7Ls set a bit loose. I have been studying your web site and what you have to say about torque, and you've got me convinced. Am I to understand that your reccomendation for a 2 litre street motor would be your 136-785 combo? Can I bolt these up, degree them in, set the valves and go, or will these require notching the tops of the tappet bores to clear the lobes, and a tear down to check piston clearance? To buy a set one simply contacts Webcam directly? Thanks, Steve
The grinds you ask about 136/785, are fairly agressive HP cams and unless most of desired performance is on the track, less might be better.
Since there is nothing but speculation (the Alfa BB`s favorite activity!) on what cams you have I would suggest that you measure (base circle ,(side to side) & lobe (top to bottom) this generally works on street cams) & determine what lift you have as a start, and deciding on desired performance change as a result. None of the aftermarket "pointy lobe" cams in the 10.4 to 10.9 have duration of more than 236-240 at lift at .050. I would suspect these are reground cams with the bodies ground down as well. (will appear to be billet cams) Typically cams with smaller, underground base circles will be much more noisy than the same lobe in a stock (.1080) base circle.
While on the subject of base circles... The typical stock 4 cyl Alfa head will allow fitment of stock base circle cams of no more than 10.5 to 10.9mm lift, without interference with the sides of the cam follower bores. Depends on the year made. By reducing the base circle 1mm you can increase the lift by 1mm. This reduction will require shim thickness increase of .5mm (.0200) more or less. ( Standard C&B base circles seem to be -1.5mm(1.020))
If I was to pick a grind that I would reccommend as a great all around cam for 1750/2liter it would be the RJR 590 grind. It can be used with RJR776 as exhaust( both covered on website) & be very effective for performance yet remain very drivable. Above 11+- lift you enter the world of valve spring bind/piston clearance/valve seal interference etc. 12mm lifts are really only justified on modified heads & racing applications, You get parasitic drag with higher lifts, that are pretty significant. On a street/track day car it really isn`t necessary. But for a track & street oriented 2 liter I would suggest the RJR221/776 (not just for VVT, but modified VVTs are a good idea in a Street/Track application).
Then the next step would be the RJR136/785.
To exceed lifts above 10.5 on 1300/1600 cc motors and 11mm on 1750s is a waste of effort. (I guess I should put IMHO just so I don`t have to listen to other`s who have a different oppinion... I say that as, with available room for valve seat & valve size increases, porting & bowl shaping, more than those lifts won`t allow anymore flow than those lifts will accomodate. More important is the lobe shape above .100 lift and below .040. But what do I know.
There is a possibility that cams with "dumb" lobe design or some of the higher lift stock cams to be reshaped (10548-01 & 51) to reduce overlap & improve lobe design. This is generally less cost, but they must know what lobe design can be ground on the lobe to get the shape needed, as the machine must contact the lobe continuously (removing more material from various areas than others). For this to be done the profile must be known, and what is fitable must be known.
Additionally in the case of 6 cyl cams, you will need how much (in degrees on the camshaft that you want the lobes moved both advanced / retarded, (the new lobe separation/ lobe center) wanted. This is critical not only to performance, but for clearing the pistons, and correct overlap for the design. Any change in Duration & lift will require lobe center changes for both lobes (in different direction and degrees) to perform correctly.
You can order cams to be built direct from Webcam, 951-369-5144, ask for Debbie (AKA "Fluffer"), (there is also a link to them on my Website) but you have to have all the necessary info and specs for what you want or you will likely be sent away for guidance. For 4 cyl. Alfa cams they will want the Grind number for intake & exhaust, and base circle wanted, You must provide cam cores for them to work with. They do not use billets for these, or keep in stock Alfa cams. FYI billets, even hardened are about 30% less durable than their hardweld process
