ET: Engine (Twin) Cam Identification

[LoneStar]

Hello all,

A while back I acquired a set of cams for my Rapide project, in about new condition. Based on the 'X1' stamping, I thought they were the Andrews / Megacycle X1 grind, with lift .330 and duration 254 degrees, measured at .050". These are described as "Improved version of Mark I profile. Touring profile" - just what's wanted.

Alas, my cams are not these. Examination shows they're pretty much a race cam: lift is a whopping .470", duration 280 degrees measured at .050". In addition to 'X1', they're stamped '90'.

Does anyone know their origin?

Thanks,

 

[Whiteshadow15]

Sounds like what was in our collection. All of the cams were made through Andrew’s. If I recall we had x1 and x2 cams and some were marked 90 and others 112.

 

[LoneStar]

Dan,

That makes sense; I think I bought them from you. But Andrews originated the X1 grind and then passed it along to Megacycle, with the Mark 1 touring specification mentioned. The Mark 2 style was / is labeled 'X2". Apparently Andrews also used the 'X1' designation for these much different grinds, maximizing confusion.

Any information on their intended use, or what the '90' and '112' signifies? I'd guess them to be a race grind.

 

[Whiteshadow15]

There was never any information on the specifics of the cams. There was a bunch of correspondence between Andrew’s regarding orders was all. That’s odd that they would use the same designation for different products.

 

[bmetcalf]

My ~1982 vintage Andrews MK1-style cams are stamped X1, but no other numbers.

 

[davidd]

I have seen X1 90, 108, and 112. I do not know what the numbers mean. It would be easy to say it is the LSA, but 90 is very tight as the MK2 is generally around 97 at 0.050" lift. I have degreed a pair of Andrews cams that had a 0.470 lift on the Ex valve and, oddly, 0.459" lift on the intake.

To get this lift on an Andrews cam you have to grind the base circle. I don't know if it was Andrews that ground the base circle, but it looked like a nice job. It was not perfect, but I suspect it is difficult to make two cams match exactly when grinding the base circle to make more lift. The LSA on these ground cams was 118.75. The exhaust duration was 0,275". I have been referring to the long cam for these figures as they were at hand. I have been using 0.50" to measure.

I would have thought that when Megacycle purchased Andrews cams that they abandoned Andrews' numbering system, but I have never discussed it with them.

David

 

[oexing]

Thumbs up for your Andrews cams, I think they made the best anywhere available. Stop all that guesswork and check the equal lift at overlap: The Andrews Mk2 , marked as MX2 , got 4.37 mm at overlap according to my Sony encoders. This is typical for very sporty cams, near race types. For common road use you´d see 1-2 mm at overlap. I am not sure about total lift , think around 9.5 mm . So this is a good way to know what you got. Marks on pushrods with felt pen should do for checking overlap lift, no need for the numbers lottery from handbooks.

Vic

 

[davidd]

On the Andrews cams I measured, equal lift was at 0.1385" or 3.51 mm.

David

 

[oexing]

Hmm, 3.51 mm does not look very radical. What was the Andrews numbering on this cam ? Or what was total lift with this type ? I´d think overlap lifts were very critical for behaviours of engines in allround conditions from idle to road speeds, so when seeing numbers above 4 - 5 mm I´d be sceptical about road use .

Vic

 

[davidd]

Vic,

I checked the Andrews cam for someone else, so it is gone now. I have a set of stock Andrews cams, but I have been using another cam for racing. That cam has an equal lift at 0.229" or 5.81 mm, so I was thinking along the same lines that you are. The 3.51 would not be very hot even though the lift was high. It was destined for racing use.

David