Comp cams measurements & discussion

[trinity_gt]

I've got a set of XE262AH cams:

P/N: 102-502-9R and 102-502-9L
Grind: XE262AH-13
Date: (right) 01/17/06 (left) 01/19/06

for my 02 GT and am calling around making queries about the install. Since I fret like crazy over what I consider major surgery like this involving tight tolerances and the like, and since I keep reading alarming threads about issues with CC camshafts, I thought I'd do a few measurements -- what I'm able to measure that is -- of the journals and lobes of my cams, partly to compare to the shop manual specs for the car and partly to see if anyone else can measure theirs to see what they get.

I measured the journals and got the following readings:

(all measurements starting at sprocket end)

Right:
1.0610
1.0610
1.0610
1.0605
1.0610
1.0605

Left:
1.0615
1.0610
1.0600
1.0600
1.0600
1.0600

My FMC shop manual calls for a journal diameter of 1.0615 to 1.0605. Now, since my vernier is not currently calibrated, I'm going to say that being five-ten-thousandths out is as good as a pass.

The base circles measured as follows:

Right:
1.8935 E
1.8955 I
1.8850 E
1.8925 I
1.8930 E
1.8925 I
1.8925 E
1.8925 I

Left:
1.8945 I
1.8945 E
1.8955 I
1.8945 E
1.8965 I
1.8955 E
1.8955 I
1.8945 E

Notice that the base circle of cylinder 2 (right cam) exhaust lobe is 1.8850 which is about 0.010" less than the others...reason for concern? How much "slack" does the lifter preload have for these kinds of variances? Do these absolute values look about right (what's the stock cam?)

The lobe "lift" - base circle to tip of lobe at highest point, are as follows:

Right:
2.1925 E
2.1920 I
2.1835 E
2.1915 I
2.1920 E
2.1915 I
2.1915 E
2.1915 I

Left:
2.1935 I
2.1935 E
2.1945 I
2.1945 E
2.1945 I
2.1940 E
2.1945 I
2.1935 E

Note again how the exhaust lobe for cylinder 2 is showing a decreased lift: roughly 0.010" less than the average... Reason for concern at all?

If I calculate the lobe lift itself by subtracting the base circle diameter from the last measurement there, I get:

Right:
0.299 E
0.2965 I
0.2985 E
0.299 I
0.299 E
0.299 I
0.299 E
0.299 I

Left:
0.299 I
0.299 E
0.300 I
0.300 E
0.298 I
0.2985 E
0.299 I
0.299 E

Interestingly, the FMC shop manual says the roller follower ratio differs for intake and exhaust followers. The intake, they say, is 2.02:1 while the exhaust is 2.03:1. Using the above lobe lifts (of, say, 0.300"), the intake valve lift should be 0.606" and the exhaust 0.609". This ain't right. Hyland's book says 1.79:1. Using that ratio, I get a valve lift of 0.537". This site:

http://www.musclemustangfastfords.com/tech/0302MMFF_MixMatch/

leads me to think my 2002 would have a 1.81:1 ratio. That gives 0.543" which essentially matches the cam card (which says a gross valve lift of 0.545" and a lobe lift of 0.3000"

So what's the right ratio for the followers?

I'd be curious to know if anyone has PI cams lying around what sort of base circle they measure and what their lobe lift is. (The FMC manual says 0.28" intake, 0.30" exhaust which I also think is wrong...).

Thoughts? Any more data?

 

[TGJ]

Hyland's book is trash and the rocker value listed is just one of the many errors in the book. The correct ratio on the followers is 1.81:1.

 

[Red2000GT]

I don't remember the exacvt numbers but I know my Comp's were right around the same specs for base circle. 10 thou difference is a little sloppy but not unusual for production cams that aren't $1000.
I still have my PI's around but it'll be a few days till I can measure them. I honestly wouldn't worry at all. The main issues people have had has been with the XE270's(just like i did),mainly with aftermarket pistons(like i have).

 

[heyzuess]

The main issues people have had has been with the XE270's(just like i did),mainly with aftermarket pistons(like i have).

I didn't know that until AFTER I bought a set of the XE270's, but luckily caught it before the engine was built. The engine builders had to cut reliefs in the pistons to give enough clearance to avoid ptv contact.

I haven't heard of any problems with XE262's...

 

[trinity_gt]

Not really that concerned about PTV with this grind but I've heard/read alot about folks with noisy valvetrains after Comp installs and the thinking was that the base circle diameter on certain datecode(s) of certain grinds was too small, resulting in insufficient lash adjuster preload. Mine are pretty late (Jan/06) so they may be okay... Just trying to check.