For those interested we put together a list of advertised Milwaukee-8 cam specs for assorted manufacturers. We will continue to add to this list as new cams are released. This list can also be found on the FM University site > https://university.fuelmotousa.com/article/cam-specs/

 

Thank you for posting this information.

 

Sticky!!

 

I suddenly have cam envy again, Jamie. We talked about this, damn it.

 

Thanks Jaime, but maybe the Feuling 508 should be Hi Lift

 

We've updated the listing and have added specs for the stock 107/114 and 117 CVO cams > https://university.fuelmotousa.com/article/cam-specs/

 

FM, thanks for spreadsheeting M8 cam specs.

In all due respect, the “open” and “close” cam timing specs are taken at .050” lift and not .053” lift by all of the M8 cam manufacturers listed in posts #1 and #6.

Harley and most, if not all, of the Harley aftermarket cam grinders have been using Tom Sifton’s de facto .053” checking point going back to the 1950s, and even earlier. Sifton’s objective for using .053” instead of lower lifts, such as .006” was to move the checking point off of the cam’s ramp for greater accuracy. Some manufacturers have also used .020” lift points for specs, but it’s not applicable to this discussion.

With the introduction of the M8, Harley “subtly” changed to the de facto "automotive" .050” lift checking point, which has resulted in some inaccurate technical documentation being published and confusion.

The difference in duration between .053” and .050” lift is small, but it is there. Readings taken at "less than" .053” lift result in a greater amount of duration along with an earlier valve opening and later closing. And the difference increases the greater the checking point deviates below .053”.

Harley SE, Andrews Products, Comp Cams, Cycle Rama, Feuling, Max-Cell, S&S, T-Man, Wood and Zipper’s Red Shift all specify M8 cam timing at .050” lift, although it may not be clearly stated.

The only exception that I know of is Chris Rivas, who uses Tom Sifton’s .053” lift for M8 cam specs.

S&S uses .053” lift checking from the Ironhead Sporty, Shovelhead and through the Evo Big Twin and Evo Sporty motors, and even for the X-Wedge motor.

Then starting with the Twin Cam and continuing with the M8, S&S stopped publishing (not sure why) cam checking lift specs. But S&S is now using .050” for the M8 cam specs and “supposedly” the same value for the Twin Cam”.

 

What could the motivation be for changing the checking height of a cam? Is this some minor way of increasing duration without alerting EPA when HD submits their cam specification updates?

 

Checking a cam’s specs at different lifts changes nothing about how the cam is ground. The engine sees the same amount of valve duration regardless of where cam timing is checked: .006”, .020”, .050”, .053”, or any other lift.

Most aftermarket performance cam grinders went to checking their M8 cams at .050” to stay in lockstep with the MoCo. However, I can only speculate about why the MoCo moved from .053” to .050”, but I doubt it has anything to do with EPA regulations.

As I previously mentioned, Sifton moved from .006” or .020” to .053” because cam movement (AKA lifter movement) at .006” or .020” is slow, difficult to detect, because the lifter is on the cam’s ramp. In this case, you can check cam timing 10 different times and get nearly 10 different readings. In other words, you are unsure about what is the correct reading and are chasing your tail.

Regarding the MoCo, they do strange things at times that makes little sense to anyone else. But always remember, the MoCo is more of a marketing company than an engineering company. Indian flat trackers are currently proving that point.

However, I suspect the MoCo changed from .053” to .050” lift to be consistent with the automotive and import motorcycle industries. Most if not all of the import bikes check cam timing at .050” lift, and so do their aftermarket performance cam manufacturers (e.g., Web Cams).

Automotive performance cam manufacturers always used big numbers to help sell cams, such as big high-lift numbers and big-duration numbers. .500” lift cams looked wimpy compared to .550” lift cams, so many car racers bought .550” lift cams. That’s probably less so today than yesterday.

Many auto cam grinders list cam specs at .050”, .020” and .006” lift. The duration measured at .006” lift is larger than when measured at .050” lift. So some cam grinders would display cam specs at the .006” or .020” lift values instead of the smaller .050” numbers. Uninformed racers would tend to buy the biggest cam. After all, if a little is good, more must be better. This example is about the same cam with the same lobe shape and specs, but the specs were just measured at different points, some of which measured larger, but it is the same cam. Bingo, maybe that’s a sale, who knows.

However, comparing the difference in duration between .020” lift and .050” can give a “general indication” of how fast a cam lifts. In general, the greater the duration differential, the faster the lift rate will be.

There is something call “cheater” cams used in racing where the duration and specs of a cam are regulated, so every racer has the same amount of valve duration and O/C valve timing. However, a cam opening at the same point of another cam but with a faster lift rate puts more “area under the curve,” thus theoretically more cylinder filling. Since cheater cams lift faster and jerk rates are harder, they potentially produce more valvetrain wear and noise.

Since 1971, Andrews Performance catalogs have always listed cam specs at.020” and either .050” or .053”. Checkout out their catalog and factor in what I just described when reviewing a cam’s specs.

Some on this site poo poo cam specs and want to keep the rider dumb down, in the dark and subservient. However, knowing cam specs (and other engine specs) can offer lots of useful information if you know how to interpret the data. If you know how to interpret specs, you can turn “plain data” into “useful information.”

When building an engine, if you don’t know where you are, you can’t know which direction to go: more or less duration, more or less lift, more or less overlap, different lobe center lines or lobe separation angle, faster or slower opening/closing ramps, etc.

In the land of the blind, the one-eyed man is king!

 

Possible typo; HD shows the Stage 2 447 cam intake closes at 17 ABDC, but you are showing 7?