camshaft info background needed

[72 1300]

hey everyone has anyone ever heard of an apic ap4 camshaft 3 bolt one.
cheers luke

[Marc]

Years ago you could get these (and the smaller AP-3 and AP-2), they were ground on a new Resolit Brazilian stock blank. Don't know if there are any still available, but they won't be missed.
Since they started with a stock lobe the only way to get lift was to reduce the base circle, so they didn't have much. The AP-4 was something like .360" lift, with absurd duration...I think I've got one around here somewhere that's been gathering dust for 30+ years, can't imagine an application for it. Too much duration for a mild motor and not enough lift for a serious one, useless for the project you're considering.

[turboblue]

I have an NOS AP2 still in the box.
Made in Brazil and has a BAP/Geon sticker on it.
That's all I got.

[Marc]

The AP-2 grind is less ambitious, compares to an Engle W-100 (.385" lift, mid-270° duration) so it would be an OK choice for a mild street motor. Still has a smaller base circle than stock but not enough so to be a problem with new (not reground) lifters.

[MinamiKotaro]

I had an AP3, can't recall the specs but it had a lot of duration and not much lift. It was a top-end only cam, and the top end wasn't even that great. It was worthless.

[72 1300]

cheers everyone,

[Steve C]

Hi

In case anyone is interested these are the specs for the AP cams.

Steve

[turboblue]

Hi

In case anyone is interested these are the specs for the AP cams.

Steve

Thanks Steve

Big jump in duration from 3 to 4...........
Almost like 1st two are at .050" and the last is at the camshaft.

Lots of lash in those cams too......013 to .015???

[Steve C]

Hi

I have an AP2 in a 1904 with 044 heads dual 40 dels etc, it runs nice, very torquey.

You would need a good stereo or ear muffs to run those clearances.

Steve

[Marc]

...Big jump in duration from 3 to 4...........
Almost like 1st two are at .050" and the last is at the camshaft...

The problem with comparing cam specs comes from what the meaning of "open" is.
Take a look at the AP-2 intake valve numbers. Opens at 14°BTDC, stays open until 46°ABDC...14+180+46=240°.
What's unsaid is, just how far off the seat does the valve need to be before it's considered "open"?
The SAE standard is .006". When checked at the valve, the lash and rocker ratio are factors. Using the .008" specified for the AP-2, and assuming they based the numbers on 1.1:1 rockerarms, that means the duration number would reflect the number of crankshaft degrees for which the cam pushed the lifter out by ~.013" or more. Lots of assumptions already, how do we know if they used the SAE standard, or what lash or rocker ratio was taken into account?
What's more significant than "actual" duration is the effective duration - there's very little flow through the valve until it's opened further, so the number of degrees that it's open past some arbitrary point is more representative than the "actual" number in predicting how a cam will work. Most grinders use .050" these days, but .040" (1mm) and other numbers have been used. The same issues as to checking clearance and rocker ratio apply here, too.
It's folly to predict operational characteristics of cams from different manufacturers based upon their published numbers when you aren't given all of this information, since there are too many variables to take into account.

Although they aren't labelled as such, the numbers given on the AP spec sheet Steve provided appear to be effective duration for the AP-2 and -3 but "advertised" duration for the AP-4. Advertised is usually close to actual, but there's no standards of any kind for determining it - the manufacturer pulls a number out of the air that he hopes will sell cams. The difference between adv & eff duration is influenced by all of the factors cited above as well as the length of the "clearance ramps" on the lobe, but you can usually expect it to be between 30-40°.