Cam advanced too far?

[mag2555]

I have a question for folks here who grind Cams in regards to what Bill just posted about a Cam being off 17 degree's, which sounds like a bunch to me, not that I am not believing Bills findings, but at what point would you have to say that the Cam was ground on the wrong core or something?

[gottago]

I thought there was something more being said here than there was apparently..The terminology "equal lift points " confused.. I take it he meant equal valve opening points? Not equal amount of lift.. or am I missing something?

Use two dial indicators, one on each lobe I and E, and see where the equal lift point is. If it is more than 4* BTDC you should fix it

What happens with early or late I/o or ex/o ? In general how many cams both intake and exhaust side fit the 4 degree criteria and if not, are they "needing to be fixed"?

Re the cam manufacturing, I've seen one off by 6 degrees, that's about it.. I thought I had one off by way more but it ended up being an older grind cam with a newer timing gear issue. bbf .. Hard to believe the 17 degrees was due to cam alone..

[Ed Wright]

re-

You owe it to yourself to check. It's a lot easier to fix it now than after it's installed in a vehicle. Use two dial indicators, one on each lobe I and E, and see where the equal lift point is. If it is more than 4* BTDC you should fix it. Usually best equal lift point for SBC is 2* BTDC.

Is that 2* applicable to all sbc "no matter which cam"..

Been doing this a long time, and have not found that accurate at all. Nor that checking method.

[gottago]

Lots of people read here and take some of these comments as gospel .. thanks for the double check.. ..

[MadBill]

It would be better than nothing (i.e. it would have raised a flag with that loony Lunati), but there are too many variables for it to be relied on completely, e.g. duration split, asymmetrical lobes...

[CharlieB53]

.. Hard to believe the 17 degrees was due to cam alone..

Using lower quality/older unknown parts I can easily understand tolerances stacking up. 4 degrees each in the crank keyway, crank gear keyway, cam gear, and the cam itself can easily add up to 16 degrees by simply lining up dot to dot.

Small wonder so many engines manage to run acceptably well.

[MadBill]

Checked out a friend of a friend's SBC just-built hot rod that was reported to be pretty lame power-wise. Found and corrected the one-tooth-out cam timing. Third hand report back was "It doesn't run much different."

[engineguyBill]

Most cams are ground slightly advanced, but the 5 degrees that Crane quoted you seems excessive to me. Harvey Crane did own at least a couple of the OE camshaft grinding factories which were/are located in Western Michigan (Spring Lake area), which grind cams on a high volume basis for OEM and crate engine applications. Personally, I only install cams with 2 degrees advance - if necessary - anything else is a band-aid fix. If the cam needs to be advanced or retarded excessively, then it is the wrong cam for the application.

[Geoff2]

Most Crane 'shelf' grinds had 5* of adv ground in. Comp uses 4*.

[Geoff2]

Then there are the 'rule breakers' that win. They don't use the generic 106-112 LSA, or the 'normal' 4* of adv....or extra exh duration....or long rods.

Jon Kaase won the 2008 EMC with all the above attributes. A cam with less exh duration than the int, on a 98 LSA, 92 ICL. 5.965 rod with a 4.00 stroke...

[Ed Wright]

Then there are the 'rule breakers' that win. They don't use the generic 106-112 LSA, or the 'normal' 4* of adv....or extra exh duration....or long rods.

Jon Kaase won the 2008 EMC with all the above attributes. A cam with less exh duration than the int, on a 98 LSA, 92 ICL. 5.965 rod with a 4.00 stroke...

Depends a lot on the heads, and needed torque curve.