[PAUL K]

A lot depends where you purchased the cam from. If it's a custom grind cam manufacturers grind the cam straight up, unless specified at to point of order.

One of the more popular "billet' timing chains is almost always off when installed dot-to-dot.

2 & 4 degree keys are readily available, although they're actually closer to 5 & 8.

Timing chain sets offering three offsets, +4 , straight up, -4 are usually eight degrees each.


Back in the day magazines made a big deal about advancing and retarding camshafts for improved performance. Most of them recommended advancing high performance street camshafts four degrees. They seldom mentioned that almost all aftermarket shelf grinds had four degrees of advance ground into them. They never mentioned the "four degree" slots was actually eight. So the trend was to install the cam that already has four degrees of advance and advance it another eight by using the four degree advance slot and then wonder why the car ran like poop.

The old normal when hardly any custom cams had advance ground into them was to use a 2° offset key to retard the cam and the 4° advance slot on the timing chain, you'd end up with three degrees of advance.

All the above was figured out with a degree wheel.

[Formulajones]

All the years I been doing it, they are never exactly right out of the box.

It's not just the cam, nevermind the cam specs possibly being off, you also degree for other reasons. All the key ways on the crank, on the cam sprocket, on the crank sprocket, on the cam itself all are built with a tolerance that isn't exact and all those tolerances stack up.

All it takes is a keyway to be off a degree here, a degree there, and next thing you know you think you've lined up your dots not knowing the cam is off 2-3 or 5 degrees in one direction or the other.
Will it run ok? Sure. But not optimum.
I've seen them off as much as 6-7 degrees and I remember an engine builder telling me he's seen even more.

So it's always best to check to make sure the basics are set. Then if you want to get fancy and check intake to exhaust lobe relationship on overlap and move things around to really dial things in.

[scott70]

I look at it as peace of mind. I’ve had a few cams that were way off. Had to actually send one back. It might run ok if it’s a few degrees installed one way or the other but I don’t want to leave any power on the table because I didn’t have it checked to make sure the ICL is at 108 like intended. If you got a cam that degrees into spec and you got to have the timing gears dot to dot then you got a good one. .

[mgarblik]

In my engine class we degree 12-16 camshafts a year. I have a data pool of about 30 years worth, all kinds of engines. These are approximate results from all those engines. About 1 out of 10 engines are within 1 degree of perfect. +- 1/2 degree. About 6 out of 10 are within 2 degrees. +-1 degree. about 2 out of 10 are within 4 degrees. +- 2 degrees. About 1 out of 10 is off more than that. The worst Pontiac engine I have degreed was out 14 degrees. It was all in the timing set. This was over 20 years ago and it was a cheap "Wolverine" timing set. No idea if they are still around. I tried it several times and after giving up in frustration, I installed a used timing set I had laying around as a test. It came in within a degree or two. So the keyways in the "Wolverine set" were off by a bunch. That was a real outlier.
As far as effects: In a street Pontiac engine 400-500 HP, I doubt most people would notice a 1 or 2 degree variation in cam timing. Engine may be a little soft at lower RPM's if retarded 2 degrees. People with a well calibrated "butt dyno", would probably feel a slight difference at 4 degrees. So is the process absolutely necessary? Not really.

But it is part of doing a really nice engine assembly. Part of "blueprinting" an engine. As part of the process, most engine builders verify the opening and closing points of the intake and exhaust valves and the lobe lift. Along with setting the intake centerline right where the cam grinder expects it to be. More peace of mind for the best finished product.

[Singleton]

Originally Posted by PAUL K

The old normal when hardly any custom cams had advance ground into them was to use a 2° offset key to retard the cam and the 4° advance slot on the timing chain, you'd end up with three degrees of advance.

That's a great idea, I would have never thought to do that.