Series 1 Cam sprocket (split from another topic)

[myfirstbonnie]

Are we going to work on that cam sprocket too?

(Edit by Admin for the split topic, this is in reference to a tiny problem encountered on the Zilla):

[willwren]

I need to come up with an OEM sprocket first, then send it out to be hardened in the center only. The intercooler itself doesn't add more stress to the valvetrain, so that won't get worse from where I am right now.

[GonneVille]

You know, getting a new sprocket cut from billet probably wouldn't cost that much.

[willwren]

Billet what? What alloy? What hardness?

Billet doesn't mean a whole lot, Brian. It's alot more complicated than that. The teeth of the sprocket can't be too hard, or the teeth will break off, or even worse, wear the chain prematurely. There is no strength in 'billet' anything if the alloy or the hardening processes aren't up to the stresses, loads, and wear the part will be subjected to. Billet mild steel and billet cold rolled steel would have a 50% strength/wear difference without tempering or hardening.

If there was an EASY solution, the Series 1 would have a double-roller timing set like the Series 2, but with no aftermarket, the difficult solution begs to be solved. In my case, I have to start with the highest quality part possible (which I believe to be OEM AC DELCO) and harden ONLY the center portion in a radial fashion. The trick is to not harden (temper) it to the point that it's brittle, or it'll just BREAK instead of wear (the last one lasted brand new for 500 miles).

The biggest problem with the cam sprocket on the Series 1 is that the key doesn't fully extend into the sprocket, and the cam would need to be modified to allow that. But at that point, the cam is shorter than the key, and still doesn't extend more than 2/3 through the sprocket. So a washer would have to be welded to the face of the camshaft, a keyway broached or EDM'd through it, then hardened, then the sprocket........

That's the ideal solution, but I'll take it in smaller steps. I'm not planning to add more load to my valvetrain. I just need to improve what I have, not perfect it.

Wow. You bastard. You took us WAY off topic, Brian.

[TenGHz]

What's a slushbox? Is it like an ice box for an inner cooler?

Excuse my ignorance, it's just that every time I've heard that word used before was by ricers talking about automatic transmissions.

[WhiteArrow3800]

The biggest problem with the cam sprocket on the Series 1 is that the key doesn't fully extend into the sprocket, and the cam would need to be modified to allow that. But at that point, the cam is shorter than the key, and still doesn't extend more than 2/3 through the sprocket. So a washer would have to be welded to the face of the camshaft, a keyway broached or EDM'd through it, then hardened, then the sprocket........

Thats what my dad suggested to do, when I told him about this issue, well your issue, none of us are pushing an S1 like this. Which sparks another idea, the Aussie's play with the S1 don't they? Might they already have a solution?

What do you mean the cam is shorter than the key? Mine is flush with the end/face of the cam.

Sorry if this is too off of the intended subject.

[willwren]

Not too badly off-topic, as the intercooler will prevail over the next couple weeks. Even though the two topics aren't related at all.

The failure of my cam sprocket was directly caused by the increased load on my valvetrain. 1.8 rockers by themselves add more load, but probably not enough to cause this. I beefed up my valvesprings in order to kill some valve float at the top of 2nd gear at the same time (my shift points are higher than most S1 L67's), and made worse by performance lifters with half the preload of OEM.

Solutions:

1. Extend the camshaft which currently only extends 2/3 into the sprocket by welding a hardened washer to the end and turning it back to OEM spec diameter, then have the keyway EDM'd (can't broach a hardened forged camshaft keyway) so the keyway also extends JUST SHORT of the outer face of the sprocket. This adds 33% more load bearing area.

2. Fabricate a custom double-roller setup (not as impossible as it sounds, but a great deal of work). This would still require option #1.

3. Having a good idea what material and hardness the key is, have the CENTER portion of an OEM cam sprocket hardened to withstand the increased load of my valvetrain. It's important NOT to harden the sprocket tooth area, as this will increase the rate of wear on the chain. Sprocket tooth wear is not a concern typically anyway, and you don't want those teeth to be brittle. Harder=more brittle when dealing with steel. The problem with this option is knowing the specific alloy of the OEM sprocket, but that's not as impossible to find as you might think.

For the time being, my supposedly 'better than oem spec' Cloyes timing set failed, and I'm back to my last spare cam sprocket (the other became a WCBF trophy this year). My work for now will be focused on option #3 and a used OEM cam sprocket, and if that fails, I'll go back to option #1 using my spare camshaft and a longer key, while also utilizing option #3.

I no longer have the numbers associated with OEM springs vs. my current springs or 1.6 ratio rockers vs. my current 1.8's, but a few minutes with a load cell at work would determine that again. I can tell you that when the valves are open with the stronger springs and the greater ratio (more compression of each spring), the collective valvetrain load is significantly higher than normal.

I'd be VERY interested (as I was telling Don last night) to know if the Series 2 camshaft extends completely (or more than 2/3 through) the thickness of the cam sprocket or not.

[2000Silverbullet]

I haven't heard of any S2's running 1.9's and heavier springs, like PDad and I, that have broken a cam sprocket....yet.

I remember Rogue showing us his timing chain tensioner that was worn excessively and was blamed on his 1.9's and springs.....that was before his current set up, but he took out his balance shaft and installed a double roller. I think now he has the balance shaft back in and he is running 1.6's with a cam so assume he went back to stock single timing chain.

[willwren]

Paul, your springs and my springs are not even closely related in OEM form or aftermarket. Totally different beasts. My OEM springs are stronger than yours were out of the factory to begin with. Not to mention the actual spring design. Mine are larger in diameter and are cylindrical. Yours are beehive. To take it farther back in history, my springs (OEM) are in fact the EXACT same spring the 85-87 Grand National and GNX have, and the springs I now have (purely coincidentally and discovered after I chose them by John Wikoff and I) are the same springs the GN and GNX use after camming or 'rockering'.

105# is the valve closed value. Spring rate determines (in part, along with rocker ratio) valve open weight. That is the max load (collectively across all 6 springs based on engine rotation) the cam sprocket sees at any given time. With valves closed on OEM springs, there is 10# more load per spring on my engine than on yours.

You can't draw comparisons between Series 2 'known common' configurations and what I have. And that's without comparing cam sprocket design, lenght of the key, cam design, and on and on. These engines really don't have alot in common between the S1 and S2.

[chadow427]

231 CI.

[BillBoost37]

I'd be VERY interested (as I was telling Don last night) to know if the Series 2 camshaft extends completely (or more than 2/3 through) the thickness of the cam sprocket or not.

It does extend to be flush with the cam sprocket face. Only extending 2/3's of the way into the sprocket doesn't seem right. Almost sounds like your key may have been partially nose down in the keyway and prevented the gear from seating fully. This would be tough to see unless the engine was easy to view from all directions. Or possibly under torqued, we understand that this bolt has a serious amount of torque put upon it.

[willwren]

2/3 is normal for the Series 1. My original when it came off was that way. So was this one, and so was my donor motor. Key was flush in the keyway on the cam.

In other words, I have 3 sprockets here, from two engines (and two different camshafts) and all three are the same. And the sprockets are two OEM and one Cloyes. I've covered those bases already.

(probably time to get the IC back on topic, I'll take a stab at splitting this later today when I'm awake).

[willwren]

I now have all the alloy and hardening specs for the part. Just the starting point I needed. It's actually a very specific hardening specification. Most of the hardening is related to the teeth, but when I see the print, I'll see if it's specified in the center for the cam/key.

One more nail in the coffin.

[myfirstbonnie]

The intercooler itself doesn't add more stress to the valvetrain, so that won't get worse from where I am right now.

I understand this, but one question. Won't it see an initial slam as the hammer is dropped and the crank rips on the chain to turn the cam? I understand that once the motor is revving that the only resistance is the valve train, but i am wondering about the initial surge it sees.

[willwren]

Power is applied to the crank, where it overcomes resistance (drivetrain loss and moving a mass). The cam sprocket's load is directly related to the load of the valvetrain (combined spring load) and rate of accelleration (rpm's) not actual horsepower or torque values.

I have the actual GM production prints now. For both the Series 1 and the Series 2/3. They're quite large, so I'll print them tomorrow at work for a side by side comparison, and use that information to help make my decision on the path forward.