Cam shaft core materials

[CamKing]

It was a uniform medium grey everywhere except the lobe and journal surfaces.

That's not an 8620 core.
Sounds like a EPC induction hardened core. They're not the best, but they're the cheapest.
Most SBC cams that break, break between the last 2 journals.

[CamKing]

A little off my original topic, how much material is typically left on the lobes prior to grinding? I'm going to reverse engineer a camshaft I have to produce a few cores.

When we're making cores, and we know the exact lobe shape we're going to finish them to, we machine them .020" a side, oversized.

[CamKing]

Question here for Cam King. Does it hurt to have a larger cam barrel than the base circle as long as proper heat treating has been attained? Other than cosmetics and generous radiuses are employed.

If you grind into the core, you now have sharp edges ground into the core, from the edge of the grinding wheel. I don't know if that's worse than the small barrel, but it can't be much better.

[CamKing]

8620
8660
9310
S7
M3

In 99% of roller applications, 8620 is the best way to go.

what are the pros and cons of these materials in this application

What's the exact application?

[CamKing]

In 30 years of this business I have had about 8 or 10 SBC cams break in front of #8 ex lobe. Mostly small barrel stuff. All but 1 was advertised as having been made of 8620. The other being induction hardened.

Question here for Cam King. Does it hurt to have a larger cam barrel than the base circle as long as proper heat treating has been attained? Other than cosmetics and generous radiuses are employed.

The reason the barrel is cut down smaller than the base circle is to keep the camshaft straight because it distributes the residual stresses evenly.

Actually, all cams bend when you grind them. especially heat treated steel cams. The grinding process seems to act like a stress relief, and they want to go back to where they were before they were straightened. That's why we rough them to .005" over finish size, pul the cam out of the grinder, straighten it, and put it back in and finish grind the final .005".

[CamKing]

In 30 years of this business I have had about 8 or 10 SBC cams break in front of #8 ex lobe. Mostly small barrel stuff. All but 1 was advertised as having been made of 8620. The other being induction hardened.

Question here for Cam King. Does it hurt to have a larger cam barrel than the base circle as long as proper heat treating has been attained? Other than cosmetics and generous radiuses are employed.

The reason the barrel is cut down smaller than the base circle is to keep the camshaft straight because it distributes the residual stresses evenly.

Actually, all cams bend when you grind them. especially heat treated steel cams. The grinding process seems to act like a stress relief, and they want to go back to where they were before they were straightened. That's why we rough them to .005" over finish size, pul the cam out of the grinder, straighten it, and put it back in and finish grind the final .005".
Of course, they don't do that with the mass-produced cams.

[MadBill]

In 30 years of this business I have had about 8 or 10 SBC cams break in front of #8 ex lobe. Mostly small barrel stuff. All but 1 was advertised as having been made of 8620. The other being induction hardened.

Question here for Cam King. Does it hurt to have a larger cam barrel than the base circle as long as proper heat treating has been attained? Other than cosmetics and generous radiuses are employed.

The reason the barrel is cut down smaller than the base circle is to keep the camshaft straight because it distributes the residual stresses evenly.

Actually, all cams bend when you grind them. especially heat treated steel cams. The grinding process seems to act like a stress relief, and they want to go back to where they were before they were straightened. That's why we rough them to .005" over finish size, pul the cam out of the grinder, straighten it, and put it back in and finish grind the final .005".

I wonder if vibratory stress relief would be useful re this? http://www.meta-lax.com/Home/Technology/technology.html
FWIW, my 45 year old aluminum BBC heads were warped ~ 0.008" when I checked them after larger interlocking seats were installed. I had them treated and when I later measured, the warpage was down to 0.002-0.003"...

[la360]

The tool steel cores are induction hardened? Or is the core still left soft?

[CamKing]

The tool steel cores are induction hardened? Or is the core still left soft?

The 9310 cores we make are carborized like the 8620 cores.
Our M3 cores are actually thru-hardened

[englertracing]

8620
8660
9310
S7
M3

In 99% of roller applications, 8620 is the best way to go.

what are the pros and cons of these materials in this application

What's the exact application?

Say in a sbc roller

[BBO Omega]

Mike,
Do you offer the 8620 core with the Cast Dist Gear?

[Rick Finsta]

Last I asked he didn't have any for the Olds. I want one for my turbo project and have been looking around for a Crane core like that for some time. They haven't made them in years.

I will probably end up just using bronze since I'm only driving a cam sensor (external oil pump) but when I was entertaining running a Titan I didn't want to mess with the bronze.

[BBO Omega]

Andy had my HR cam ground on one of those cores by Crane a few years ago. I like not having to worry about the Dist Gear. When I pull the engine this winter to have my Converter restalled, and do a lower end check, I was thinking of going with a little larger cam. I speced my cam with 10.6cr and ended up at 11.59cr due to a misunderstanding between me and my Head guy [I said knock off 10. I meant .010" and he heard 10cc].

[CamKing]

Mike,
Do you offer the 8620 core with the Cast Dist Gear?

Yes

[BBO Omega]

Mike,
Do you offer the 8620 core with the Cast Dist Gear?

Yes

For an Oldsmobile?