variable cam timing old school

[Lynn]

In today's electronically controlled engines, variable cam timing is common.

I remember seeing an "Honest Charley" ad late 60's or early 70's for a lower timing sprocket for SBC engines that retarded the cam timing with rpm. I have never seen one, but my understanding was that it worked by centrifical force pushing spring loaded weights out farther and farther with speed. It wasn't just multiple fixed keyways. Don't know if it fit under the stock timing cover.

Anyone ever see one? Are they still around? Down side?

Seems like a good idea.

[John Brown]

I've seen that type of deal for the upper sprocket. It was called Varicam I believe.

[PxTx]

I'll look for a pic, but I thought those were influenced by oil pressure more than centrifugal movement. Still done the same way on modern engines, but they have solenoids to help control the oil flow.

Well, I looked it up quickly and found this thread:

http://www.jalopyjournal.com/forum/showthread.php?t=629885

Clearly, I was wrong. I'm pretty sure I've seen someone with an old oil pressure variable cam.

[Lynn]

Yes, it was the upper.

And yes, I think the varicam is the one I was thinking of. Seems like the purchase price at the time was $38, or something just under $40.

[PeteLeathersac]

I remember upper gears w/ I think a sliding adjustment fixed w/ bolt(s) & no need to remove/adjust by spline/keyway.
Can't recall ever seeing any w/ the centrifical style but it sounds cool!

<<GRAEMLIN_URL>>/beers.gif
~ Pete

[Lynn]

Not sure I see any centrifical parts on that.

My curiosity is piqued, so I bought the Nov 67 issue of PHR which has an article on it.

Besides, should have some other cool stuff in that mag.

[Lynn]

According to one guy here, they tended to self destruct.

http://www.chevytalk.org/fusionbb/showtopic.php?tid/256206/

[RichSchmidt]

O.K. I will chime in. I always noticed that my old junkyard engines always ran their best right before the stock nylon gear set self destructed. From personal experience,I could guesstimate that the barely intact ones that I swapped out before they failed had a hefty 20 degrees or so of slack in them. Even a conservative 50/50 split puts that at the cam running 10 degrees back during acceleration which is like adding 20 degres of lobe duration without the side effect of additional overlap. It was like a free cam swap. I have pulled out sets that had fewer teeth then a back alley crackho!! <<GRAEMLIN_URL>>/smile.gif