Anyone have expiriance with the ancient Vari-cam? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 10-21-2009, 05:07 PM
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Anyone have expiriance with the ancient Vari-cam?

I ran across a magazine from 1965, and in it was an ad for the "Vari-cam". It was a camshaft gear for chevy that advanced and retarded cam timing while the engine was running. has anybody had any experience with this? has anybody ever heard of this? I want one bad, thinking about throwing it on my cammed lt1.

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Old 10-21-2009, 05:14 PM
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My uncle tried one way back then on their Sprint Car DZ 302 engine. Found it to be too erratic and ended up just fixing it solid after degreeing the cam . This was after running it for a month or so trying to make it work. Good idea, poor design, some modern cars are using a computer controlled hydraulic version of this concept right now. The old stuff just didn't work though.
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Old 10-21-2009, 07:25 PM
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Quote:
Originally Posted by cusz28
thinking about throwing it on my cammed lt1.
Believe you'd need an electric wp (if you don't already have one) and possibly clearancing the timing cover.

Quote:
Originally Posted by ericnova72
some modern cars are using a computer controlled hydraulic version of this concept right now.
Very true. Even the lowly 3.5L V6 in the better half's Impala DD has it.
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Old 10-22-2009, 11:56 AM
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i have an electric pump so i can use a true double roller instead of the chinsy single butt-link garbage. the only problem i can see would be the distributor either opti or normal style. it would throw my ign timing off. maybe that was the problem back then. if i went distributor less, that would solve that problem. anyone know where i can get one?
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Old 10-22-2009, 12:38 PM
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Good luck finding a Vari-Cam. I never used one, but there must have been reasons it failed to follow us into subsequent decades following its release, as related by the posts above this one.

There is a way to change lift and duration as the motor is running, cheaply and easily. I've used them in a BBC that I knew was over-cammed and they worked like a charm. They're Rhoads Lifters. They make several different styles for different motors. Here are links to the original OE roller lifters and the V-Max roller lifters for roller motors....
http://www.rhoadslifters.com/Pages/O...lOERoller.html
http://www.rhoadslifters.com/Pages/VOERoller.html
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Old 01-19-2012, 10:11 AM
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Vari-Cam & Rhoades a NO-NO!

WE were running in the "STOCK" class with a "Stock" off the shelf GM cam [what a pig]. I went down that road trying to move the cam ahead when we came out of the corner.
Bill Coleman [ who has built more engines than U & I have ever seen], and Billy Gwynn {rip}[Nascar Nationwide engine builder] were experienced with the products. Bill said he had never seen a vari-cam that didn't end up with the mechanism in the oil pan, and a bunch of bent valves [or the engine blown altogether]. Billy said, if you didn't mind the "clacking" valves, rhoades were "OK". I built a few engines with Rhoades lifters, and for my money, get a custom cam ground for your application, set the cam at "SPLIT" and run it.
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Old 01-19-2012, 10:30 AM
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Quote:
Originally Posted by cusz28
I ran across a magazine from 1965, and in it was an ad for the "Vari-cam". It was a camshaft gear for chevy that advanced and retarded cam timing while the engine was running. has anybody had any experience with this? .
Modern technology today. Used in many of the imports (Acura, Nissan) and mayb some others.
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Old 01-19-2012, 10:49 AM
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Variable Cam timing

But ,In modern cars, ... they do it with the computer, not mechanically, isn't that right , Ritchie???
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Old 01-19-2012, 11:56 AM
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Quote:
Originally Posted by googala7
But ,In modern cars, ... they do it with the computer, not mechanically, isn't that right , Ritchie???
Well, yes. Computer controlled solenoid but oil pressure makes the variable part vary! as in Honda V-Tec
But the princple is the same, it varys cam timing
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Old 01-19-2012, 09:27 PM
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MANY engines today- both import or domestic- have one form or another of VVT/VCT. Even our Impala 3.5L V6 has it. You can feel it come in around 5500 on the way to 7K shift points. That little 3" stroke engine likes to rev.

I grew up w/solid lifter valve trains, Rhodes are no more noisy than a solid cam in a SBC, IMO. If you grew up w/hydraulics, then it may sound odd, at least until you get used to it.

More- Cam Correct Variable Cam Timing
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Old 01-20-2012, 06:14 AM
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Rhoads can work somewhat- like any other hydraulic lifter they are heavily dependant on the liling system. Varicam can work if you have a crank mounted ignition trigger. I don't se the point in the varicam but rhoads lifters may have some applications. IMO you're better off running hyd roller lifters with minimal travel if you're going that route.
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Old 01-20-2012, 06:37 AM
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The whole point of this was to broaden the powerband. And having a computer control the oil flow through the cam-phasing device does do this. But in a single-cam engine, it still can't change the overlap. Assuming you have long-tube headers, yoyur V8 will beform best if it has low overlap and short duration at low RPM, but much more overlap and longer duration at higher RPM.
Moving the cam isn't that helpful, and the Rhoads lifters come closer to the ideal. In practice, they make a larger difference in the modern LSx engine family from Chevy.
It's all about choosing your compromises, and trying to remove them.
But back to broadening the RPM range, and forgetting Honda's V-Tec, Huge improvements have come from combining better-flowing heads with modest cams. This is the opposite of what happened in the '60s. They had poor heads, which limited upper-RPM performance, which they tried to crutch with wild cams, which killed lower-RPM performance. But the wild cam was far cheaper than adding boost, which wasn't so easy back then, either.
And how broad of a powerband do you actually need, anyway? Virtually every automotive transmission out there has ratios close enough that the RPM drop after upshift is seldom greater than 40%. If you're shifting at 6000, then RPM drops to 3600 or more. 3600 to 6000 is not a very broad powerband. Why broaden it?
The goal, of course, is to get a small engine to do the work of a larger engine. There is some merit in the idea, but in practical application it's not such an improvement.
I'd explain further but I have to get to my job before I lose it.
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