The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by Johnny Sweet, Sep 27, 2011.
Never seen one. It uses centrifical force to advance and retard the cam timming?
I have been known to retard my valve timming to gain a little on top. You sacrifice a little on the bottom. Man that would be the exceptional to get it both ways.
That's an interesting contraption. Never seen one before. The little, adjustable cam at upper right would increase spring tension, probably determining the RPM at which the "change" would begin. Also, would probably widen the window of RPM change (wider RATE of change in pre-set total RPM range change) that would take place. Bottom two adjustments should determine initial cam setting and lock on one side, and maximum "degrees" of change and lock on the other side. Theoretically, seems kinda nifty. Probably a bear to dial-in, though. DD
There was another version called Cam-a-go that used oil pressure to advance. There was an old post from someone on here whose father or grandfather made it. I have an old e mail from dmarv on subject so maybe him. Needs crank trigger, though, as you don't want to retard spark at low rpm and advance at high.
I am going to have to call BS on the filters. I am going to call bad mechanics or chinese parts on the needles. Not that any of that has a damned thing to do with the thread.
I don't see any "centrifugal" advance/retard mechanism on this thing. All I see is a spring that will cause the cam timing to jump back and forth a few degrees, and based solely on how much effort it takes to turn the cam. Is it depending on the increased torque required to spin the oil pump at higher RPM's to vary the cam timing?
Ever turn a cam by hand, before it is connected to the crank via gear or chain? It wants to bump back and forth (rotationally) a little every few degrees, caused by lifters putting pressure on the ramps. I can't imaging that this varicam thing would do anything but cause the valve (and ignition) timing to bounce around like a horny cheerleader.
By the way, did you hear about the cheerleader who was on "Are You Smarter than a Fifth Grader"? They asked her what the capitol of Ohio was, and she said "O".
A modern version http://www.competitionproducts.com/Cam-Correct/products/122/
This looks to be a drive that can be manually adjusted to change the valve timing, but I don't think it does it "on the fly".
Spring loaded tensioner, 3 chains with different degrees of stretch and does up to 7 degrees on the fly. Chain tension will increase with RPM and spring loaded tensioner will allow chain to go straighter, retarding cam.
I did some ads and PR for the Vari-Cam. It was manufactured in Phoenix if I recall correctly. It was one of those elusive products that made people feel like they were producing more HP and real documented results were hard to come by. The reference to dmarv was based on the fact that his grandfather, Ollie Morris, did some vari-cam testing on the Offenhauser dyno. I think that Ollie also made some refinements on the original design. Somewhere in the back of my mind, I think that there was a connection between Vari-Cam and Rhodes Lifters.
So really not much different than the VariCam deal, as in both systems it is ultimately a "spring vs camshaft rotation resistance" that determines the variable cam timing.
Is it recommended to then use a crank trigger ignition, or something that can reference ignition timing to the crank instead of the camshaft?
I think back in the day Popular Hot Rodding used one on it '57 test mule at the strip and documented the results.. They had good gains as I remember, but didn't they always...
I think I've got one of these out in the garage somewhere that I bought years ago for a small block Mopar. Think it came from Ed Hamburger's shop, but I never used it. Instead of a cam to adjust the spring tension, I recall it just having a nub cast into the sprocket that one end of the spring rested against.
It also came with a template for drilling two holes into the top of the timing cover and a couple rubber plugs to put in them. With the plugs removed you could reach down inside with a deepwell socket and a long allen wrench and make adjustments without having to tear off the front of the engine. But this might have been an option for the SB Mopars only.
I had forgotten about those, but yes, I remember them.
If effective variable can timing was that simple to do, manufacturers wouldn't employ the more expensive and complex methods they use.
Here's part of an old catalog they sent out to Speed Shops
I remember they bent a bunch of pushrods as valve to piston clearence went away because of cam retarding......
if you still have your varicam , i would be interested ,you still want to sell it
So ... snakeoil ?
They used the fact that the cam required more power the faster it turned. If I remeber right thay were subject to temperature change of the engine oil.
I never paid attention to all the hype back in the day when these were being sold. Don't know if they worked or not, but I picked one up the other day just for the novelty. Now I'll have to look at it more closely to see how it works
The purpose of this device is to shift cam timing to suit operating RPMs. That can provide a fuller torque curve, but not an increase in peak power.
If one of these increases peak power i a race engine that proof the cam timing wasn't ideal before installation.
The high RPM cam setting with a Varicam should be the same as it would be without one. The Varicam advances cam timing at lower RPMs with the intent being increased power at lower RPMs. At higher RPMs it retards to what should be the ideal setting. The only way installing a Varicam could increase max RPM power is if it ended up changing the cam to a more desirable high RPM setting. But, that same setting could be achieved with or without a Varicam.
I don't want to start a mine-is-bigger-than-yours debate about this. You can believe me or not, I understand what I am posting about. An engine doesn't care whether it's in a hydroplane, in a car, or on a dyno, it's not smart enough to know the difference. An engine doesn't care what your dad did, how experienced you are, or what you or I know or don't know. The best cam setting varies with every engine and combination of parts. It's not a matter of knowing all there is to know then applying that to every situation. The only way to know what the optimal cam position is; experiment, then choose what best suits your needs.
I could see a Vericam possibly helping you come off the turns. Like I said, they are intended to improve power at lower RPMs. But max RPMs..... the only way that's going to change with a Varicam is if the max RPM(retarded) cam position was different with and without the device. Which as I said, in your case would indicate the non-Vericam degreeing of the cam was less than ideal for your set-up.
A guy I lived across the street from in college way back when had a near new L88 'Vette with an auto (he only had one leg) and we put in a VariCam to get it to launch better. If I remember correctly we set it for about 5 degrees advance and 0 retard. He thought it improved, but quite frankly I did not notice the difference. It was godawful fast both ways.
Man, do I wish I had that car today . . .
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