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Old 04-22-2009, 02:12 PM   #11 (permalink)
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You might also be interested in "The Soft head" which makes it's mention in "Talking heads" as well.

IIRC *it's been awhile, I need to refresh* "The Soft head" deals with the type of cam/head system that Comp was using in the 1980's on NASCAR engines, which was (again, IIRC) basically an atkinson-type cam with a slightly different profile, which allowed for insanely high static compression, (18:1 and more), without detonation, on the gas that they used back then, in a carb'd engine.

Something you probably won't like about Larry, as most don't, is his "that's old technology, let go of it" attitude. Anything that is a barrier is old technology. He finds ways to break it down.

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Old 05-01-2009, 04:54 PM   #12 (permalink)
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Quote:
Originally Posted by Daox View Post
Not nearly being a cam expert, I really have no idea where I'd start. Would a normal cam regrind shop be able to do this? I'm thinking it would be well out of their scope. Performance shops usually know squat about efficiency enhancements.

Also, your method would require welding on additional material I assume. I've heard some bad things about running welded regrinds, but I'm sure they can't be that bad. On the other hand, my idea only includes grinding. Yours obviously would provide larger FE gains, mine would be cheaper although I don't have any idea how much cheaper.


Thanks for the info on the magazine articles Christ. I assume I can get those online somehow? I checked Hot Rod's website, but I couldn't find where I could get old articles.
We've been regrinding cams since 1970 here at Kams, Inc. in Oklahoma City. Welding a cam lobe requires different procedures and materials depending on the material the lobe is made from. Some cam designs are also difficult to weld. However, it can be done with the proper techniques. A properly welded and ground cam should last as well as the original did.

Kams, Inc. camshaft regrinding, design, and manufacturing for industrial engines
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Old 05-06-2009, 10:13 AM   #13 (permalink)
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I am looking further into this option. I'd really love some suggestions on cam regrind houses people have used and can recommend.
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Old 05-16-2009, 02:26 AM   #14 (permalink)
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What might be of more interest to you. . .

If you increase the valve surface area opposed to volume you get a much faster intake. So if you have 2 square inches in one big valve you get x periphery surface area to the valve(which is the only area that can feed the cylinder). If you cut the valve size in half you have same area more periphery surface area and faster loading of the cylinder.

You have 4 valves and limiting the opening does what rk said and just limits your available power forcing you to drive more economically because its physically impossible for you to do different. If you can find a header with 5(3 in 2 out) you can achieve your late stage loading without sacrifing volumetric efficiency.

Downside is they are more complicated and very expensive if you wreck your timing belt. . .
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Old 05-22-2009, 06:08 PM   #15 (permalink)
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I could be wrong, but I believe atkinson cams would require a complete engine remap/retune. That's not something i'd be comfortable doing without a LOT of access to a dyno and high octane fuel.
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Old 05-22-2009, 11:06 PM   #16 (permalink)
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Quote:
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I could be wrong, but I believe atkinson cams would require a complete engine remap/retune. That's not something i'd be comfortable doing without a LOT of access to a dyno and high octane fuel.
All things considered there shouldn't be enough difference to warrant high octane fuel since the effective compression ratio should be pretty low.
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Old 05-22-2009, 11:10 PM   #17 (permalink)
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All things considered there shouldn't be enough difference to warrant high octane fuel since the effective compression ratio should be pretty low.

I'm more concerned that you accidentally run it lean when your retuning, which is something that promotes heavy knocking. Standard operating procedure is to run race gas (110 octane) when you are tuning a car.
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Old 05-22-2009, 11:21 PM   #18 (permalink)
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It'd be nearly impossible to run it lean since an Atkinsonized cam should let in less air during open loop WOT/idle. Closed loop would be no problem, just the equivalent of running from 0-whatever% load given the new cam profile.
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Old 05-22-2009, 11:33 PM   #19 (permalink)
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It'd be nearly impossible to run it lean since an Atkinsonized cam should let in less air during open loop WOT/idle. Closed loop would be no problem, just the equivalent of running from 0-whatever% load given the new cam profile.
Assuming you have full access to the original factory tune, then you would be fine, and you'd be able to lean it out in small steps to get her back into tune. Most of the time, my experience is that this isn't possible.

If you just threw the cams in and ran the original program stock, the car might run like crap. It'd be running rich until the O2 sensor warmed up, and the spark curve would be off. Even though cars now have a MAF system it is only used to adjust steady-state fuel-trims. Cars still rely on the speed-density charts system for a baseline. With a new cam, that baseline is going to be off.

Of course this only applys if the cam your putting in is aggressively different. A few degrees here or there, and the general correction coefficients would take care of everything.
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Old 05-23-2009, 03:03 AM   #20 (permalink)
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For aggressive cam changes I was thinking w/ MAP it wouldn't be a problem, but w/ MAF we would need to change the tune or maybe have a little black box that scales back voltage proportionally to how much less air is let in.

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