I do have a casting pattern and 3 cast steel prototype roller camshaft castings... and no "good" way to hob the OP gear.
DD
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| Author: | Doc [ Tue Jun 07, 2011 4:49 pm ] |
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I do have a casting pattern and 3 cast steel prototype roller camshaft castings... and no "good" way to hob the OP gear. DD |
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| Author: | CNC-Dude [ Tue Jun 07, 2011 4:54 pm ] |
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I think the person you spoke to misunderstood what you were asking them. A flat tappet cast iron camshaft cannot be made compatible with roller lifters at all. Thats the main reason they are made from an extremely hard and strong billet steel(8620), that when its heatreated is over 60 Rockwell in hardness( like a bearing race). The roller wheels in the lifters are also the same steel type and hardness and would rub the lobes right off of the much softer cast iron camshaft almost immediately. That coupled with the much higher spring pressure required by roller cam lobe profiles to function would also make the cast iron flat tappet cam fail almost immediately. |
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| Author: | sandy in BC [ Tue Jun 07, 2011 5:45 pm ] |
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Quote: the person I talked to said they have, and a member on this forum has been running it for 2 years..
..............it goes nicely with my prototype aluminum head.
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| Author: | Joshie225 [ Tue Jun 07, 2011 5:52 pm ] |
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Yes, Oregon Cam Grinding has put roller profiles on stock cam cores. The aggressive cams which were used for racing do not live very long. The milder one(s) for the street do live longer. Someone would need to get in touch with the person running said cams to get the final word. Me, I'm staying flat tappet. |
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| Author: | USAJon [ Tue Jun 07, 2011 5:52 pm ] |
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yep..musta made a misssunderstanding. we will drop it. ps I do know the members name . so... |
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| Author: | CNC-Dude [ Tue Jun 07, 2011 6:16 pm ] |
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I think im seeing what you are saying. It is a flat tappet cam with a more aggressive profile ground on it similar to a roller cam. This doesn't make it a roller cam....however, its still a flat tappet cam. When you said you asked them if they could "grind for a roller" really didn't make any sense. It was implying that you were going to be able to use roller lifters on a cast iron flat tappet camshaft and were somehow going to be creating a roller cam out of it, and that can't be done from the reasons already mentioned. |
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| Author: | Joshie225 [ Tue Jun 07, 2011 6:21 pm ] |
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But that's exactly what they have done. Oregon put a roller profile on a stock cam core and the end user runs roller lifters on said cam. The aggressive ones don't last long, but what do you want? Oh, that's right, you want to split hairs. Enjoy! |
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| Author: | CNC-Dude [ Tue Jun 07, 2011 6:43 pm ] |
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I was just trying got get a handle on what USAJon was saying he asked the cam company he mentioned, because it wasn't making any sense in how they were grinding a flat tappet for a roller in the way he was describing it. No hair splitting at all. |
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| Author: | runvs_826 [ Tue Jun 07, 2011 7:14 pm ] |
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So the question I have is how did Chrysler grind the op gear? Was it a function like threading with a tool post on the lathe? I would assume this is how they do the initial cut on the lobe? Just wondering even if I never attempt this stuff. Do you have anyway of casting said cams Doug? Do they have meat there to do the op cutting? |
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| Author: | CNC-Dude [ Tue Jun 07, 2011 7:43 pm ] |
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The task of hobbing the OP gear was actually done by whichever/whatever company made the camshafts for Chrysler. It can be done in a CNC lathe that has "live tooling", or a CNC mill with 4 axis capability. In the old days it was done in a Bridgeport style mill with a fixture(hobber) that rotated the camshaft incrementally as it moved the work table at the same time to create the helical cut. |
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| Author: | runvs_826 [ Tue Jun 07, 2011 8:02 pm ] |
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So they had a pig roasting thing on the mill? What is the benefit than something attached to the lathe I wonder? So does the turning device grab the cam from both sides? |
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| Author: | CNC-Dude [ Tue Jun 07, 2011 8:12 pm ] |
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Yeah, the pig roasting idea is a good way to compare it. I think the hobber was designed to be used with a milling machine originally. It supports the cam at each end and its held between centers. If you have ever noticed the countersink at the rear of the camshaft in the center of the cam body, and the one at the front or threaded hole. These are also used to index and grind the cam in the camgrinder as well. |
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| Author: | DusterIdiot [ Tue Jun 07, 2011 9:23 pm ] |
| Post subject: | Ka-chang! |
Or was it 'Ker-Chow'.... Quote: Oregon put a roller profile on a stock cam core and the end user runs roller lifters on said cam. The aggressive ones don't last long, but what do you want?
Most cam places can grind a stock cam core to most profiles you want...but you have to agree to a couple of things: 1) It's a test cam not to be run in a car, 2) If you do decide to run it, the cam company isn't liable for failures/damage/anything to do with this misadventure....  Once you are able to calm them down and assure them you aren't some kind of escapee from the L-head funny farm...and after you find out that they have indeed ground a couple of "test cams" for another racer in the not so local area...and don't mind spending a few $$$ to have the base circle greatly reduced on your old worn out 1974 225 cam blanks, that were just laying around...  They might grind you one of their true roller lobes on an old flat tappet core...  Which definately is a bit radical for a flat tappet....  But seems to be about right when compared to a lifter out of a 5.9 Magnum  Besides Doc, there is one racer in our area that has done this and OCG made the cam for him, he did divulge the cam has lasted for a few years...but...his car is strictly race and has no street time, he has it towed to and from the lanes and fires it up only as needed or when called to the line... I'm fine with staying flat tappets, but I won't argue with a guy running 5-6 seconds faster than me...(of course when you are at the drags and some of the really knowledgable individuals start talking about things that start you down that path...you have to decide whether you are going to follow the rabbit or not...I have an engine block in the corner that says "build me"....It's going to be called Alice I think...  ....)For all the reasons listed: the stock cam is soft and won't take repeated abuse from the rollers under high pressure springs...this opens the debate for using lower pressure springs (which might limit RPM due to valve float...but some of us have run flat tappet cams at 5500 rpm with only 30-50lbs of spring tension and not known it)...or might open the idea of using a hydraulic roller. Oiling the lobes is paramount, so a spray bar would be required...and probably grooving the lifter bore for insurance. The cam can be austempered or chromed...but the cams base metal being soft, it will eventually collapse like tarmac with the dirt washed out from under it... Shot peening or surface compression might build up a more solid layer on the lobe face...but still even under that, the metal is soft and will buckle as well... Now everyone is somewhat caught up on the field...time to put the CNC guys and wintertime tinkerers to work....  -D.idiot |
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| Author: | runvs_826 [ Tue Jun 07, 2011 10:23 pm ] |
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So a cast camshaft even with some hardening isn't even really worth it cause you still need a way to cut the op gears? So, a billet camshaft is definite the way to go, and you can just use pre existing roller tappets from a v8. I'm glad someone brought this old thread up you learn stuff you take for granted by just going to summit racing and clicking on parts. |
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| Author: | CNC-Dude [ Wed Jun 08, 2011 1:05 am ] |
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Quote: So a cast camshaft even with some hardening isn't even really worth it cause you still need a way to cut the op gears?
Even with a billet steel cam blank, the OP gear will still need to be machined into the cam. Also, a cast cam was never meant or designed to be used with roller lifters. The first roller cam was designed by Chet Herbert over 50 years ago, and were billet steel, and that has remained the industry standard for this long for a reason. For over 20 years now Ford and Chevy have had hydraulic roller cams as OEM items on most all their engines, and Chrysler has as well. They even come with a 100,000 mile warranty today, so there is nothing to be leary or skeptical about as far as reliability goes. Most of the horror stories you here about roller cams being unreliable or troublesome are from the incorrect use of other components not meant to be used in conjunction with this type of camshaft. If your valvetrain is set up to be used this way and all other parts are made and designed to be used with a roller cam, then you will not have any problems. The key being make sure you use correct valve springs, retainers, valve locks, pushrods, rocker arms, etc... for the right cam you are using.
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