Re-grinding a cam, educate me please

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mad dog

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Good morning FABO.. I want to build my 340 to 1968 4-speed specs, Rusty has me very interested to call Oregon cam and order that very cam. Here is where im confused on re-grinding an old cam to new specs, how do they do that?
AM i better off ordering a new cam from Oregon or can they re-grind my old cams that i have in the attic, one is a 69 and one is a 70 cam, I keep hearing that the old metal is superior to the metal that they use today. obviously im not educated and im hoping FABO can help me out. I will also need lifter recommendation... any help or advice is always appreciated...Rich...@rustyratrod
 
They can regrind the old cam just fine. They can manipulate the lobe anywhere on the cam core they want. They do that by moving the base circle. Mopars normally require a longer pushrod to make up for that difference. No big deal as pushrods are pretty cheap. I also agree with using the old cam core. According to Ken at Oregon, they are hardened pretty much all the way to the core. I'm not sure a new one would be hardened that deep.
 
I too am curious of the procedure. I am guessing they weld more material on the lobes and regrind. Just guessing. I'm sure someone will chime in.
 
Kendog 170 said:
I too am curious of the procedure. I am guessing they weld more material on the lobes and regrind. Just guessing. I'm sure someone will chime in.
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No sir. They regrind the lobes on a smaller base circle effectively increasing the lift. They can "move" the lobe pretty much anywhere on the cam core they want.
 
RustyRatRod said:
They can regrind the old cam just fine. They can manipulate the lobe anywhere on the cam core they want. They do that by moving the base circle. Mopars normally require a longer pushrod to make up for that difference. No big deal as pushrods are pretty cheap. I also agree with using the old cam core. According to Ken at Oregon, they are hardened pretty much all the way to the core. I'm not sure a new one would be hardened that deep.
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You be me to my last post. lol
 
Picture a V8 cam shaft. It has 16 (changed from the erroneous 18) separate 'cams'; 8 for intake and 8 for exhaust. One side of each cam is a smooth round circle ( this is the bottom of the base circle), and the opposite side (lobe) has the big bump that pushes up on the lifter. Lets say that your cam had an intake lift of 0.445" when new. That means that the tip of the lobe is 0.445" above the base circle. Lets also say that after 100,000 miles the lift is down to 0.440" due to wear. So the cam now has 0.005" less lift than before. A cam re-grinder does not need to add material to the lobe. Picture having a machine that can accurately grind 0.005" off of the base circle side (leaving it as a smooth accurate circle) and leave the lobe side alone. You now are back to having the tip of the lobe 0.445" above the base circle. That is a gross oversimplification, but the overall idea is correct. They will actually need to grind a little more than 0.005 off the base circle side because they do need to work on the lobe side a bit to restore the correct duration. Once the cam has been reground, the tip of the lobe will be 0.445" above the base circle, so you will have 0.445" lift. However, since they had to grind down the base circle side, that means that a micrometer measurement of the cam from the tip of the lobe to the bottom of the base circle side will be less than it was before. So you may very well need new pushrods.
 
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harrisonm said:
Picture a V8 cam shaft. It has 18 separate 'cams'; 8 for intake and 8 for exhaust. One side of each cam is a smooth round circle ( this is the bottom of the base circle), and the opposite side (lobe) has the big bump that pushes up on the lifter. Lets say that your cam had an intake lift of 0.445" when new. That means that the tip of the lobe is 0.445" above the base circle. Lets also say that after 100,000 miles the lift is down to 0.440" due to wear. So the cam now has 0.005" less lift than before. A cam re-grinder does not need to add material to the lobe. Picture having a machine that can accurately grind 0.005" off of the base circle side (leaving it as a smooth accurate circle) and leave the lobe side alone. You now are back to having the tip of the lobe 0.445" above the base circle. That is a gross oversimplification, but the overall idea is correct. They will actually need to grind a little more than 0.005 off the base circle side because they do need to work on the lobe side a bit to restore the correct duration. Once the cam has been reground, the tip of the lobe will be 0.445" above the base circle, so you will have 0.445" lift. However, since they had to grind down the base circle side, that means that a micrometer measurement of the cam from the tip of the lobe to the bottom of the base circle side will be less than it was before. So you may very well need new pushrods.
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Almost correct. .444 is at the valve after the lift of the cam has been multiplied by the rocker arm ratio.
.296x1.5=.444
Okay I see you're just using 450 as a number for an example I just got excited.
 
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OK, not sure why you are asking us, why not call Oregon Cam. The way they really regrind a camshaft is first you pick a lobe that will fit with the material left on your used cam lobes. You can only "adjust" your angles, lobe separation, so far since you need to hit solid metal when you grind the new lobes. They regrind the new lobe with a smaller base circle to get the lift and duration desired. Again, you can only go so far, since you need metal to make the new lobe. Since the base circle is smaller, you may need different length pushrods. This is a simplification of what they really do. You can weld lobes to get most profiles, but I imagine that gets costly quick.
 
66fs said:
OK, not sure why you are asking us, why not call Oregon Cam. The way they really regrind a camshaft is first you pick a lobe that will fit with the material left on your used cam lobes. You can only "adjust" your angles, lobe separation, so far since you need to hit solid metal when you grind the new lobes. They regrind the new lobe with a smaller base circle to get the lift and duration desired. Again, you can only go so far, since you need metal to make the new lobe. Since the base circle is smaller, you may need different length pushrods. This is a simplification of what they really do. You can weld lobes to get most profiles, but I imagine that gets costly quick.
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No, they can regrind a stock hydraulic flat tappet into a .650 lift solid roller. As long as there are no wiped lobes, the sky's pretty much the limit.
 
66fs said:
I depends on how small you want the base circle and the desired lobe.
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I've seen base circles smaller than the core itself. Not optimal, they are more like a cheater cam, but it works. As long as the pushrod length and valve train geometry is correct, there's no harm done.
 
The last time I called Oregon cam, I was told they can only adjust LSA as much as the core will allow. Which, for the cam I wanted, couldn't be done with the stock roller LA cam I had because the LSA was too wide on the stock cam.

He also cautioned against grinding too much because it'd be going past the hardened layer, even though the majority of the grinding was on the base where surface hardness may not be as big of a deal. The cam I wanted was only 240*@.050" and .560" (.350" lobe) on a 108 LSA.

Either way, he made it clear that there are definitely limitations to how much a stock cam could be re-ground or how much the LSA could be adjusted.
 
mopowers said:
The last time I called Oregon cam, I was told they can only adjust LSA as much as the core will allow. Which, for the cam I wanted, couldn't be done with the stock roller LA cam I had because the LSA was too wide on the stock cam.

He also cautioned against grinding too much because it'd be going past the hardened layer, even though the majority of the grinding was on the base where surface hardness may not be as big of a deal. The cam I wanted was only 240*@.050" and .560" (.350" lobe) on a 108 LSA.

Either way, he made it clear that there are definitely limitations to how much a stock cam could be re-ground or how much the LSA could be adjusted.
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That's correct on the LSA. It cannot be adjusted too much. The LSA is the big limiting factor. You CAN change it a good bit, but you won't be left with much of a base circle at all. lol
 
mad dog said:
Good morning FABO.. I want to build my 340 to 1968 4-speed specs, Rusty has me very interested to call Oregon cam and order that very cam. Here is where im confused on re-grinding an old cam to new specs, how do they do that?
AM i better off ordering a new cam from Oregon or can they re-grind my old cams that i have in the attic, one is a 69 and one is a 70 cam, I keep hearing that the old metal is superior to the metal that they use today. obviously im not educated and im hoping FABO can help me out. I will also need lifter recommendation... any help or advice is always appreciated...Rich...@rustyratrod
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youtube has a bunch of videos explaining it.
 
guys like i said im not very versed on cam stuff, i dont want to take my stock 1970 used cam and try to regrind a monster cam out of it, there probably isnt much of a difference between a 69-70 cam and a 68-4 speed cam...???
 
66fs... your not sure why im asking the FABO community???? i thought this was a mopar car forum where you can ask questions?
sure i can call Oregon but i thought i could ask the knowledgeable people here first... if answering my dumb questions are a hassle for you just move on... thank you to everyone else...Rich
 
if it were me, i'd send my old core in and have it reground by them and save a bit of money, and if you have lifters i'd do the same with them.

you're not wildly changing anything specs wise so it'll be no problem for them to regrind. besides, what are you going to do with those old cores? make a lamp of of 'em?

if you need new lifters, there's a lot of choices besides comp. i've been using melling for quite some time and been happy with them.
 
mad dog said:
66fs... your not sure why im asking the FABO community???? i thought this was a mopar car forum where you can ask questions?
sure i can call Oregon but i thought i could ask the knowledgeable people here first... if answering my dumb questions are a hassle for you just move on... thank you to everyone else...Rich
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Why not go to an expert. Oregon Cam, Racer Brown, and others will take the time to talk to you. They really know what is possible and know the capabilities, benefits, and shortcomings of what you want to do. You saw the posts. Do you know who is right or wrong? You can ask any question you want, as a matter of fact I answered you with the correct information. No hassle I only chime in to help. Sorry to bother you Rich.
 
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Last cam I had reground was a 63 pontiac trophy 4. Sent two cores t o Effingham Regrinding Effingham Illinois they did a great job on them and if you have ever had anything to do with half of a 389 they must be right or they will vibrate.
 
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