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Machining Stock Cams?
- Thread starter DynaSlim
- Start date
It's an old school trick. You're using the stock cam as a core. But no real performance can come about it. Unless it is built back up and reground. But there is issues that can come about.
The only thing done to a stock regrind is changing the ramp rates and maybe a bit of the overlap.
It's like a offset grind crankshaft, "a cheater" more less.
Best bet is just to have a new cam ground from the get go.
The only thing done to a stock regrind is changing the ramp rates and maybe a bit of the overlap.
It's like a offset grind crankshaft, "a cheater" more less.
Best bet is just to have a new cam ground from the get go.
Yes this can be done. Remember, a camshafts lift is the difference between the widest and narrowest part of the lobe. So if you grind away from the narrow part you will effectively have more lift. Also I think you wanna have an engine with hydraulic lifters because they will compensate for the additional lash.
I think you are mistaken, or perhaps not explaining things correctly. Camshaft lift is the difference IN HEIGHT (measured on the centerline of the shaft while "splitting" the lobe in half) between the widest part of the lobe, which is at base circle and the narrowest part which is the top of the lobe. No amount of regrinding in any area OF THE LOBE ITSELF will increase the total lift of that camshaft, though it can decrease lift, decrease duration, or decrease lift while increasing duration.
Sure, if you ground the base circle smaller while leaving the total height of the stock lobe untouched then lift could be gained with a longer length of pushrods to compensate. However, at a point that starts to really upset ramp rates and valvetrain stress forces.
Yeah they sent me that link when they were asking about local shops to regrind their cam.
So basically they need to send out the cam to a manufacturer or save a few more bucks and just order a pre-ground cam?
Can you elaborate on this? The center of the cam always remains a constant and relative to the center of the cam you can not make the lobe any higher with a regrind. You could grind the cam more aggressively and use higher ratio rockers (assuming they're available for a particular car) but you can't get more lift from the same cam. At this point it would be pointless to re-grind a cam rather than to just swap it out for another unless…
With the SHO's we'd regrind the entire cam and then install spacers underneath the lash caps, effectively increasing lift. That's a very unique engine though. I don't even know of another modern day engine that uses lash shims let alone lash caps to hold them in.
You cant gain any lift if you are taking off material by grinding. I can see getting more Duration as long as you compensate with lifters,push rods or valves.
Fellas take a look at the second portion of post #7. I think it will elaborate on the information you are curious about regarding getting more lift out of a reground camshaft.
Pretty much this is the idea. If you look at an SBC crank you'll notice the peak of the lobe is pretty well the height of the bearing journals on the cam its self. I'll see if I have a pic to post up. You've definitely got the right idea, you grind away the sides of the lobe and the base circle leaving the "peak" of it be so that the difference between the base circle and the top of the lobe is larger and hopefully has a more ideal ramp. You then add longer pushrods to make up for the difference. Hydraulic lifters typically only give ~50 thousandths travel, at least in the Chevy world. Not dick in terms of a regrind.
As far as the validity of doing this, it's actually servicable if you've got few or no other options. A few of the 60 degree V6 guys have indicated going this route before. There are a few limitations though:
1)On a cam your surface treatment doesn't go very deep. This means you're likely to run into issues eating the cam at some point, and you can't really harden them easily. Flat tappets being cast iron would likely make this worse. Supposedly rollers hold up a lot better.
2)The LSA is fixed on a SOHC or pushrod style cam. See stuff about peaks of the lobes above. Funnily enough the cam I want to get reground is the "peanut" 179/[email protected] cam GM used in the TBI trucks and low performance TPI stuff that's considered the worse of the worse. The reason being is it has a 109 LSA so it should be a fairly interesting cam with some more lift and duration added.
3)For the reaons above even though you can likely add material to bump the ramp rate up it's plausibly not required.
4)Cam regrinding is not a simple thing, and requires special gear to do. Flat tappets doubly so due to the fact that the lobes aren't flat but designed to make the lifter spin in the bore. It's probably not going to be something "any machinist" can or will do.
Google Delta, they're out of Washington State. I'm also wanting to say there's a shop in Effingham that regrinds cams. These guys may be them. Contact Effingham Regrinding Inc. Effingham, IL
Been meaning to post in this thread again but keep forgetting. It looks like the theory has been explained pretty well but I thought I'd add a few pictures for the visual learners out there. You can see (barely) in the second photo the reground profile in red has more effective lift than the stock profile.
Is this the best way to make power? Not really, but the key is that it can be done on a budget. You can port the cylinder head/s yourself with a dremel tool, have a cam reground for less than 100 bux and then retard it by a few degrees. TRUE Hot Rodding IMO. I'd think you would be able to see a 10% hp improvement on the top end f you did this
Is this the best way to make power? Not really, but the key is that it can be done on a budget. You can port the cylinder head/s yourself with a dremel tool, have a cam reground for less than 100 bux and then retard it by a few degrees. TRUE Hot Rodding IMO. I'd think you would be able to see a 10% hp improvement on the top end f you did this
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