I hear of people needing blanks and whatnot and needing a regrind or that is not available for that engine. Why can't they just make one and grind to specs? Are cams made of some special type of metal or something. The reason I'm asking is that I was told i could not get a good cam for my 337 Linc but I would have to get a regrind. Why not just a blank ground down to spec. Please explain this to my stupid ass.
The short answer is because there aren't 'blanks' available for every engine that's out there anymore. Some engines (like your Lincoln) probably never had an unground blank available for a custom grind, and would have had to use a re-grind for a performance build. Some of the more popular engines out there have unground billets (both cast and steel) available "off the shelf" for grinding to suit performance use....but for a lot of vintage engines, you are stuck with a regrind. Also, this may be common knowledge, but I'll type it anyway: No two families of engines share the same cam specs in regards to overall length, journal placement and diameter, lobe size and placement, distributor gear, etc....so you can't take a Small Block Chevy billet and grind it to fit a 337 Lincoln either. As far as just making a billet blank goes...there are a few guys out there that can CNC a steel billet for pretty much any engine. But for most cases it would be cost prohibitve to set it up for a short run. There is nothing wrong with re-grinding a cam to get the profile that you want as long as you have a core that allows you to get where you want to go. Some cams are limited in the amount that you can change the lobe center, duration, and lift because of the amount of 'meat' that is on the lobe. Usually a reground cam will have a reduced base circle, because material is ground off the opposite side of the lobe to increase lift, etc. Also, billet cam cores normally cannot be significantly re-ground because the surface hardenening is only so deep. Cast cam cores on the other hand are typically either parkerized or through-hardened and can be re-ground without danger of going through the hardened surface. One other thing worth mentioning (for OHV engines) is that if you don't have an adjustable valve train, you will need adjustable pushrods for most motors with a reground cam...because of the reduced base circle. Of course if your cam is hydraulic, you can usually find a standard pushrod length that will work for your application by using an adjustable pushrod to check the length that you need.
Cam cores are cast very close to their final shape. They are then ground for the bearing surfaces and final lobe profile. Very little metal is actually removed in this process. That is why Elgin or Mondelo can sell you a stock replacement cam for under $100 Grinding one out of a billet requires a tremendous ammount of grinding, and prices start somewhere around $500. Re-grinding a cam is an option, as a new lobe profile can be carved out of the existing core, but some issues arise from this. Spacifically, the base circle must be reduced, nessecating longer push rods, or special lifters. If you got the $$$, you can have anything you want. If your just a regular schmo, your options list gets short pretty quick.
If a guy wants to really mix things up, such as significantly increased lift and changed lobe centers... what about welding up the lobes with hardface material, straightening the cam billet (I've seen cam guys hit 'em with an air chisel w/ a blunt tip) and grinding it? I know Crower does/did offer hardface as an option on their cams... Probably not worth doing for a common engine such as SBC, 440 MoPar, but what about the guy who's just dead set on building a killer MEL? -bill
Then you'd have another issue when it came time to find and buy chilled iron lifters to go with the hardface cam. They're just not easy to get for any engine, much less an 'oddball.' How easy is it to find adjustable lifters for a 337 Lincoln Flathead anyway?
Bass pretty well said it all. In the "back when" days the majority of hotrod cams were regrinds. You either traded in your cam as a core or had it reground to the specs you wanted. I'd also go along with the concept of finding the right adjustable lifters if they are even available before doing any grinding on the cam.
I'm in the middle of building the flathead six Mopar for my HA/GR, right now I'm dealing with cam "issues". the particular grind I want to run is "tight" according to the grinder, and requires an EXTRA NICE core. I am going to buy an NOS stocker cam and send it to him to grind. Don't be afraid to have your good core ground- just make sure you use a reputable grinder, I'd hate to get stuck looking for a replacement if yours got "lost"
If you have the bucks Joe Panake at Roto-Faze will make you a blank. If you can live with a blank that has no gear on it they are not completly out of site. On my Plymouth the distributer drive gear slides on the front like a '49 Ford and I ran a belt driven external oil pump. Not easy.
Aren't 337 truck engines equiped with adjustable lifters? Independent Cam grinders are almost extinct. The big guys are way to expensive. I had all my cams made at www.berrycam.com They do lots of tractor pull cams. In the 1980's they made Camshafts from scratch for me when I built all the OHC conversions with variable valve events. Its quite an experience to build a camshaft and design the lobes etc. Its really not that big a deal if you have a degree wheel and a dial indicator. We prototyped in plastic and then moved into brass. The trick is to make the lobes about 1/8 of an inch wide so they are easy to file yet solid enough to fit in the lobe copying mode of a cam grinder.
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