What's the procedure for putting a performance grind onto a steel GMC cam? I took mine to a reputable cam grinder. He did a hardness test, roughed out the cam, then another hardness test. It went from Rockwell 57C to 26C. Now he won't grind it as he says the process of nitriding, straightening, and polishing will be too difficult. Wants me to locate an iron cam. How is it that GM could manufacture these by the 1000s without issue, but it's too difficult to do a one off? Is there some secret to the process? Are there other options to hardening, e.g., spray welding with hard facing? Do I need to find someone else to grind my cam? If anyone has a good iron cam core, shoot me a PM. It will be hard to find one in NZ. I'm quite sure all the GMCs here are ex-military and have steel cams.
I've had chevy 235 cams reground at Schnieder here in San Diego. They even refaced my lifters, 0 problems
You do not want an iron cam, the steel cam is the good one. When you go to a cam grinder you are paying for a finished product. if the current grinder does not know what to do find someone else.
Have you talked to Adrian at Franklin Cams? I had an old solid lifter cam for my 324 rocket motor and he reground it to suit hydraulic lifters. Don't ask me what was involved there.
I'm pretty sure the other options are available, not everyone however has those options available to them, and for that reason it's make an excuse to avoid saying so. 26C...sound like it changed into aluminum. You might have to send it to India, I hear they do wonderful things over there with very little.
I did some googling because of this post, I’d always assumed a reground cam was also hardened again. I couldn’t find an answer, but I did see that cams are case hardened, I didn’t dig into that, but isn’t case hardening.002-.003 or so deep? If so, wouldn’t any reground cam need to be hardened..some links mentioned “hardened on soft cores” so the cam wouldn’t be brittle, but that’s internet findings…. @Pete1 does reground son Flathead cams (among others I guess) maybe he can add? I know, this doesn’t help the OP, but thought an appropriate question to ask in this this thread since Pete is a member.
I've seen some really wild stuff on YouTube of Indians and Pakis welding broken truck axles and crankshafts. I'm glad I don't have to drive on their roads. Kiwis were once amongst the best bush mechanics in the world, which is why at one time they were found on every Formula 1 team. These days the good ones are all retirement age and getting harder to find. I'll stick to my locals, thanks! There's a place that does Thermal Spraying about 5 minutes from my house, I'll talk to them next week and phone some of the other grinders. I wonder if Hard Chroming is an option? I need to be careful of the oil pump/distributor drive gear. It could turn out either too soft or too brittle if heat is involved. I have a new bronze distributor gear.
Typical case hardening, known as carburizing, is about 0.030 inch depth. Can be little less, but usually in that range. Has to be done at red hot temps, so distortion is an issue, beside the fact that the red hot temps will eliminate any previous heat treatment of the part. Nitriding is very thin and only 0.002-.003 inch depth. That may be what you are thinking. Nitriding is done at lower temps like 900-1000F where distortion is not as much of a problem.
Maybe,...Larokee on this forum bought my 37 truck with a modified 302 GMC..The cam was an NOS cast iron reground to a fast lift tight lash by the late Lazer Cams....Larry said the engine had 80,000 miles when it devoloped a headgasket leak....The cam lifters showed no wear..The flat tappets were from Pat Dykes before folded.. A roller cam needs to needs to be steel....
I was told iron cams are hard all the way through, steel cams are case hardened, which is why my cam is soft after roughing out. Iron cams do not need hardening after regrinding. Nitriding needs a lot of heat, which apparently warps the cam, but is also abrasive and needs polishing.
"If it were easy, everyone would be doing it." Well, maybe not everyone, but if you got the cash, why not.
I am running a new production ISKY in the 261 in my 53 I have never had an issue. Also in the 261 in the Model a Stock car. I find ISKY to be very helpful as well.
All the 235 and 261 cams I have are iron. My GMC has bucket type lifters which are the same as 39 Chevy 216, so I assume 39s had a steel cam? You have to be careful not to mismatch lifters and distributor gears. My bucket lifters can be refaced, but does anyone know the correct replacement milk can lifter for steel cams?
I was originally going to take the cam there, but got talked into going elsewhere. I'll call him next week. Is your cam steel or iron?
I have had two GMC cam grinds done at Delta in Tacoma that both had issues (lifters stopped rotating) . . . then switched to Oregon Cam Grinding in Vancouver, WA . . . they fixed the cast iron Delta Cam for me, and also ground several cams for my GMC buddies . . . very happy with a snappy engine performance and quieter valvetrain that doesn’t need adjusting nearly as often as the Delta cam grind required.
Lifters must be ground with the correct radius in order to rotate. If I have to buy an iron cam ex USA, I'll get it shipped to a cam grinder before shipping to NZ. What about Schneider's? I'm looking at something like their 264-74F grind.
Iron and steel wear differently. Both come in different grades. Iron is often a little softer than steel but more abrasive. I would look for some sort of a steel replacement lifter, as cast iron lifters will most likely cause premature cam wear on a steel cam shaft. Now just to clarify an earlier statement. When we are talking old pieces we are not talking "Billet" steel cam shafts. A cam shaft from the era of motors that we normally use is a forging. A billet cam shaft is an entirely different monster. The reason I am saying this is not to prove how smart I am. I am just trying to separate modern technology from what we should be talking about. In the whole scheme of things I am probably not real smart at all. There is a minor problem that separates a "steel" part from a cast part. Iron or cast parts have a tendency to have air pockets and fissures more often than forgings. Another thought here is that the face of a cam shaft, as well as other wear parts get the surface hardness by burnishing. When you regrind a cam shaft or a crank or a writs pin and etc. you grind that surface hardness off. That is the reason for proper cam break in, also the reason that you can run a flat tappet cam for 150K plus without cam failure. . . better stop here before I become even more offensive.
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