I'm using a Howards Cams 220235-12 roller cam in my 351W roller block. I'll be using a stock Duraspark dizzy. Is it necessary to change the stock dizzy gear to some alloy gear?

 

Looking at the picture on like it is tough to tell but it all depends on what core Howard's used to grind the cam. If its a SADI core then you should use a stock cast iron gear. If it is a steel core you'll have to use a bronze, a steel or a melonized gear for compatibility.

A SADI core is cast iron other cores are steel and can be carburized (copper plated barrel) or induction hardened(barrel will be un plated) and can look black or just a steel color.

 

I used a stock gear on a custom SADI camshaft and still had my gears eat each other. Two things that I learned from that were to ensure that the end play on your distributor is within specs, and put a 1/32" hole in the oil galley plug which is directly behind the distributor gear. My second custom cam, I ordered billet and a steel gear, due to the issues with manufacturers were having with SADI cores, and I took care of the end play and the oiling issue. This cam has lasted almost 3 years and appears to be wearing fine, but I can't tell you if it is the billet core, the other fixes; or a combination of the two that is keeping it alive.

 

Someone else installed the cam, I do recall the black coloring on the cam body. Thanks for the reply.

 

Thanks for the info, I will be changing gears.

 

I can't think of a SADI that I've had a gear problem with in a Ford but anything is certainly possible. The biggest problem I've seen with the SADI cores has been in small block Chevy engines where it would wear the fuel pump lobe. I've fixed that by regrinding it then they switched to a bronze tipped rod. So far, so good.

 

I've read a lot of your replies to other posts. This seventy four year old is definitely getting schooled on the unknown. Thanks again.

 

I do think that if there's a Ford that's going to give gear trouble the 351W is probably the most likely. That engine uses an oil pump with the same rotors as a 460 yet it still has the small gears like a 289. It puts quite a bit of load on the gear especially if someone puts in a high volume and or high pressure pump.

 

I have read of others having issues with their gears getting eaten and had others tell me the same. Some blame overseas manufacturing, but I'm guessing that in my case, it very well could have been the distributor being too loose. Ed Curtis at FTI recommends the 1/32" hole in the galley plug, so I followed that advice and fixed the distributor. The cost to purchase a billet was about the same price as another SADI, so I chose to go that route for my peace of mind. I did bother me that I have installed several flat tappet cams in various engines and never had a failure, and my first roller cam install only lasted a few thousand miles tops. And I will agree, Dave is one of the few that you know that he knows what he is talking about.

 

One of the things that I don't really understand is how two different pieces of metal can run together with a lubricant and be compatible, run indefinitely with little wear yet other combinations will fail almost instantly. Most of the time the way it tends to work is one piece needs to be harder than the other one by a few points Rockwell C to make them compatible. If they are too close to the same hardness wise they can start to weld together, tear off metal and fail. Flat tappets work this way and the lifter is harder than the cam lobe. From what I've seen in my own testing flat tappets will check between about 57 and 63 Rockwell while the cams will be down around 52 to 55C.

Cams are a difficult heat treating problem. While the lobes are hardened the barrel is not and this holds true for flat tappets as well as rollers. The reason for this is because the barrel has to remain ductile to keep it from breaking. This selective hardening goes for the gear surfaces too. I've never Rockwell tested a gear on a cam but it would be tricky but interesting. This selective heat treating is also why the cam is easy to machine in a lathe to repair a center or drill and tap a bolt hole. As long as you are in the barrel it is no problem to cut.

I appreciate the complements and I do have a lot of information that I like to share. I spend every day repairing engine parts, taking what is often useless junk and making it good again. When doing work like I do I think that it is very important that the customers' projects go well and give good results and if that means that I have to give out information for free that's ok.