I'm about to put a cam in with press-on gear. But it came with some sort of plate that goes in front of the gear and is held by a screw into the end of the cam. It's a Scheid. Anyone familiar with them?

 

Did you use your stock gear from the old cam or did they send you a different gear?

 

Don M
RonA
Thank you both for your input.

 

So aint it safe to buy an used PDR cam with press on gear?
for a 215 engine, and yeah it has some more rack travel then normal.

what does more rack travel affect gear walk?

what exactly happens when the gear walks?

 

Rack travel increases the HP required to drive the pump and the unit time the load is applied.

Once the gear begins to walk forward the leverage on the nose of the cam increases. The gear is now further forward and has more force on the nose, making it easier to snap the cam.

A large percentage of cams break at the number one bearing journal. Depending on when and how it breaks, the rest of the cam can come apart as well.

Vp44 and CR engines are much less vulnerable.

 

Should i refuse buying a used PDR cam? from someone who switched to other brand?

its cheap in my opinion, and can i just swap the cam? or do i have to change anything else? lifters and stuff?

 

I haven't installed the cam yet. I was going to replace the gear because I was worried about my old one failing on me.

 

FWIW The guy who bought my truck had a Schied cam fail on him in a different truck. It snapped at the second journal when he punched it running down the highway. It took the crank, most of the rods, pistons and valvetrain with it. At 4000 miles, Schied said "tough luck, it's a racing app. we'll sell you the same exact parts at cost if you want to rebuild it with Schied parts." He went with a different vendor for the rebuild.

brandon.

 

Ouch
So has there been any failures with the bolt on style gear?
Is it just not discussed or...? But I dont recall ever hearing of this being a problem with the stock cam. I'm sure there are more stock cam trucks than ones with replacments?

 

I have never had a failure of a bolt-on cam. No breakage ever. Knock on wood!

That being said: Performance parts like a cams, pistons, injectors, or anything you can bolt on that is intended to enhance performance will never be 100% free from failure. Knowing that, the person or people that put the parts to market have a responsibility to do the best they can to insure failures are not going to happen. Since performance companies are basically immune from recourse, many of them just sell stuff and hope for the best.

I have used the forums 4 years now to suggest that bolt-on cams are and should be the bottom line for 12 valves and any other engine that is used for competitve reasons. The problem was rare at the time. But I had been lucky enough to watch a gear creep forward in early 2001 during testing of cam profiles, so I knew it was a problem, rather than a myth.

There is so much more to this, I could literally write a book......

 

So, maybe Scheid's method of preventing the problem from happening is putting this locking plate on the gear to prevent it walking? AFAIK, it is a press-on, but it's got this plate that goes in front of the gear, held by a screw in the end of the camshaft. Guess I could ask Scheid directly.

 

How long is the capscrew?

Does it look like this?:

http://www.f1diesel.com/helixspecs.html

 

The retainer looks familiar, but the bolt is not that long, as I recall.

 

If you have the right fit (interference fit) on the gear to camshaft I can't see why you would have a problem. The problem is that when you pull or press the gear on/off the gear you’re doing some minor damage the hub of the gear. If you measure the hub to check the fit you should have no problems. I used dry ice on the cam and the gear when on with no issues. I have around 0.002 and have over 100000 miles on the install. I would lose more sleep over the bolts coming lose than the gear coming off even when using a thread lock adhesive. Put a plate locker on or tie the bolts so they don't move. These engines have a tenancy to shake and rattle everything.
Don, I'm still trying to figure out how your cam build boosts at idle on a turbo charged engine.

 

Mike,
The problem is when something with helical cut gears gets shock loaded..
Really pretty simple. Its not a guarantee that it will happen because most of the time it will never happen to BUT why take a chance?

Cummins thinks its a problem thats why they use bolt on cam gears in a number of their products....