Camshaft Replacement

[Matt400]

I might tackle my cam replacement this weekend and was just reading through the shop manual when I noticed no mention of swapping the cam gear.

They say to inspect it. . duh, but if there are any cracks that it gets replaced as an assembly with the cam.



My replacement cam has no gear and its a press fit so I was wondering if anyone has done this recommends heating the gear or if thats not needed to press it off the old cam.

I just get nervous applying allot of pressure to a rotating piece, tweak it just a smidgen and its never right.

 

[SRadke]

The gear is cast iron so a "tweek" shouldn't be an issue, it'll probably break before it bends plastically. As I understand it the gear should press off nicely but it is suggested that you put it in an over at ~325° before pressing it on the new cam. Don't go much hotter than that or you risk damaging the heat treatment of the gear. I saw a picture of one with the center broke out of it after a guy heated it with a torch.



-Scott

 

[HeavyHauler]

I used a large gear puller to get my gear off the stock cam and then I baked it in the oven before I tried to put it on the new cam. Most people say 30-40 minutes at 350* or so but I think I ended up doing mine at 450* for only 15 minutes or so. All is good. It doesn't take much - we're talking thousandths of an inch here.



Make sure you have the new cam in a vise with the keyway in ready for the heated gear. I like to angle the keyway a little so that the gear goes on easier. It will fully seat when you get the gear on. You don't have much time once you take the gear out of the oven. Have a block of wood and a really big hammer handy too. You might have to use some force.



You can also just use a very large shop press to put the new gear on. Just use plenty of grease.

 

[jwilliams3]

We used a press for the install of the cam gear.

Just a little oil to make its transition easier. Thinner the oil the better as tolerances are tight.

Did not heat either.

 

[KLockliear]

A press is the best way. Off, just press the cam out. On, heat the gear for about 30 mins at 325, as said above, then quick to the press and go for it.

 

[Matt400]

I hate it when poop goes wrong

I got problems now... :{

First off, thanks everyone for the replys. The gear pressed off and back on with no trouble.



When I started the motor I thought I heard a knock sound, kinda intermittent and I was thinking... whats that?? Not real loud but enough to get my attention then it went away then I got a camshaft fault code.



Now I am thinking maybe something contacted the sensor, come to think of it I never even noticed where it was when I had the cam out. I found it on the back side of the timing cover below the CP3 and pulled it out for a look and didn't see any marks on it.



Any ideas what I did wrong?

Does the cam sensor look at the cam gear or the pump gear?

Maybe the noise and the fault code are not related, seems quiet now so maybe just valve train settling in.

I set the Intake at . 008" and the exhaust at . 017"



I had done a tone ring mod prior to this for about 3 degrees and don't see how that would effect anything. PDR claims the cam corrects retarded cam timing.

The old cam looked flush with the gear so thats how far I pressed the gear onto the new cam even though there was a tad more room to go. Pressing it further would move the gear closer to the sensor if its too far away dunno.

 

[Matt400]

Just another thought. . wouldn't there have to be a magnet on the back of the cam gear for the sensor to work?

Maybe the noise I heard was the magnet coming off. I just don't see what I could have done cuz I was real careful with the gear in pressing it.

 

[KLockliear]

I don't remember if the 3G tone rings are the same as the 2G's, but they are a slotted disk bolted to the rear of the gear. The cam pos sensor reads the windows to determine where the cam is.



The gear should have been pressed down as far as it would go, until the back of the gear hit the flat at the front of the cam.

 

[Matt400]

The gear should have been pressed down as far as it would go, until the back of the gear hit the flat at the front of the cam.

I thought about doing that but then saw on the old cam the mark of where the gear had originally been pressed to was and it was just flush.



If the magnet on the cam gear failed it seems I wouldn't get an engine start.

Tomorrow I will see if I can locate that magnet with a mirror through the sensor hole before redoing the entire job.

 

[jwilliams3]

Yeah, what Kieth says.

Its hard to get it wrong.

 

[rbattelle]

If the magnet on the cam gear failed it seems I wouldn't get an engine start.

I feel for you Matt... there's nothing worse than that feeling of taking a perfectly working machine, modifying it, and then discovering you might have screwed something up. I hate that.



I was under the impression that the ECM could use either the crank sensor or the cam sensor if one or the other failed? That would explain your ability to start it despite a nonfunctional sensor.



-Ryan

 

[Matt400]

nothing worse than that feeling of taking a perfectly working machine, modifying it, and then discovering you might have screwed something up.

Now I feel better! :-laf :-laf

Actually its just a small hitch in the job that went wrong... probably only means I gotta do it all over again, I will get some extra practice



After sleeping on it I have to agree that the cam gear should have been pressed further back because this would hold back lash to a minimum as the thrust plate is sandwiched between the gear and cam, you have to put the thrust plate on and then press the gear on over it.

In looking at the 3 wire sensor I see it may work like the crank sensor and not require a magnet.



The noise may have been the cam movement and the gear may just be too far from the sensor. I will just pull it back out now



On another note. . shouldn't there be a sizable difference in the cam lobe height vs the stocker? I put the 2 side by side and was confused at what I saw expecting to see a big difference. Today when I tear it down I will measure it again with the calipers, the PDR cam appeared to have less lift.

I was getting late so I put it in anyway thinking maybe the duration makes up for things dunno. I hope I have not detuned my 325 motor!

 

[HeavyHauler]

Should have gone with the F1 cam. The extra lift was very noticable when I sat my Helix 2 next to the stocker. It seems to me that you really haven't done much unless the cam has enough lift to require a valve spring swap. But I might be missing something there.



I hope you get it worked out. I'm sure you'll be able to notice that the cam is in there when you take it out for the first test drive.

 

[Matt400]

Should have gone with the F1 cam.

I thought about that one but not wanting to do springs I would have gone for the Helix 1 anyway.

The extra lift was very noticable when I sat my Helix 2 next to the stocker.

You didn't happen to measure the height with a pair of calipers did you?

I'm sure you'll be able to notice that the cam is in there when you take it out for the first test drive.

I hope so

 

[K Summers]

measure the heals of the lobes. the pdr cams are regrinds most likely and the heals should be closer to the shaft therefore giving you more lift.

 

[SRadke]

I wouldn't be too concerned about lift. It can be decieving with variations in shaft diameter etc taken into account. The only real good way to measure it is from the bearing surface down to the heel and the same on the opposite side from the bearing surface to the top of the lobe then subtract.



Afraid I can't help you on the noise without a better description of it. I had a realt loud knock on mine after I put the head studs in but apparetly that'll happen if you don't get that #6 exhaust pushrod back under the rocker :-laf

 

[Matt400]

the pdr cams are regrinds

I confirmed with Mark at PDR before buying it, that it is new. I know they have offered regrinds for older Cummins but the 3rd gens are new.

I questioned this when I got mine because it had a Cummins part number stamped on it, this was the reply-

Hi Matt,



No, it is a new blank. When I say new blanks, I mean new blanks.

They are not Cummins cams. We can't get our spec's out of a Cummins cam, so we had cams cast to our spec's, not Cummins spec's. It's just the same company that casts them for Cummins. They cast for other companies too.

That's why I sent you some pic's to show you that they start with a rough casting and goes through the process to get to our spec's.

 

[Matt400]

What now..

I specifically remember taking extra care to put the crossheads in their original location and position the first time. This time around I noticed a small dot on one end of the crossheads so I took a closer look at it and see that these crossheads under the rockers have a long slot on one end so they must go a certain way but mine are all different.



Shop manual doesn't mention this, anyone know which way they are intended to go?

 

[jwilliams3]

Yeah I know which way:

The answer is they can go either way.

 

[Jeff_K]

I think this is why I will get someone to install my cam for me :-laf