W2 stroker build - cam gear interference?

Hmm...weird one I have here.

So having finished driving the oil pump shaft bushing into the block I figured I might as well get the cam in and make sure there is nothing weird about this setup, you know, gears mesh nicely, etc.

The cam is a custom ground Comp Cams hydraulic roller with a regular compatible gear drive, meaning (per the tech's email):



...and I am using the MP hardened shaft that I used with the last flat tappet cam I had. Great shape actually. OK, so far so good.

So I stuck the cam in, got the front retaining plate bolted on, slowly went ahead to turn the cam (while checking that drive teeth were meshing nicely with the oil pump drive), all was good until I hit a certain spot...then literally STOP!!! The cam was stuck...so I wiggle the darn thing around, back and fort, back and forth, toss some extra oil at it and repeated, only to find the same "interference point".

Hmm, weird I thought. I removed the cam and re-installed one of my old hydraulic flat tappet ones...spun it...super easy, no stuck spots. So at least the bushing install appears to be fine (I actually used the proper tool for it).

I tossed the roller back in there, sure enough, got to a hard spot again. But I did notice that the more turns I got on it, the easier it got. So I literally employed my daughter for the next phase, she came out to provide the honorary oil squirter duty while I hooked up my dril and started to turn the assembly on slow speed. After about 10 secs. of this I stopped, checked things out, everything seemed fine, but I could still feel a stuck spot in there. So while it got a lot smoother it was nowhere near like all the other cams I have ever installed.

So I pulled everything apart and took a few photos of the gear mesh pattern. You can see how the tight spot has let these spotty mesh markings, while the smooth part has a nearly continuous mark left.

I've never messed with anything other than hydraulic flat tappet cams, so maybe this extra tightness/interference is a normal thing for this kind of a retro-fit setup.

I'm curious, does anything here jump out at you guys? Is this a tell-tale sign of something else being wrong with the cam? Could it be bent? I don't think so because the tight spot is only across about three teeth...but who knows?

The cam and drive gear turn at a 1:1 ratio. I'd pull the drive gear , move it 180 degrees and see if the wear is in the same spot on either the cam or the gear.

There are no burrs on the new cam, right? What about on the drive gear? Because the wear marks are on the cam it would seem to me the issue is with the drive gear.

What about spinning the drive gear itself without the cam installed, is there any bind?

Send the cam back, it is not GOOD
I'm suggesting this based on using the same oil pump drive gear gear on another cam is fine

I was afraid of that...but any theories for what exactly is the problem? Is it that the gears on the cam are cut incorrectly?

I will try what Stanton suggested tonight, I suspect the pattern will just get moved to another spot though.

Either way, I am extremely reluctant to use this, so most likely this is a bit of a SOL situation as that cam was purchased years ago when I started to gather parts for the build. I will give Comp Cams a call today to see if anything can come of it.

Good catch..... will be interesting to see what the cam grinder says

Your problem is in your first three sentences of your original post. Especially when other cams are fine. It's a damn shame anymore.

Maybe you could emery paper those couple teeth to open up the clearance.

Well, I got on the phone with the Comp Cams Tech line. The person I got on the other hand was NOT at all in a rush to just throw some fancy terms at me and write-off the whole thing as "user error", point being: we had what felt like a decent and focused conversation.

After I described the issue he asked how long the cam sat on the shelft. Well, the piece was ground in May of 2014, I got it about a year later as an on-line buy, and it's been sitting on my shelf ever since. The original box, but just sitting.

His answer was: "hmm, well, it could have literally bent...by sitting on the journals just like that, for that long of a time, we have seen this type of stuff before."

Now, I don't quite know what to make of that, however for something as heavy as a crank it is always advised to store it by standing it up on it's end.

Either way, he suggested I try to check the run-out on the cam, which means I'll see if I can check against one of the journals, although I'm still thinking this is a gear teeth issue since the cam fits quite fine when installed w/o the oil-pump gear in place and it would appear there is no binding between the cam journals and the cam bearings in the block.

Anyways, more to follow...appreciate all the feedback so far!

If it rotates fine with no oil pump gear in it and doesn't rotate the same with the gear in place it is the cam gear

See what I mean ..... find a new cam company. If it was bent that bad at the one end it wouldn't even turn in the block by the time you got to the middle, if you could even get it in with out a hammer.

So it's your fault for letting it sit 7 years. I have cams from the 80's that still work fine that have sat on shelf much longer than 7 years.

Unreal.

I still say lap the couple teeth with emery until you get smooth rotation. Unfortunately.

Manufacturing mishaps happen. I have seen a flat tappet solid camshaft where the gear wasn't machined to the correct depth. When it went on the dyno, it made a mess. No idea how the engine builder didn't pick it up, but it destroyed the oil pump gear and the bush as well. Camshaft was sent back and a new one sent.
Did you buy it directly from Comp or a retailer?

Just for kicks do you have a different oil pump drive? Who knows, if both are off a hair maybe a different gear might work.

LOL. Well just flip it over and it will be straight in a couple of years .

Oh, I mean if bending under it's own weight was possible

So you guys, I think it's def the cam gear.

Here is what I've done:

1) tossed a different (stock, but used and in good shape) oil pump gear, result => same bind

2) I added a thin shim under the oil pump gear wondering if the can gear is miss-located, yeah, I realize I could not really run like that since the distributor would be off, but for the sake of the experiment it was worth trying, result => cam and oil pump drive would not mesh at all...as in, attempting to set the two up resulted in a firm stop and no further movement

3) I then removed the freshly installed shaft bushing and installed another one, wondering if maybe the bushing itself was off a tad since the top of it had an imprint from the installation tool (which I thought was weird), result => I did actually discover that this bushing was just too darn soft and the bushing installation did actually leave a missformed ring around the center, which by the looks of it would have caused one half of the bushing to be up by about 0.005" (I meassured the thickness of the top lip), I wil get a pic added later to show this

Needless to say, that wasn't it...the cam actually had an ever harder time turning...LOL, ugh???

Sssooooo...at this point in time I'm sort of ready to give up...damn, I never thought I would run into this kind of a problem, after all his is such an easy QA check at the end of the machining operation!

I suppose the only thing left is to try the emery cloth "adjustment"...

Bought it from a retailer...so I'm guessing I would be hard pressed to actually get Comp Cams to own up to the problem after so many years. But hey, worth trying, so that'll be tomorrow's goal!

Yeah, I know what you mean. I tried to be open minded about this hoping that something DIY fixable could be identified...I suppose I was living on such hopes anyways!

I will give these guys a ring tomorrow to see if they'll replace the cam for another one that doesn't have a problem. If they refuse, well, can't do much about it now, but that'll be the last Comp Cams anything I bought. That's all I can do, take my $$$ somewhere else.

In the meantime I will certainly try the emery cloth approach.

Someone didn't tighten down the cam core all the way when the gears were being cut and the core walked. I would be interested to see how far off it really is and paint the oil pump gear with marking paint. If it's tight on one side, the other side is probably pretty loose.

Make sure the bushing for the oil pump drive is seated all the way...it may look seated but you need to make sure. If it's no, it'll hold the drive up enough to make it feel rough and cause damage.

The cam core was made wrong........ simple as that.

Just send it back to comp, they’ll probably take care of it.

i have always said, if a cam or a crank will "bend" laying on their side after a while, i guess ALL metal parts do that !
ya know, cylinder heads, blocks, rear end housings, transmission cases, all your GOOD parts.

Yeah I keep jackstands under everything so it doesn't eventually droop down to the ground

Alright, so here is what I did:

1) apply the gear marking paste to the oil pump drive gear
2) install (was expecting to have to fight with this a bit and possibly messing up the patterns, but it actually wasn't a problem)
3) I then rotated the cam several times over, still fought with the "problem spot" but went through it a few times

There is a very real mark where the interference exists. The teeth leading up to it are clean, as are those past it...and maybe that is indicative that something is off? I would have expected there to be a steady mesh pattern all around.

Anyways, I did email Comp Cams (wanting to be able to share the pics), haven't heard back. I will give them a week and get on the phone. I suspect this will take time regardless.

...here is the cam side of it...

To get a pattern all the way around you would have to put pressure on the gear (turning resistance) to force a pattern to show. But see what comp says, If they swap it that would be great. Looks like the tight spot teeth have tooling chatter marks on them.