Distributor Gear Chewed Up? - Team Camaro Tech
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post #1 of 21 (permalink) Old Jul 29th, 02, 07:13 PM Thread Starter
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Okay motor head buddies, I need some more help. I have a brand new crate ZZ4 short block, TFS 23 degree heads, Comp Cams Hyd Roller, MSD billet distributor/Digital 6 ignition, and all of the associated goodies. I went for another break-in ride yesterday (I only have about 200 or so miles on the whole combo), and the car died. Just lost power, no noises or anything.

The car would not start, but turned over without issue for MANY tries. After diagnosing the problem, I determined that there was no spark. Isolated it to the distributor, the rotor was not turning. Pulled the distributor, and the cam gear was totally chewed up, rounded off big time in one section. I don't get it.

I have had more problems with this car, this is the second motor. I am not a pro, but have done numerous motors in the past and NEVER had a problem. I am using great parts, and checking everything that I can, but still have these freak issues. What the heck could cause the cam gear to let go? Is this another "suspect" issue with the cam? I had no issues with the motor break in, it always had plenty of oil pressure, I did not beat on it at all (was extra careful), used plenty of assembly lube on the gears, changed the oil, everything I was supposed to do. Now I am looking, yet again, at a motor that is contaminated with metal, and do not know why it happened.

Could it be the oil pump siezed? to be honest, I did not notice the oil pressure after I tried cranking it up, but I think I would have noticed that? Any other ideas? Am I just not destined to have a killer 69????

Any ideas appreciated.

69 SS, ZZ430 Look-alike, Tremec TKO, Hotchkis Suspension
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post #2 of 21 (permalink) Old Jul 30th, 02, 07:49 AM
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Try using a flat blade screwdriver to engage the oil pump shaft in the dirtributor hole and turn clockwise. Should be able to tell if it is stuck.
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post #3 of 21 (permalink) Old Jul 30th, 02, 08:06 AM
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If the oil pump is not seized, there is the possiblity that the distributor gear is not compatible with the material of the camshaft.
I read an article describing what went with what. The problem is the billet steel (if that includes your cam) is very hard and wears away the dist. gear. In my case, with a crane cam (non billet)and the factory dist gear, sufficient material was worn away from the dist. gear to throw the timing off so that the engine would never start. Just a suggestion.
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post #4 of 21 (permalink) Old Jul 30th, 02, 08:33 AM
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A comp cams hydraulic roller cam requires a bronze distributor gear to be used, or else you end up with just what happened, the ditributor gear gets eaten by the harder cam distibutor drive gear.

ALL aftermarket (Comp, Crane, Isky, whoever) roller cams are made from billet steel slugs. Some have softer iron distibutor drive gears installed, but you would know that if your cam had it because the gears are darker than the rest of the cam.

Only GM performance cams (ZZ series crate motor rollers are not GM cams, although they carry GM part numbers) do not require bronze gears.

ZZ cams made by TPIS have cast iron gears, and do not require bronze distributor gears. GM ZZ cams say you are supposed to run a bronze gear in them in all the literature for the engines.

Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine
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post #5 of 21 (permalink) Old Jul 30th, 02, 11:42 AM Thread Starter
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I thought about the cam gear also, but read somewhere that this was not an issue with the newer Extreme Energy cams (it isn't a billet cam). To confirm, I called the Comp Cams tech line, and they also said that it was not necessary, that the stock style cast gear is fine.

I have not had a chance to look further into it, hopefully will tonight. I can't wait to see how the gear on the cam itself is going to look, I have this wonderful feeling that I will need to replace it. Joy.


69 SS, ZZ430 Look-alike, Tremec TKO, Hotchkis Suspension
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post #6 of 21 (permalink) Old Jul 30th, 02, 12:14 PM
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Mean 69,
Sorry to hear that.

As you know, GM says only the melonized dist gear should be used with the ZZ4 roller cam....but you're using a Comp Cams roller? It isn't billet? Or is it a billet cam with an iron gear? I'm confused.

If the oil pump locked up, it would shear the roll pin....everyone I've ever seen anyway.

Don~ ZZ430DropTop
70 RS/Z28
67 RS/SS Convertible, 70 RS/Z28

[This message has been edited by ZZ430DropTop67RS (edited 07-30-2002).]
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post #7 of 21 (permalink) Old Jul 30th, 02, 12:23 PM
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Sorry to hear about this, I know its expensive but hang in there. How much end play is in the cam. Comp recommends .004 to .010. Are you using the thrust plate at the front of the motor? Are you using a thrust button on this cam. Just some thoughts.

Black 69 camaro
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post #8 of 21 (permalink) Old Jul 30th, 02, 01:31 PM Thread Starter
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To be honest, I did not check the end play on the cam. I am using the stock thrust plate that came with the block. I am not using a thrust plate.

ZZ430: Good point on the oil pump, the pin holding the gear on the distributor driveshaft is intact, doesn't seem to be upset at all. One more thing, I was pretty happy with the performance prior to the failure, It really pulled alot harder than I thought it would for such an easy, mild combo.

As far as the billet cam, no, the cam is not billet, at least it sure doesn't look like it. It looks just like any ordinary hydraulic cam, which I thought was interesting (except for the fact that the lobes are a heck of alot rounder). The cam gear seems to be part o the forging, it does not look like it is pressed on after the fact. Beats me.

So, anyone want to join me for a cam swap/oil pan removal???? Actually, what I need right now is someone to help me push it uphill into the garage!


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post #9 of 21 (permalink) Old Jul 31st, 02, 04:48 AM Thread Starter
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Update: Oil pump turns fine, seems smooth and I could not feel any binding. With a flashlight, I looked down the distributor hole, and could see some chips off of the distributor drive gear on the Comp Extreme hyd roller cam. Second Comp cam I have had let go in less than six months. I think I am going to go with a Crane this time around....

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post #10 of 21 (permalink) Old Aug 3rd, 02, 02:38 PM
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Again - ALL roller cams are STEEL BILLETS, and you CAN'T use a conventional distributor drive gear with ANY roller cam (unless you pay the extra $$ for the applied cast-iron drive gear on the cam). If you buy another roller cam and use the same type of distributor drive gear you've been using, you'll have the same failure again.

'69 Z28 Fathom Green
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post #11 of 21 (permalink) Old Aug 3rd, 02, 04:54 PM
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Hmmm.... not to be contrary but Comp Cams says different on the matter of the gears.

I specifically addressed this distributor gear question with their tech guys - several different times to be sure. They were adamant that their hydraulic roller cams do not need a bronze gear. No extra charge - they just come this way now (this was Spring 2001) And for that matter - no ceramic tip on the mechanical fuel pump rod. I've been running mine with a standard MSD gear and standard Chevy fuel pump rod since day one and all is well.

In fact, I pulled the distributor this afternoon to swap the vacuum can and checked the gear out. It looks fine and has the normal wear pattern.

I don't know what CC is doing different with their roller cams but it's working fine for me.

'69 400SB, Richmond 5-speed
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post #12 of 21 (permalink) Old Aug 3rd, 02, 07:57 PM
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JohnZ- i have a gm HOT hydraulic roller cam (made by Crane, i believe?), and am using the stock gear on the crusty old HEI i had lying around.. so it must be a time bomb waiting to go off, right? i would believe that- if i hadn't been running it like that for over 2 years and probably 30,000 miles. it has seen lots of idle time, lots of 3500 rpm sustained for an hour and more at a shot on the interstate, and a few 7200 rpm blasts just for fun. it shoulda let go by now... so not ALL roller cams require the bronze gear, just some aftermarket ones.

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post #13 of 21 (permalink) Old Aug 3rd, 02, 09:21 PM
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The CC street hydraulic rollers I've used are cast steel, not a billet. The Crane hyd. roller in my own car is a billet with a pressed on iron gear and rear journal.

You'll need to run whatever the cam grinder says to run with their stuff.


[This message has been edited by Tom Mobley (edited 08-03-2002).]
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post #14 of 21 (permalink) Old Aug 4th, 02, 01:53 PM Thread Starter
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I second Tom's comment on the cam material. The one I pulled out (Comp Cams Extreme Hyd Roller) is NOT billet, it is actually cast iron. I have no idea how they get this to work with roller lifters, I thought that the pressure necessary to make a roller work required hefty valve springs, etc. It was my understanding that the surface rpessure on a roller necesitated a billet steel cam. I'll take a picture if anyone needs to see this, but trust me, it is not a billet cam.

The Crane I just installed, by the way, IS billet, with a cast iron cam gear pressed on. The cast iron part actually comprises the gear and the last bearing journal. By comparison, it looks gorgeous next to the Comp, not like that matters though.

Some more info regarding the two. The Comp I used is a "423" grind, which has .502/.510 and 224/230 @ .050", 110 lobe center. The Crane I selected is very similar, .510/.528, 222/230 duration, but has a 112 centerline. I honestly expected to not feel a difference, but could immendiately upon startup. The car now idles smoother, and pulls about 1-2 more inches of vacuum at idle. Oil pressure is good, I did my best at flushing out the block/pan with kerosene (a trick I learned from one of my friends here) and everything so far seems fine. I have not driven it yet, will tonight, but I thought I'd share the update.

I really did not expect the change in idle characteristics, I have to attribute to the increased lobe center. Anyone else ever see this before?

It was a depressing exercise, roller cams aren't cheap and I hate scraping gasket material, but I think things are going to be fine. Can't keep a good Chevy down!


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post #15 of 21 (permalink) Old Aug 4th, 02, 07:28 PM
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