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Old 03-13-2010, 10:26 PM
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Roller Cam ate the Distributor gear

What are the odds an engine survives after the camshaft eats a distributor gear?

I just built a new 406 SBC, and after driving about 20 miles, I found out that I had 55 degrees of total timing while investigating unusual spark knock. I figured there was a problem with the distributor, so I just pulled it and found some of the teeth worn badly. Lookng at the teeth, it looks like one side is worn more than the other, which tells me that the problem is the cam. I may have damaged it during pre-oiling as it was a real pain keeping the old distributor shaft on the oil pump drive rod.

Anyway, I'm curious what people think about my logic here. I think that the metal created by the teeth would have washed into the oil pan, then through the pump and through the filter. The good news is that I have an oil filter magnet, so hopefully it caught most of it. I'm going to pull the engine and inspect the bearings, but I don't know if I need to tear it down completely and have the block cleaned again.

Thoughts?

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Old 03-13-2010, 10:36 PM
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I can only tell you what I'd do and that's tear it down completely and go through it like it was a brand new build, rifle brushes in the oil galleys and the whole nine yards.

But then you have to understand that I simply have no luck at all.....concerning ANYTHING. I refuse to gamble at all. I ALWAYS LOSE.
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Old 03-13-2010, 11:19 PM
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I'm a little bit lucky but don't gamble either, so like Tech said I would definately tear it down and start all over again. I take it you didn't install the special bronze gear on your dist. for roller cam use??
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Old 03-13-2010, 11:46 PM
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You need a bronze gear on the distrib, don't put another iron gear in there. Roller cams are specially heat treated and are much harder than a typical cast steel camshaft, totally different materials of construction.

Pull the pan, intake, cam cover, and valve covers. Flush the engine from the top with gasoline, diesel fuel, or whatever solvent you feel comfortable with to get stuck particulate off. In 90% of most cases the filings went straight to the pan bottom and sat there, might be a good idea to pull the oil pump off to check it for scoring...with any luck it will be fine (usually is) and you can re-fit everything and pretend it didn't happen.

The condition of the pump gears/rotor will tell you if anything went through the pump, if its all scored up it might be a good idea to check the bearings on the crank/rods. In 99% of most cases the filter caught everything and you will be fine. Make sure there isn't any stuck in the pump screen also, the particles will jam in there and replacement is usually easier than picking them out.

Before you button it back up make sure you get in the bottom of the motor from below with a bright light and look for stuff stuck to the sump sides, it tends to stick on the sides around the cam gear area and you might need to brush it with plenty of solvent to get it out of the porous casting.

You don't need to pull the motor to do any of this.
Good luck!
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Old 03-14-2010, 08:08 AM
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If your filter bypass was plugged and you was using a good filter your bearings should be fine but as mentioned your pump may need to be looked over.

When ever we order a Roller cam either hyd. or solid we always have the ever wear gear installed.
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Old 03-14-2010, 08:25 AM
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IS your roller cam cast or billet? I called comp cams twice , the first time i called them they told me i needed the polymer gear. With the last digit on my cam being a 8 , ( part number ) it told me it was a cast roller cam , i called comp cams again and a different tech there told me the iron gear on my distributor was fine. Is your cam billet or cast?
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Old 03-14-2010, 09:17 AM
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Comp told me the distro gear on my cam is "mellonized" (sp?). I called MSD to see which gear they recommended and they told me the gear on my 8360 distro is also "mellonized" and will work fine with the cam. Inspected the gear after about 2,000 miles and no signs of wear.

EDIT: Wooops, forgot to include my thoughts on tear-down... do it. I think there's a good chance you have metal distributed through the motor ahead of the pump and filter.
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Old 03-14-2010, 09:43 AM
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Quote:
Originally Posted by Pre-Tuner
What are the odds an engine survives after the camshaft eats a distributor gear?

I just built a new 406 SBC, and after driving about 20 miles, I found out that I had 55 degrees of total timing while investigating unusual spark knock. I figured there was a problem with the distributor, so I just pulled it and found some of the teeth worn badly. Lookng at the teeth, it looks like one side is worn more than the other, which tells me that the problem is the cam. I may have damaged it during pre-oiling as it was a real pain keeping the old distributor shaft on the oil pump drive rod.

Anyway, I'm curious what people think about my logic here. I think that the metal created by the teeth would have washed into the oil pan, then through the pump and through the filter. The good news is that I have an oil filter magnet, so hopefully it caught most of it. I'm going to pull the engine and inspect the bearings, but I don't know if I need to tear it down completely and have the block cleaned again.

Thoughts?
Intuitively, I'd have thought the timing would have retarded from the wear, not advanced...

In any event, do yourself a favor and find out what the material of the cam GEAR is made of.

Besides steel gears, there are cams that have cast iron-type gears pressed onto a steel cam, there are (as mentioned) melonized gears that are compatible w/the gears like the inexpensive (compared to bronze or Comp's plastic) GMPP p/n 10456413. More HERE.

Using a ~$50-a-pop bronze gear on a street driven vehicle is too spendy, IMHO. Even the mega dollar Comp "plastic" gear will be cheaper in the long run and easier to maintain. Also, bronze gears need to be checked often and replaced at the first sign of bad wear, plus cause a wandering timing setting- AND load the oil w/bronze filings.

A melonized gear is even better- IF it can be safely used.

AFA what to do about the engine, I think you've gotten that answer, too.

Last edited by cobalt327; 03-14-2010 at 07:35 PM.
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Old 03-14-2010, 10:15 AM
406cu.in. of tire smokin' fun
 

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The cam is not a billet cam, so the stock gear was supposed to be fine. I'm going to drain the oil today and see what kind of filings are in it. The teeth on the gear are not completely gone, just damaged. I don't think it would have been enough to plug the filter enough for the bypass to operate.

I'm doing all of this out of a large one car garage, so I don't have a solvent tank. What do you guys do for the cleanup? During the install I used a lot of paint thinner and brake cleaner over a garbage can.
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Old 03-14-2010, 10:34 AM
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I just went thru this with a customer and have seen this many times before.

New MSD distrib. Comp flat tappet hyd cam. M55HV oil pump.= distrib gear gone in 50 miles. Crap all thru the motor. Eats the cam drive gear, cam bearings and rod bearings. Mains are full of debris also. Oil pump junk..

I assembled the short block. Also changed his bronze dist gear to proper one. Told customer not to use high volume pump. I ALWAYS use M55A pump.

The customer ALWAYS being right, let his buddies talk him into using a high volume pump.

50 miles later brings in distrib with gear gone. Plus previously mentioned damage. Wants me to warranty motor. SORRY!!!!!!!!!!!!
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Old 03-14-2010, 10:39 AM
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Quote:
Originally Posted by BOBCRMAN@aol.com
The customer ALWAYS being right, let his buddies talk him into using a high volume pump.
A VERY good point- these HV pumps do more harm than good, most of the time.

The same old "if SOME is good, MORE must be better" deal. Definitely not the case here.
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Old 03-14-2010, 06:20 PM
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Quote:
Originally Posted by cobalt327
A VERY good point- these HV pumps do more harm than good, most of the time.

The same old "if SOME is good, MORE must be better" deal. Definitely not the case here.
A tear down would be the safest thing to do BUT if you are like the most of us and don't like the idea of doing that. To much work ect. or what ever I can tell you this fore sure IF the cam has any front and back movement it WILL eat what ever you put in it. New long block did't have the shims and it eat two sets of lifters and and cams and dribs. before we found out it was supposed to have a shim on the end of the cam. You would think a new factory long block would have what it needed.Not need checking I don't remember just how thick as it turned out they had three (3) different ones. I used to make gears for a living and have never seen steel eat cast iron or the other way around, not even fiber gears in 50 miles. Miss matched gears (wrong pitch ,wrong number of teeth or such) will/is the ONLY thing that I know will eat teeth that quick or the dribs. not in properly.

OLDROD
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Old 03-14-2010, 09:02 PM
406cu.in. of tire smokin' fun
 

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There's no shims in this one. I installed a cam button though.
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Old 03-14-2010, 10:27 PM
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My final thoughts...you said this was a brand new 406, keep it that way. I know it's a lot of work (fun work for most) but having ANY amount of metal shavings floating around inside your Brand New engine is not an option. Yes you may get away with it but is worrying about it really worth it? Not in my book

...also you can use an oil drain bucket or anything big enough to set the crank in. Thinner, solvent, brake or carb cleaner will work but I would spend the money and get the block and crank hot tanked or whatever your machine shop uses. You'll need new cam bearing and such, chalk it up as experience, believe me everyone on this board has screwed up a time or two. Enjoy your new CLEAN 406.
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Old 03-15-2010, 11:54 AM
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The stock steel gears are what is recommended for the -8 cams. We have run bronze gears on the street for years with out any problems on the billet shafts. I always set the cam end play to the tight side of the tolerace and dont forget to check the distributer set depth. Alot of the older engines that have had the blocks decked and heads milled will set the distributor down in the engie further. If the distributor is set in too low it will destroy the gear immediately....steel, bronze or polymer.
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