20 teeth broken off of my cam gear!!
 

Lets start with the basics... I have an NA 540 that I built last year. It as 104 hours on it. I run it hard but , thats what its made for, right. I am very anal. I always maintain everything above and beyond. I am running an RM Builder solid roller cam, nothing to big, 200 lbs on the seat and 575 lbs open.
Earlier this season, I had an oil pressure issue. I posted it here, dont know of anyone remembers it. I found a small chip of metal in my check valve, for my ESP preluber. It was hanging the valve open, causing oil to flow back into the pan, when the engine was running, thereby creating a lower than normal oil pressure. I chalked that piece of metal up to.. I have no clue what the hell this is, the filter is clean, I'll watch it carefully. Then a few weeks ago, came the bombshell !! I hit the switch for my preluber, after a few seconds of priming, the pump stops with a huge clunk. I take the pump apart to find a another chip of metal in there. I clear it out and try the pump again. I lean on the switch for a longer than normal time, all worked fine for about 1 minute, then clunk, the pump stops again. This time, the chip was pretty big, looked to me like a tip of the timing gear. So, my season was over..
Today, I tore down the engine to find 20 teeth chipped off the cam gear. The crank gear is perfect. I am running a Dart Big M block. I have alway been concerned about the fact that there is no direct oiling to the cam gear in this block. I remember a post Smitty started here on just that subject. That is what made me think, the mystery chunks were cam gear pieces. The cam roller button is perfect, I had the timing chain cover backed up to the water pump with epoxy, no chance of cam walk. I ran a straight edge against the gears while they were mounted on the engine, no issues.
There is no blueing on the gears or the chain. Apparently, there is no oiling issue?? So, what the hell caused this gear to fail? Its an Isky gear set, maybe just a bad gear?
In any case, I ordered a Jesel belt drive today. At least I can see if the belt is about to take a crap on me.

Next.. take a look at the broken ARP oil pump drive.. I have never seen a failure like that. I called Teague today. I wanted a new oil pump pick up. Since I am running ther pan, I figured get it from them. I was told that they have seen several ARP drives fail. Bob had found something with the way ARP is cutting the groove. Bob had ARP cut the groove somehow differently for him. So, I ordered the drive from him.

So, after a lengthy post, any clue on what is going on here?

more pictures

You need to completly rebuild the motor. There will be metal in the bearings. Not sure what caused the timing failure but I would not do the belt. I like the rollmaster timing chains. In the cam sprocket area make sure you have the block plugs with the very small holes for oiling the timing set. Most engine builders throw them away for new plugs not realizing they have holes. Check the cam spocket to crank spoket alignment. Never seen a problem there but something is breaking the teeth. Something is off for that to happen or you just got a bad casting

I've never seen that in cam gears. But on a motorcycle, if the chain stretches too much, it will do exactly the same to the sprokets. Busts the teeth right off. Just a thought.





Darrell.

The pieces seemed too big to go through the pick up. I took the oil pump apart, there is a minor scratche or 2, nothing too bad. Hopefully, teh filter caught anything that made its way through. Tomorrow I will pull off the rod and main caps to check the bearings.

I thought of that. However, my thought was even though I know these HV pumps can pump alot of oil , arent you taking oil from somewhere else that needs it? Like the lifters?

I have run the Jesel belt drives for about 10 yrs. Sterling also uses the Jessel belt drive as do may others. I don't know what caused your gear issues, but in a BBC marine application the Jesel belt drive is a reliable system. This could be a lot worse...like the first run in 2009.

The purpose of the holes in the front plugs is to prevent air lock in the lifter oil galleys. It has nothing to do with lubricating the timing chain. Not all big blocks came with them from the factory.

As far as this particular failure goes, the timing set looks like a stock cast iron truck set, nothing special. I would go with a Cloyes True Roller set myself. They are pretty bulletproof and have been around for a long time. The belt drive would be ok also if you want to go that route, even though I would not think it was needed in this case.

I also have got to agree with the others that with that much metal floating around, it is time for a complete disassembly and a good cleaning :(

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Vinny, I have been messing with these things for many years, in race cars and boats and have never seen a timing gear break !! but from what I see I would change the oil pump for sure...not matter how it looks...looks to me something was trying to lock up in that area...how does the dist/cam gears look ?..yes I do remeber your other post...good luck..Rob

I understand why it was done, but it definatly adds oil to the backside of the timing set I like that with a timing set rhat uses a bearing

the 2 gen IV's I pulled out of my gibson(92) had the front oil galley plugs drilled from the factory, engines never been apart, and no bearing under the gears...Rob

Vinny how much streach in the chain? It shouldnt have much. Maybe pick it up holding it at opposite ends and see how much it sags in the middle. I can do the same with mine and see if it relates. But mine is .400" raised cam. Just a thought.
Dick

Sorry Dick, but the parts are already on their way back to Bob Madera. I can say that the chain had very little play in it. I checked it by pulling it tight by twisting the crank a bit, then wiggling the slack side. It seemed fine to me.

The good news.. I pulled all my main and rod bearings. Everything looked good, so I put it all back together. The oil pump looked good, but I ordered a new Melling blueprinted pump anyway.

Vinny,
I sent you some pics..
Dick

Vinny,

Have you considered using a belt driven external wet sump pump? Not all the room needed as for a dry sump and you get the load off the timing chain/cam &dist gears and drive shaft. I made the change for those reasons and still use my wet sump pan.

.

I use Cloyes timing sets and have never had a problem. Still look like new after 150 hours turning a high volume Melling pump. I would question the quality of the timing set and look for something binding somewhere

Was the oil pump driveshaft taken out at the same time? If so, I would wonder about the oil pump. Cavitation?

After suspecting a broken timing gear and tearing down the engine, I discovered the broken oil pump drive and the damaged timing gear.

I agree, I think this gear set was a P.O.S. It almost cost me an engine. The cam spins free in the block, dont feel it was a binding issue. I am going to run a new oil pump for sure.

No I didnt, but thats an interesting thought. I have never seen anyone run one on a boat before. I dont think I would do it, but just curious, do you have a few pictures of that set-up?

Rob,

Yes, new pump is going in. Gears on distributor and cam look fine, no signs of binding.

You better get more people involved before you re-assemble. Two things failing at different ends of the engine but the cam is unaffected and in good condition? You cant chalk it up to the oil pump shaft fatigue - I just dont believe it would stress the timing chain assy enough to break. I dont see how one could make the other fail... And if it did, what the hell caused it to lose durability. I can see failure or fatige with OEM stuff but not performance level parts. Nothing adds up but I lean toward chain slap - possibly it fatigued too soon.

One thing is for sure! Thank God it didnt happen at 5000 RPM!

Oil pump is obvioulsy at the bottom. Two water pumps. Cam driven for coolant, Eickert for raw.

I would pay close attenion to the exact lenght of the oil pump shaft. When you re-assemble put the pump and shaft in, then install the distributor while the pan is still off so you can check to see how they are engaging. There should not be much upand down play. As far as the timing, get a good cloyes true roller with a torrington bearing. You should feel lucky you caught it now. It's usually the little things that cauuse the big messes. Good luck I'm sure you"ll figure it out.

Be careful with cloyes true roller chains,some have split rollers with seams (like the hex adjust). I have used them but bought a different chain for them,Smitty

Have you actually measured the chain for stretch? As the links stretch, they ride up higher on the teeth. At a certain point they will simply snap the teeth off. Could it be as simple as a bad /defective chain, that started the whole mess?




Darrell.

True. A motorcycle drive chain will cause teeth on the sprockets to bend over and break when it is worn out.

Wow, there is alot going on in there! :eek: Looks great.

The bottom line here is, I dont know what caused this failure. I am quite sure that the 2 failures are not related. The gears and chain are on their way back to Isky for his evaluation. My guess is that I simply got a bad cam gear. Hopefully, he will give me a fair evaluation, that will answer this. In any case, I ordered a Jesel belt drive, Teague ( new style ) oil drive, Melling blueprinted oil pump. I cleaned everything out, lines, galleys, cooler, filter head, etc.. I found no significant evidence of metal contamination. It seems that most of the chips of metal were too big to pass through the pick up and remained in the pan. The rest got caught up in the filter.
More to come as things progress..
Thanks for the help :ernaehrung004:

thanks for the update......good luck !

Vinny P,

I had a similar problem in one of my engines a few years ago... My "ex" builder used cast Manley timing sets like you have.. The timing gear literally broke in half in 3 places and the chain was snapped... It wiped out some valves and while we were there I had JCPERF rebuild it. It was rebuilt with the Cloyes Billet timing set which was much much better quality than the Manley race roller junk.

Also, when the engine was rebuilt the oil pump rod was also broken, just like yours.. Everything was fine, the oil pump mounting surface was milled flat and so was the pump and everything else was perfect so go figure....

Frank

Does the oil pump spin freely? Perhaps something was causing the oil pump to bind, stressing the oil pump drive shaft to the point of failure, and the timing gear teeth broke due to the extra stress on them from the oil pump. Just a thought.

No there is no binding of any kind. Who the hell knows whats happening @ 6000 rpm. But, I am leaning towards the gears and chain just being a p.o.s.

Vinny, just curious how you made out with this?

I tore down and rebuilt one of my engines that was in need of a refresh and found the exact same thing you did.... This was the other engine (not the one JC fixed a few years ago with the billet timing set) that still had the Manley Cast gearset...

Anyway, here's what I found....

1. 50% of all the teeth on the timing gear were broken off, just like yours. All the pieces were in the pan and didn't cause any damage to the engine (thank god). I had roughly 250 hrs on this engine.

2. I installed the HP Cloyes Billet cam set with the upgraded chain.

3. When installing the timing set I noticed the cam gear was 25-30 thousanths (.005 end play) further out than the crank with a straight edge. I tried a different torrington bearing to see if it would change anything and it stayed the same... My machine shop wound up machining 27 thousanths off the back of the cam gear and we determined the face of the block probably wasn't machined properly to begin with and that's why all the teeth broke off over time.

4. After having the cam gear machined and installing the timing cover I measured a HUGE amount of camshaft end-play.... Had to modify the timing cover so there was zero end-play.

So in summary. #1 the old cast gearset was crap. #2. the builder (NOT JC) didn't bother measuring to see if the gears were properly aligned and didn't bother setting end-play. So the cam was riding 30 thou out of the hole and the end-play was loose putting excessive pressure on the teeth and because it was a cast timing gear the teeth couldn't hack it!

Panther,
I feel your pain. As I said my solution was to run a Jesel belt drive. I ran it for last season with no issues. I didnt find anything to be out of alignment as you did. I blame my failure on 2 things... #1 the wrong choice of gears and chain set that Isky recommended. #2 even though it has been contested here on OSO, I believe not enough oil on the cam gear due to the design on Dart blocks.

Funny you should mention that because we drilled a small hole on the lower pad of the block just behind the cam gear so extra oil can get to the torrington bearing and timing gear! :drink:

Here are the pictures of my cam gear... looks eerily familiar, no?:drink:

PS, don't use cast junk and check your tolerances!:angry-smiley-038:
I narrowly dodged a bullet this time, others might not be so lucky.

It looks like valvetrain harmonics to me combines with cast gears. I'd change to steel gear and change my cruise rpm =/- 100rpm. Just a thought.

Not sure about Vinny's case but in mine it was clearly the misalignment, end-play combined with a cast gear in a blower engine = Recipe for disaster. Luckilly I avoided it, hopefully others will learn from it! :)

As I said, in my case there were no alignment issues. Possibly harmonics played a part, but how can you tell for sure? The bottom line is .... be careful of what gear sets you use. In my opinion, use a belt set up and forget about it forever.