Panther

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

Tow-N-One

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.

Vinny P

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.

Panther

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!

Vinny P

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.

Panther

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!

Panther

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

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

blue thunder

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.

Panther

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!

Vinny P

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.