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Bronze Distributor Gear Shot in 4500 miles?

J

jonward786

Member
Hey guys

So driving home last night the car died on my street. Not like ran out of gas sputter and die, but die like no spark. After checking spark from coil to diz it was good. Checked spark from diz to plug, no spark. Pulled cap off diz, cranked engine, rotor did not turn. Pulled the diz out and the bronze gear on the diz was completely mangled. Teeth looked absolutely terrible.

My question is: why would it do this? The came is COMP Cams 35-421-8. I was told i had to use a bronze gear, but after 4500 miles the cam just ate right through it?

Any thoughts on what causes this?

-Jon
 
Hmm after reading around, it seems that this is a typical lifespan of a bronze gear. They are not intended for street daily driven use apparently. They are meant for racers and meant to be "sacrificial" so the cam gear doesn't ever get damaged. And i read that a symptom that the gear is starting to wear is the timing will start to retard. Which is exactly what happened. Engine started idling rough, so i check the timing it had fallen from 10 to down around 3. Put it back up at 11ish. I guess ill get a composite gear cause i really dont feel like replacing this thing every 5k haha. Lesson learned!
 
Don't ya just love talking to yourself......

Glad you found the problem and solution.
 
Dunno how many folks follow Jeff Ford on Youtube and his "Auto Resto Mod" videos. The current episode just posted this week covered him installing a Pertronix distributor in his project '67. One of the specific items that was addressed, ironically enough, was a bronze dist. gear he had installed. Seems Jeff spent the money to buy one and have it pressed on. After talking with his engine builder he was directed to remove it and install the original steel gear. Seems Jeff followed a bunch of folks' advice on the 'net....mistakenly. I'd have to watch it again to see which cam he had installed, but you might want to check it out.
 
Yeah, I've heard of that problem with the bronze gears, Jon. A steel gear should fix the problem. Make sure you change the oil and filter, obviously.

Btw, where is 'home'? I moved up to elk grove with the gf recently.
 
The only reason i put a bronze gear on there in the first place was because the engine builder was adamant i do so. The parts guy i bought it from also was like "oh yeah, you definitely need a bronze gear with a roller cam". Now after this happened i go on comp cams website and it says my cam will work just fine with the stock steel gear that comes on most distributors.

I guess the lesson here is, just because the guy has been building engines for 30 years doesn't mean he knows what he's talking about. Im just glad the engine died on my street and not in the middle of nowhere. Time for another oil change.

Tad, im an hour north of you in yuba city. living at home for now and talking to some local friends about jobs. So youre done with slo for good then?
 
Wait, do you have a flat tapper cam, or a roller conversion? The roller cam will require a steel gear, a flat tapper cam will require a cast iron gear.

We moved to elk grove so my gf (fiance, now) could go to UC Davis, and we're looking at buying the house we moved into. When she graduates, I'll probably be going to Sac State to finish things up. So yeah, no more SLO, at least not in the forseeable future. It's just too expensive to live there.
 
The rebuild used all roller components, cam, rockers, lifters. I think the confusion can be attributed to the fact that comp cams makes some of their roller cams out of billet steel cores which will eat any gear for lunch, so thats why they say to use bronze (or composite) distributor gears with those ones. Having bronze shavings in your oil is more desirable than steel or iron shavings haha. Somehow people started assuming all roller cams were billet steel i guess.

(Your post got cut off Tad)
 
Fixed. Stupid ipad.

All roller cams ARE billet steel. Flat tappet cams are cast iron. They recommend bronze gears because bronze is softer than steel but harder than cast iron, so in theory it could work on either type of camshaft. Obviously they don't work so well on the steel roller cams.
 
You mean bronze is softer than cast iron? The distributor gear should always be a softer metal than the cam gear.

My roller cam is not billet steel. The 'Xtreme Energy' roller cam line made by comp cams are "austempered ductile iron" which is similar to cast iron but harder which is why i can use a stock steel gear. So there is no reason i need to go through the hassle of using bronze i guess. The steel will hold up against the ADI much longer.

But yes, most of their roller cams are billet steel, which would need the bronze gear because its gonna eat through anything regardless. Austempered ductile iron is relatively new in cam production (maybe comp cams is the only company using it for some of their cams) which is why many people still think all rollers are billet steel.
 
That's weird, but really cool. Never heard of it, but I get it. Basically heat treated iron for reduced cost with better physical properties than regular cast iron.
 
That is the same thing I got when I bought a really extreme comp cam roller cam.

Well, I usually do things backwards like reading about the part AFTER I've already bought it.

So, I switched to a steel cam gear and the bronze gear is an ornament on my counter.

They really need to add this as a "warning", or foot note that this type of cam gear is not intended for life on the street.
 
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