Broken cam pin questions????

[CNCguy]

Since there have been a few people with broken cam alignment pins I am wanting to see if we can narrow down the cause. From what I understand there are two types of cam bolts, one that is undercut behind the threads and the other is not. If those who have experienced broken cam pins could post some info perhaps we can find a common problem.

What brand cam?
What are the cam and spring specs?
What rocker arms were you using?
What brand timing chain set?
Which cam bolt?
What was the bolt torqued to?
Was there any cam bearing wear?
Was oil being supplied to a non-stock component like a turbo?
What was RPM at failure?
Any other important information?

[34blazer]

i have i question to add. is it possible to drill and match a double roller set meant for a first/second gen style cam? i like the fact that the pin also has 3 other bolts holding the cam sprocket on.

[bszopi]

Problem with most double rollers is that it will not fit behind the front cover.

[CNCguy]

The GEN-I & II cam gears cannot be made to fit the GEN-III cams. The GEN-III style uses a cam retainer plate and the early style doesn't. As Brad said, even if they could be bolted on, there is not enough room under the TC cover to clear the chain.

My reason for asking about pin failure is that we are getting ready to make some double roller sets for the GEN-IIIs and if there is an inherent flaw with the stock design, I would like to eliminate it. Really was hoping to get some feedback as well as hear from some of the full-time mechanics who have encountered broken pins.

I have only found a few threads about broken pins so it doesn't appear to be a huge problem but very expensive when it does happen. From what I've read so far, it seems as though improper torquing of the cam bolt, spun cam bearings or excessive cam bearing drag due to reduced oil flow or contaminated oil are the main reasons for pin/cam failure.

I would still like to hear from people who have encountered broken pins to gather more info as there could be many other causes. Such as some replacement TC sets could have be made differently, the undercut bolt stretches more than the straight one, oil flow to a turbo/csc is limiting the flow to the top of the engine, etc.

[34blazer]

im using the 1st TC anyway, oh well back on topic

[Joseph Upson]

Is it possible that some of the failures are due to reuse of the retaining bolt. The harmonic balancer retaining bolt according to GM is supposed to be replaced once used to install the balancer at least on the newer V6s.

[SappySE107]

I would be surprised if the harmonic damper caused it. Not running one doesn't cause them to break. I wonder why they want to replace it every time? Is it torque to yield now?

[loner666]

i think my problem was no loctite or improper torque of the bolt but ill post it anyway

What brand cam?
stock '03 3400

What are the cam and spring specs?
stock cam LS6 springs

What rocker arms were you using?
stock

What brand timing chain set?
Clevite? i think

Which cam bolt?
the one that came with the motor(not sure which one that was stated above)

What was the bolt torqued to?
I thought i torqued it to 100Ftlbs

Was there any cam bearing wear?
normal wear but nothing odd

Was oil being supplied to a non-stock component like a turbo?
no

What was RPM at failure?
less the 2500k i think at the moment it started but i had just gotten off the highway

Any other important information
dont think so

[El_Diablo]

anyone notice detonation at the time of it breaking? stock tune?

[PCGUY112887]

FYI GM calls for no locktite on the cam bolt...

It actually says to NOT use any locktite on any bolts unless it specifically says to.

[loner666]

lol..o well i did anyway..it came loose once before i dont want it to do it again and destroy my 3k top end

my tune was 90% stock..shouldnt have had any detontion at the speed/rpm i was at at the time

[geoffinbc]

What about simply enlarging the pin diameter. One could supply a pin and drill bit in kit form for the modification. The pin should also be made longer if possible and be a press in fit. Something you could tap in with a hammer.

[ForcedFirebird]

You guys are making me happier that a gen1 block is going in the Firebird.

How about modifying a roller cam and gear to accept more perimeter bolts to accent the single center bolt?

[Superdave]

You guys are making me happier that a gen1 block is going in the Firebird.

How about modifying a roller cam and gear to accept more perimeter bolts to accent the single center bolt?

Bleh.. Just weld it.