Robert O

The only thing I can see that would have led to the catastrophic failure of the bolt would be the siezure of the gear bushing. But then the bolt shoulder shows no signs of seizure.So then it leaves one of two scenarios.Either the bolt was not torqued enough and worked its way loose and led to the breakage or it was overtorqued and pulled the threads upon install

SpitfireS

Robert O Posted on Jan 5 2011, 01:20 AM
The idler gear turns clockwise (viewed from the front) so one would expect it to tighten the bolt?
IF the bushing got seized.
IOW: driving along with a time bomb

How much play is there between the gap in the head and the idler gear assembly?
(including the front washer)
I mean.. how much can the idler gear move forwards IF the bolt loosened?
Enough to lose the support of the bushing that sits in the head?

Robert O

The spacer washer should prevent and contain the thrust of the idler gear/sprocket assy.That is until the bolt parts and allows rotational forces to cock the assy sideways,which appears to be what happened here.I'm guessing that the aluminum threads were pulled from the head stand which allowed the bolt to disengage and rotational forces then took over and snapped the bolt in two.The bolt head recess was likely chewed up upon this happening as once parted the bolt then rotated along with the assy.IMO this bolt/bushing setup is a crude one. I would expect an open type roller bearing of sorts.I'll be inspecting mine closely on next valve adjustment.Otherwise ,I'd sure like to determine the exact cause of this meltdown as an ounce of prevention is worth a pound of cure.Maybe two or three pounds.

Blucky87

My friends and I were amazed at how the bolt haf that was stuck in the head would not drill out even on a drill press. the bolt is very very hard.
We still don't understand how it could have snapped in half if it was that strong

Nickamsweet

I had this exact same issue with my engine except it snapped during operating at 3krpm...

The guy that took my engine apart said that there seemed to be some issues of oil circulation especially on the cams?? So maybe have a check?? Said one of the oil galleries had some debris in it...

Unsure if it def was for this reason or wear and tear or something??

SpitfireS

The idler gear bearing is lubed by pressurized oil.
Just like the cams.


Picture#1 - the red dot on the left is the oil source.
(now look at picture #2 first before reading on)
The long red arrow of picture #2 goes into the smal hole, along the bolt into the chamber between bolt and bushing, out through a hole in the bushing.



Picture #2, the oil is distributed to the rocker shaft (hollow) to feed the cams, vtec, etc. and to the idler gear bearing (long red arrow)
Now back to #1.



Picture #3, out through this hole.



Picture #4, into this groove.
A true journal bearing.

But why that bolt snapped...

s02k

Not sure why it broke.. just one of those things I guess, Got another head on the way and brand new bolt seal and bushing so with the info you just gave me about the oil passage's ill make sure that I spray it with some carb cleaner and compressed air to clean it up before I install it.. Thanks Sir

Also was thinking before I install this head to swap in some ap2 retainers and rockers but I forgot what all I haft to order?

Nickamsweet

might be worth taking apart the old head to see what happened?? In my case it was for exhaust piston 4 IIRC..

funkemonke

so, you got your new head? when you doing it?

s02k

I bought one but hasent came in yet