My new 347

[delexploder]

WTF! How did that happen? Did the cam seize up?

 

[Josh P]

The 302 is a non interference engine and you checked ptv clearance many pages back when the motor first went together. As for the next failure, either the block tries to divorce itself down the lifter valley or you put a window in the side of the block.

 

[Dono]

Not sure why this happened.
As for ptv clearances, I hope your right.

Remember, I checked ptv with the cam working, not with valves wide open and the piston(s) at tdc.

As the motor spun down, with the valve train at various states of misstiming to the pistons, who knows how many valves kissed pistons.

Also, these are non stock pistons, non stock valves, and a non stock cam.

 

[delexploder]

Man I'm sorry, that sucks , I asked about the cam seizing up because that's the only thing I have ever seen cause that

 

[2000StreetRod]

that's terrible!

The camshaft sprocket retaining bolt is only torqued to 43 lb-ft and it's not a tty bolt so I'm surprised it failed. Is it really necessary to pull the engine? Have you considered just replacing the bolt and doing a compression test?

What's a cam positioning dowel? I thought there was a thrust plate behind the sprocket to position the camshaft.

 

[Dono]

That cam positioning dowel is a hardened steel dowel that is pressed in to the cam. When the cam gear goes on, this dowel goes in to the gear.
Now, the dowel is not designed to take the force of the valvetrain, its supposed to be that torqued bolt.

Comp cam assures me that there is no way I'll get the rest of that dowel out without pulling the cam. This guy told me that people send in their cams to them all the time to have that dowel replaced. A machine shop can do the job also, so Comp Cam's popped a couple of dowels in an envelope and they are on their way to me. Extremely generous of them, not much is for free anymore.

So, with the cam having to come out, the motor is coming out.
I also, feel its prudent to try to understand what happened. If that bolt just came loose, I would think it wouldn't be sheared off, and just the cam dowel would be in two pieces. Maybe the cam did seize.

I'm getting so sick of this, that I wasn't even going to post it. Its down right embarrassing at this point. Its a big black cloud. When will it lift on this project??
Anyway, I decided this is a good learning experience for all of us. People don't post this stuff usually.

 

[willzilla]

Ouch, sorry to see that man :-/

 

[Turdle]

This is just plain nuts. Was that an ARP camshaft fastener?

IS there any damage to the crank keyway at all?

 

[Dono]

Crank key way is fine. I'm not sure about the cam sprocket yet. I can't get the leverage to pull it off. As I wiggle both sprockets forward, the cam sprocket binds. It's probably nothing.

It's going to be a good time to change my rack I guess. It just started leaking and the power steering fluid is a ugly brown color. I guess it will give me something to do, and less fighting with the motor out of the way.

 

[4pointslow]

broken bolt

So sorry to see this happen to you.

 

[Dono]

Tim came over and we yarded the motor out like a drown rat out of a swimming pool.

We started some time after 12:00, maybe even 1:00 and had it out by 3:30.
In fairness, I had a bunch of stuff out already just to get the timing cover off.

I'll pull the heads tomorrow as I'm back at work tonight, but curiosity had the better of me. I pulled both valve covers, and the rockers are exactly where they are supposed to be.

Maybe I'll see the cause of this tomorrow.

 

[Josh P]

Did you use locktite on the cam bolt?

 

[Dono]

The machine shop put the short block together. All I did was heads, timing cover, etc. so I can't comment on the lcktite.
I can't see this being the issue though, as the cam bolt sheared in two. Half of that bolt is still in the cam (along with half of the locating dowel). What could cause that cam bolt to shear in two? I mean, its in the centre of the cam and timing gear, so it wouldn't have had side forces tearing at it on it if it it came loose.
I did find ARP stamped on this cam bolt.

 

[boominXplorer]

Wow that sucks. The only way that could of happened is a bad quality bolt or it was over torqued and stretched.

If it's a clean break past the threads you can use a pick to spin the remainder of the threads out if there is a piece sticking up, that is unless it has loctite. Still doesn't fix the down issue

 

[Dono]

The valve train looks good. ARP bolt. I wonder if the bolt was impacted on? I've always had great success with this machine shop, but who knows what happened when you were not there and didn't do the work yourself.
I do agree that this really blows though.

I don't know what I would do without Tim continually coming over and helping me. Doing and re-doing gets pretty over whelming. One of these times this thing has to stay together.

 

[boominXplorer]

I wonder if the bolt was impacted on

This is what I would assume. Is there shiney marks at the corners of the head of the bolt? I know some good trans builders that will torque valve body bolts with a 1/4" air ratchet. I have used an impact to tighten crank pulley bolts myself which isn't the best way but I have never had one snap down the line.

 

[Turdle]

I was digging around and found this

http://forums.corral.net/forums/5-0-5-8-engine-tech/1871681-broken-cam-bolt-dowel-pin.html

Lifter rotated and wedged the camshaft lobe.

 

[vroomzoomboom]

however, this time by the looks of things the head gaskets survived!.....

 

[delexploder]

I was digging around and found this

http://forums.corral.net/forums/5-0-5-8-engine-tech/1871681-broken-cam-bolt-dowel-pin.html

Lifter rotated and wedged the camshaft lobe.

This is my suspicion as well , I've seen this a few times in person

 

[Dono]

I pulled the lower intake, and the spider/dogbones are holding the lifters perfectly.

I'll be pulling the valvetrain of each valve (one at a time), tagging and bagging looking for something binding.
Then the heads come off. I really hope that the end result of my build left me with a non-interference motor.