Careful with that camshaft

[XfireZ51]

Busy w “refurbing” the motor this winter. Pete has it and in process of swapping over components to a different short block. During disassembly of the valvetrain Pete loosened the timing gear bolt on the snout, a pretty typical procedure for refurb.
The camshaft snapped into 2 pieces as he applied the necessary torque to loosen the bolt. (See attached). In all the years Pete has been doing this, nothing like it has ever happened. So I decided to ask Marc, given his vast experience, whether he has an experience with a cam breaking that way. Marc said he had never seen that before, but also offered a tip on this procedure. I asked if I could post for the rest of the community and he kindly agreed.

Here is his response:

Hi Dominic,
>
> We have not had that happen. Long ago I would hold the back end of the cam and loosen the cam sprocket bolt. I guess I got lucky and never broke anything. I became concerned about the stress along the cam. For the past ten years or so we let the chain take the load. After removing the cam cover the first thing that we do is loosen the sprocket bolt without holding the cam. This way the torque does not go down the shaft of the cam.
>
> Maybe you found a cracked or weak cam the safe way rather than at 7000 rpm.
>
> Best regards.
>
> Marc

The camshaft of course was never designed to take that type of twisting, and as our components get older, they become more frail just like we do. 😉🤣

So just thought I’d pass along some words of wisdom.

[Dynomite]

Thank you Dominic and Marc for the Information :thumbsup:

In "Solutions" under ZR1 Engine/CAMSHAFT :cheers:

Seems to me that can also be a pretty good load on the chain (maybe not) :dontknow:

[Jagdpanzer]

I hold the end of the cam shaft firmly with a box end wrench and loosen the sprocket retainer bolt with a 1/2” pneumatic impact. The impact hammer blows do a good job of breaking the bolt free of the Loctite without putting an excessive twisting force on the camshaft.


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[Jagdpanzer]

Dom,
What does the fracture area look like? Surprised it broke that far down from the drive end.


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[XfireZ51]

Dom,
What does the fracture area look like? Surprised it broke that far down from the drive end.


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Phil,

I can try to take more detailed pics of the fracture if that would help. It went on a diagonal. Al Dashto took a look and thinks there may have been an infiltration of oil into the casting. We just don’t know. But perhaps someone like yourself can help in determining whether this could be a singular event or perhaps a leading indicator.

[LGAFF]

Super Brittle.... I had one snap off on the opposite end..... also seen several with snout failures

[grahambehan]

I would also be very interested in looking at the fracture surface. Also were the valve springs compressed on that cylinder, thereby imparting a bending moment also.
Furthermore were the slave caps on at the time, what type of tool was used to hold the rear of the cam.

Graham

[XfireZ51]

I would also be very interested in looking at the fracture surface. Also were the valve springs compressed on that cylinder, thereby imparting a bending moment also.
Furthermore were the slave caps on at the time, what type of tool was used to hold the rear of the cam.

Graham

Graham,

The cam was out of the cylinder head I believe. I’ll see if Pete can provide further detail.

[Ccmano]

Dom,
Is that camshaft original, reground or aftermarket?
H
:cheers:

[grahambehan]

Dom,
Is that camshaft original, reground or aftermarket?
H
:cheers:

Looking at the picture, I would say that is not a stock cam.

Graham

[XfireZ51]

Hans,

The cam is a regrind. Its an intake cam that was installed when we first installed a set of ported heads, so its been ~ 7 years. I later added a set of exhaust cams ~ 4 yrs ago. So I have a paper trail of the incremental power each upgrade can result in.

[Pete]

I use custom made aluminum temporary cam caps i install these on all the cam journals then use a breaker bar and box wrench to break cam bolt loose.
I have taken off 100's of LT5 cam bolts this way for 20 years with no issues.

I do not have any back history on this cam.
I have been buying and accumulating cams the past 20 years so at this time i can only speculate.
Maybe small crack that got worse with time or i'm just very strong.:)

What ever it was i have never seen this before.

Pete

PS
Regrind has nothing to do with this break i have 3 dozen regrinds out there running for years with no issues some with really hard racing time on them especially the ones in Al's,Bobs and my ZR-1's for the past 15+ years and these are the fastest N/A pump gas ZR-1's out there.

[XfireZ51]

Yep, there’s really no telling what the critical flaw was for this particular cam. I’m relieved however that this happened on Pete’s bench and not while the motor was operating.
Any chance these were magnafluxed prior to install at Stillwater?

[Karl]

I use custom made aluminum temporary cam caps i install these on all the cam journals then use a breaker bar and box wrench to break cam bolt loose.
I have taken off 100's of LT5 cam bolts this way for 20 years with no issues.

I do not have any back history on this cam.
I have been buying and accumulating cams the past 20 years so at this time i can only speculate.
Maybe small crack that got worse with time or i'm just very strong.:)



Pete I am way stronger than you...lol....odds are it was a bad cam. How it became bad I don't know.... You or Marc can change the cams in my Z anytime.

Holding it from the back or not won't make a difference if a billet steel camshaft is going to break or not.

[grahambehan]

Cam is chill cast iron, not steel.
No mag check at Mercury Dom.
Graham

[XfireZ51]

Cam is chill cast iron, not steel.
No mag check at Mercury Dom.
Graham

Thx Graham.

Karl,

The inclusion of a hex head at the back end of the cams would indicate that the factory intended it to be used for some reason,
ie. torqueing the cam gear retaining bolt.
Again, we’re dealing w components that are approaching 30 year service cycle.
Frankly, I am amazed at how members of this community, Marc, Pete, Corey et al continue to evolve the performance envelope of the LT-5. That’s also a testament to the original design of the motor.

[grahambehan]

The hex is there to facilitate moving the cams so that the timing pins can be inserted, the cam bolts were tightened with no support at the rear of the cams, just the pins. The rear hex has been used to torque the bolts by virtually everyone that has set cam timing on an LT5, tho and is a common practice with very few incidents of failure. The cam snout breaking off tho is a far more common occurence.

Graham

[XfireZ51]

Here is perhaps a better view of the break if this helps.

[Karl]

Super Brittle.... I had one snap off on the opposite end..... also seen several with snout failures

How many failed LT-5 camshafts have you come across?

[spork2367]

They are castings, they just aren't designed to sustain that kind of twisting torque load. Installing the cam gear bolt when new requires less torque than breaking one loose.

[A26B]

Quite awhile back, I purchased 31 LT5 engines the came out of a GM warehouse. Most of the engines were in some state of disassembly which included some loose cams with the sprocket still bolted to the cam. I put the cam in a vise clamping the hex end in the jaws to remove the sprocket/cam bolt. I didn't measure the twist in the camshaft, but it had to be in the 15~25deg range before I quit. Very spooky. After that, I would nest the camshaft in the cylinder head with the retainers & pin the cam with the timing pin. Works very well to remove/install the cam sprocket bolt.

[LGAFF]

How many failed LT-5 camshafts have you come across?



I bought an engine from a guy in Georgia; one of the cams had a bad snout, and then I got a bunch of cams from Dave Generous from the Callaway program and several of those had broken snouts

[WydGlydJim]

I think I was told not sure by who, probably Jerry, to use the pins to hold the camshaft, instead of the rear hex head...I suppose theory is shortening up the distance reduces twist?

[Pete]

I think I was told not sure by who, probably Jerry, to use the pins to hold the camshaft, instead of the rear hex head...I suppose theory is shortening up the distance reduces twist?

That will work for removal.
Will not work after you degree cam.
Sometimes pin hole does not align after degreeing the cam.

Pete

[richarde]

After having degreed the camshaft with the sprocket pin in place, I use the following process:
1) Ensuring that the sprocket pin is in place with the sprocket washer and the camshaft sprocket bolt nipped up to around 50ft lbs, check if the camshaft timing pin J37326 will fit through the cap into the cam.
2) If the timing pin does not align with the cam, rotate the crank very slightly until it does align. Insert the timing pin to positively hold the cam from rotating.
3) Remove the camshaft sprocket bolt, clean the threads in the cam with a solvent to remove any oil etc and fit a new camshaft sprocket bolt, applying oil to the bolt flange only plus Loctite 262 to bolt threads only. Torque to spec (factory replacement bolt 19ft lbs plus 80 - 85 degrees) or Jerrys Gaskets ARP bolt 10090566 to 80ft Lbs.
4) To be very safe, you can also use a 0.020" strip of cardboard to fit between one of the temporary camshaft retaining caps and the cam, in order to further prevent any slight movement of the cam.
5) Remove the timing pin (and 0.020" strip of cardboard if used) and re-check timing.

[wfot]

I figured I would share this that I figured out about the sprocket removal. I bought a disassembled engine and had the very same fear of holding the cam in a vise or the head an did not want to put any more stress anywhere that it did not have to be.

ironically, the cam chain is basically identical to every aftermarket ford motorsports 302/small block timing chain kit. from that ford motorsports kit I used the chain and crank gear. looped the FM/302 chain around the LT5 cam gear on one end and the FM/302 crank gear on the other end of the FM/302 chain put the whole set up into a vice and pinched the chain tight. looks like a figure 8. muscled the cam blot came right out with zero stress on the cam or the cam sprocket. Worked like a charm on all 4 cams. I ended up putting zip ties to help hold the chain around the crank gear.
it was a surprise to me that the chains were pitch but a good surprise

John

[JThomas]

I use custom made aluminum temporary cam caps i install these on all the cam journals then use a breaker bar and box wrench to break cam bolt loose.
I have taken off 100's of LT5 cam bolts this way for 20 years with no issues.

I do not have any back history on this cam.
I have been buying and accumulating cams the past 20 years so at this time i can only speculate.
Maybe small crack that got worse with time or i'm just very strong.:)

What ever it was i have never seen this before.

Pete

PS
Regrind has nothing to do with this break i have 3 dozen regrinds out there running for years with no issues some with really hard racing time on them especially the ones in Al's,Bobs and my ZR-1's for the past 15+ years and these are the fastest N/A pump gas ZR-1's out there.

I'm going to go with you're "Very Strong"! :thumbsup:

[Pete]

I'm going to go with you're "Very Strong"! :thumbsup:

Ok we'll leave it at that 🤣🤣

Pete