Broken camshaft driverside

vehicle is a 2010 F150 5.4 3v RGR ported heads, custom grind Bullet cams,cam limiters installed with a blower. Ive had the driverside camshaft break twice. After the first one i sent both heads back to RGR he repaired the head and supplied another driverside cam. Reinstalled everything same passenger side cam, new driver side cam everything ran good for 12,000 miles broke the driver side cam again. Both cams broke under the front cam cap where the oiling holes are drilled. Has anyone had this issue before?

Weird.
How long did it run before this happened?
I would think that the timing chain would let go before the camshaft would snap like that if something was bound up.
Any evidence of piston to valve contact? Any harsh harmonics before it went?

I’m thinking those custom ground cams have a problem with heat treatment if there is nothing wrong with the cam bore in the head.

The first broken camshaft bullet said had a defective core. Just find it odd that its happened twice on that side but the passenger side cam is fine.

RED09GT said:

Weird.
How long did it run before this happened?
I would think that the timing chain would let go before the camshaft would snap like that if something was bound up.
Any evidence of piston to valve contact? Any harsh harmonics before it went?

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The first time it may have had a couple thousand miles on it we beat on it on the dyno for about 5 hours that morning then drove from Orange Tx back to San Antonio it broke less then 10 miles from the house.

I've got a set of Bullett cams that I bought used. The driver's side cam was replaced at some point by the original owner. I may be jumping to conclusions but maybe they have had a bad run of driver's side cores?
The way it broke, looks like it was not structurally sound around the oiling holes. Is it the angle of the picture or does the center of the cam look like the top side collapsed inward a bit?

I'd see what the manufacturer has to say about it. I wouldn't think that a camshaft would be brittle in that area. The location and the intersection of the oiling holes looks odd to my untrained eye as well.

I will definitely be sending everything back to RGR for him to look it over. Just checking to see if I did something wrong with the combination like needing to lock the VCT out instead of using the limiters.

That cam journal doesnt look good in the first pic. Looks like some galling happening there.
I dont like that it has happened 2x.

He was able to repair the cam towers last time replaced the bent valves. I doubt i will get that lucky this time.

Don't like the way those oil holes are drilled offset to the internal holes, reduces cross sectional strength..
also sounds like to me, that either the spring pressures were too high or that the front springs were improperly shimmed, thus binding when the engine warms up.

The springs are PAC i will have to look at the receipt for the part number. I can check the install height the cam is a .480 .544 lift. The holes seam to be a larger diameter than the stock ones.

Repeated valve breakage concerns me. I have seen broken valves from a lean tune.

It hasnt broken any valves. The bent valves were from when the cam broke pistone to valve contact.

Oneslow50 said:

The springs are PAC i will have to look at the receipt for the part number. I can check the install height the cam is a .480 .544 lift. The holes seam to be a larger diameter than the stock ones.

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This has me worrying about potential problems with my Bullets..

If by some chance it isn't a cam core issue and your head guy has repaired everything properly with ideal cam journal diameters and alignment, that leaves me wondering what else could be going on.

Those PAC springs are probably a lot of pressure for that small lift. I'd probably ditch the limiters. I only run lockouts or full VCT personally, so is the timing/advance/duration one that could be causing PTV? What tensioners and guides are you running? What viscosity oil?

Tensioners are the older steel ones with the ratchet safety. The bottom three or four teeth have been filed down so it wont over tighten the chain but wont allow it to compress if the Tensioner fails. Tensioner side guide is aluminum mmr fixed side is the factory plastic. Oil is 5w30

Oneslow50 said:

View attachment 74511 View attachment 74512

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I'm curious about these pics!

The oil gallery holes are in the same place as the cam gear bolt holes.
So the bolt holes are at the weakest point [and bolt stretch would put tension on these 2 positions]
If the oil feed holes were clocked 90deg the cam would be a lot stronger

The comp cams are drilled the sameway except not offset. In other words they line up with the cross drilled holes not halfway through the cross drilled holes.