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Here is ANOTHER cam failure thread. Howards solid flat tappet with direct lube lifters broken in with Valvoline 10-30 VR-1 and break-in additive. Has 1000 miles on it. Lifters look fairly good but the tops of about half of the lobes are pitted. Car was running fine so glad I caught it before it went flat. You make the call. Never had this failure before.
How did you catch that? In other words, what made you pull the cam and find this?
thanks
The car was running great but the RPM range was not a great match with the OD transmission. I wanted to get a wider RPM range. The TKX really gets the revs down.
I'm debating doing a full tear down to make sure the grit is all gone. The bores have a few fine lines that should not be there. I'm pretty much already have it apart so what's a few more gaskets.
I was sold on installing a new hydraulic roller set up in my 496.
There are benefits to either a solid or hydraulic roller cam.
Maybe I’ve gotten smarter, older or just don’t want to mess with a solid flat tappet system anymore.
I’m not trying to make a point or start a conversation, just stating my recent decision.
I was sold on installing a new hydraulic roller set up in my 496.
There are benefits to either a solid or hydraulic roller cam.
Maybe I’ve gotten smarter, older or just don’t want to mess with a solid flat tappet system anymore.
I’m not trying to make a point or start a conversation, just stating my recent decision.
No you are right on point. I put this bigger FT cam in knowing it was a risk. Super glad I did catch it before it got away from me.
I already have the smaller hydraulic flat tappet cam and lifters here. The real failure mode in this case was inadequate lubrication combined with high spring pressures. The new replacement cam is much milder and uses lighter valve springs. New cam runs the equivalent single "brown stripe Z/28" spring so you know it will be tame.
If I wanted a max effort engine, I would look at a roller. This is a 6000 RPM redline, wide power band, hot street application that should be able to run a hydraulic flat tappet and get down the road with authority. I just don't need any more than that on this build.
You mentioned the springs. They seem pretty stiff.
How aggressive was the cam? Did it have fast ramps / quick lifter acceleration?
400#/inch spring rate. Cam was .505"/.520", 275/281. Add in the 1.6 ratio rockers and its pretty close to the edge. 240/246 at .050". I was trying to keep the spring pressure over the nose under 350# but this setup just got too stiff. BTW - I just found 1 bad Comp Magnum rocker arm pivot too.
Limit is 350# according to Comp. This one has failed.
It ran really great when it was "on cam", but not so perfect at 1700 RPM. It was borderline acceptable. 112 LSA helped but it was not enough.
I just needed to pick a smaller, less agressive cam. Just a case of too much.
Last edited by stingr69; May 11, 2023 at 05:48 PM.
Cam Failure
It was borderline acceptable. 112 LSA helped but it was not enough.