Monster 406 : Down but not done

[Monster]

This is what happens to an FE when a builder uses stock valves instead of replacing then with new SS valves .......

We were on our way back from Not Knotts crusing along at 70mph (2200RPM)The valve broke-jamed the piston-which cause the rocker to snap the end of the rockershaft off and breakout the side of the cylinder. All in a matter of a couple of revolutions





The good news is we're fine, the block can be repaired, I get to put my "new Edelbrock heads on, along with a number of new parts I either need to replace or have wanted to upgrade (pistons, rods, cam, carb, etc..) So maybe it'll be ready for Tour de Vin. If not you guy's will have to try to keep up with my CRX .

Mike

[MetaJacko]

End of the rocker shaft snapping!
Oh how that brings back memories

Are you sure the fault is the valve? From the pictures it looks like you are using an OEM rocker shaft Mine snapped becouse of lack oiling on the end rocker coursing it to be slightly slow on closeing and the piston to hit the valve resulting in 'snap'. (At least, I think thats what happened)

Oh well! At least you have an excuse to upgrade now

[Clois Harlan]

On my orig FE engine,my stock rocker arms snapped at the same place (end pass side). Damage was not catastrophic but it did encourage me to go with the EB Aluminium heads and Sig Erson Roller Rockers, Smith push rods, Comp Solid lifter cam and dual springs and new solid lifters. But all is well now.

Clois

[CJ428CJ]

Ugh! That's ugly. I hope you get it back on the road by Tour de Vin. What's this about a CSX? Oh wait, you said CRX. Darn, I thought maybe you had a new car you were going to debut.

Chris

[Monster]

Yes, I'm aware of the issue with the rocker shafts, in fact, until I got into trying to get things repaired after the tow, that's what I thought was the problem.


I'm pretty sure the sequence of events went valve head separated from the valve stem first, it's hard to tell from the angle of the picture but the head looks like it just broke off at the base of the stem (where the 2 are bonded). this let the stem go back up the guide but due to build-up and taper at the end of the stem where it broke, the stem stuck in the guide, on the next revolutions the rocker could not depress the stem and this caused the rocker shaft to break at the known weak point. With the head of the valve now loose in the cylinder when the piston came back up it jamed and caused the piston to deflect to the side which broke out the side wall of the cylinder.


When I put the 2 pieces together they line up perfectly straight with no deflection in the valve stem , which would not be the case if the head had contacted the piston plus when I look at the piston the only marks on top are where the valve head was stem down on the piston when it came up.

So lessons learned so far :

If you have an FE replace (at minimum) the rocker pillars with upgrade pillars that provide end support (best to replace the entire rocker assembly).

If you are having an engine built, or purchase a "rebuilt" engine using iron FE heads make sure the valves are/were replaced with stainless steel (min.)

406 FE is a very rare engine with lowest production numbers of all FE's, as the result it's $$$ to repair if you need new pistons


later,
mike

[ChrisH]

Like I said before Mike, let me know if you need another set of hands to help you get done for TDV. I'm right there in town.

[Tony Ripepi]

Yo Mikey,

I'm going to out of town for TDV.

There may be a spare Cobra or two sitting around in lieu of the CRX.

T

[Monster]

Chris- thanks for the offer, I'll keep it in mind when I get ready to re-install. The removal went very smooth, I had my brother-inlaw in town for mty niece's wedding and talked him into "helping" he's a car guy so it was fun.

Tony- Thanks for the offer gas them both and Marv can check out the shelby while I enjoy the coupe

take care,
MIke