Lifter Bore Failure

[andrewlandon67]

Well, after my 1914 ate yet another set of chromoly pushrods last month, I decided to have a friend of mine help me try and check valve geometry to see if that was the problem. While we were getting things set up on the #4 intake (the most recent failure,) with the adjustable pushrod, we heard a fairly substantial knock as the motor was being turned over. I had my buddy keep turning it while looking down the pushrod tube, and lo and behold, the lifter was snapping almost 1/2 an inch down while under spring pressure! We immediately short-blocked the motor, and found that the #4 intake lifter bore was missing a huge chunk of metal on the top side of the lifter bore, and was ovaled out along the outer edge, while the #1 intake bore was not far behind. Aside from my apparent lack of skill in diagnosing catastrophic valvetrain failure, we deduced that something was horribly wrong. The long and short of it is, I was hoping that the collective experience and knowledge on this forum might be able to give me some insight as to what could cause this sort of failure? The cam is a W-120, with single high-rev valve springs, on a mild-compression (8.5:1) 1914 with 40 X 35.5 044 heads. The make of lifters is as-of-yet unknown, and the case was a dual-relief B series case. Mostly I'm looking for ways to prevent this from happening again on the next version of this motor, possibly with more cam, heavier duty valve springs, and more compression. Any help is greatly appreciated!

[richie]

How are the lifter faces? and also check the valve seats in heads for signs they were getting beaten? personally I don't think H/D single springs is enough with a 120 if they are normal weight lifters and steel or chromoly push rods and steel valves. Its most likely this damage was caused by valve float but there are other possibilities

How much clearance between back of head of lifter and case was there at full lift?

[Udo]

Pictures would be better

[andrewlandon67]

I haven't yet had a chance to crack the case, all the damage I've been able to look at so far was just checking through the cylinder holes in the case. I'll try to get the case apart sometime in the next few days and get some pictures to better show what I'm talking about.

[Udo]

How much clearance between back of head of lifter and case was there at full lift?

this can be the problem , what richie sayed

Udo