Broken Roller Lifter

[Dave Garner]

I have had a 'link bar' on the hydraulic roller lifters for No.1 cylinder come off the new (730 miles in use) Edelbrock roller lifter. The photos show:-

an overview of 7 of the roller lifter 'pairs' looking normal but the link bar is missing from the lifters on cylinder No. 1

detail of the 'unlinked' lifter pair. Note that the exhaust lifter has rotated 90 degrees (and thus 'machined' the lobe off the cam shaft!)


the 'missing' lifter link bar and one of the securing pins ( recovered from the bottom of the front sump)

Has anyone experienced a similar failure?

Dave
For info engine is a 302 with hydraulic roller cam, Edelbrock RPM performer heads, Edelbrock roller rockers and RPM airgap intake manifold.

 

[Jac Mac]

The broken link bar & pin is only the end result along with what is now likely a destroyed camshaft.
Possible causes could be one or any of the following in no particular order:
1. Valve sticking in guide allowing pushrod to 'jump' out of lifter and damage link bar etc.
2. Pushrod failure & lifter being pushed up to max travel of link bar and then twisting in lifter bore.
3. Incorrect spring choice for camshaft & valve train allowing spring to go into a 'surge' or resonance state and whole valve train becomes unstable.
4. Intake backfire @ cold start or during hard acceleration where the inlet valve will be lifted off its seat by the explosion, the hyd lifter then tries to compensate for the excess lash , valves can then touch piston, pushrod then bends as it is weakest link etc etc..
5. Over rev where valve train weight cannot be controlled by the valve spring, same scenario as #4.
6. Possibility of the roller failing on the lifter if the engine build or lifters have no provision for oiling of the roller/cam lobe interface. ( Check out the CompCams website for lifter bore oiling mod & tool )

The metal that has likely been milled off the cam lobe will now likely be thru most of the oiling system...DO NOT skimp on cleanout of galleries at the rebuild.

 

[Dave Garner]

Thanks for 'the directions in which to look' Jac!

I have got engine to bits now and have some more info. so an update is worthwhite.

Taking the likely initiating events in order:-

1) I still have compression on No. 1 cylinder and there is no evidence of valve to piston impact, I have not yet checked if the exhaust valve is sticking though.

2) The pushrods from No.1 look to be OK (they 'roll true' on a flat surface and there are no signs of damage or blockage).

3) The Edelbrock RPM Performer Heads come built up with double valve springs to match the RPM Performer Cam - I used the closest Comp Cams cam (282XR) to the Edelbrock RPM Performer cam because I was not happy with the finish on the lobes of the Edelbrock cam when I inspected it prior to fitting. That should have avoided resonance issues, but resonance is a VERY specific thing so it cannot be definitively ruled out.

4) Backfire - I had a missfire develop above 4500rpm, (though not really a backfire) due to what turned out to be a broken rotor arm late on the day of the failure. However the damage should have been visible on the piston/pushrods of No1 cylinder but they were OK

5) Over-rev - always a possibility on track (and I had been on track 3 days that week) though I do try to be very careful to avoid it! Again however the damage should have been visible on the piston/pushrods of No1 cylinder but they were OK

6) The rollers on No.1 cylinder lifters are turning freely and look in remarkably good condition - particularly given that the exhaust lifter (the one that turned thru 90 degrees) 'machined' a ruddy great grove right around No.1 exhaust cam lobe!!!! So it looks like oiling was OK.

I am going to add a 7) which is poor manufacturer quality control on the part.

The link bar is undamaged, both of the securing pins had detached, one is in good condition other than that it has separated from the link bar and lifter, the other is 'mangled' having ended up in the timing chain where it was impaled on the cam shaft sprocket and eventually broke the timing chain (bending valves in No, 2, 3, 6 & 7 cylinders despite staying with 1.90" valves and stock pistons).

I think the above leaves 1) stuck exhaust valve, 2) resonance and 7) poor quality control as 'potential causes'. When I get the valve springs off No1 I will post an update.

Given that the engine has had a liberal dose of fine swarf and needs a serious and detailed clean out, I have quite some time to decide if I trust the remaining 7 'lifter pairs' - or indeed if I want to use roller lifters again at all! (seeing as I need a new cam shaft anyway..........)

Dave

 

[Jac Mac]

Dave, one quick way to check if your valve spring package has been 'Stable' is look at the end of the valve stems, with roller rockers the wear pattern should be clearly visible as a distinct line approx 0.060" wide across the valve stem end face ( or multiples of that wear pattern ), if you dont have those individual marks and the whole end of the stem is one polished circle it means the valve has been rotating in the guide at a fairly high rate and to do that the spring package has not been correct. I know this is contrary to what the OE manufacturers want in terms of valve seat life etc where they install all manner of 3 piece retainers etc in order to promote rotation, but for performance applications we have to rethink the problem.Once the cam stops turning while the crank is still spinning you will have the valve damage noted as any valve/piston clearance is only configured for the initial part of the camlift, not valve wide open on these engines ( interference design).

If your contemplating a flat tappet replacement the lifter oiling mod or some lifters with face oiling provision are a must.

One other thing, back in the old race days when using roller cams we fitted mesh screens over all the valley & head drainback holes to prevent any bits of debris getting in contact with all the moving bits downstairs... that need has not changed & I would advise anyone fitting roller cams etc to fit these, just think of how many SBF motors that have been damaged by the circlip out of a lifter finding its way into the oil pump alone!

Are the edelbrock lifters compatible with a comp cam... I seem to remember that there was a difference in the roller dias ??? Might be wrong on that, will have to check.

 

[John Fitzpatrick]

Jac-
You said: "If your contemplating a flat tappet replacement the lifter oiling mod or some lifters with face oiling provision are a must."
Could you explain that mod. you're referring to, and is it just needed when installing flat tappet cams in post 85'-86' 302 blocks? I don't understand how changing from hydraulic roller lifters to solid would effect the lifter oiling.
John

 

[Jac Mac]

This rough sketch is where & how the grooves are cut in the lifter bore ( Solid 'RED' line ) to provide cam lobe oiling, this is reqd where you use lifters that do not have oiling provision built/drilled into them. I think its Crower who make the 'cool face' flat tappet lifters and several manf make roller lifters with oiling provision, I made a couple of tools for cutting the grooves to suit chev & ford lifter bore sizes, they cut from the bottom up so you need the block stripped down to perform the task. Does it work? , put it this way I have not 'lost' a flat tappet cam/lifter since I started doing this mod several years ago and several of the cars/engines concerned have not been treated with the respect they deserve in regard to oil types & change routines and many are fitted to cars that get spasmodic use which in reality is the toughest thing you can do- park it up for say 3+ month's and then take it out & drive it like its stolen

 

[Rod]

Thanks for 'the directions in which to look' Jac!

I have got engine to bits now and have some more info. so an update is worthwhite.

Taking the likely initiating events in order:-

1) I still have compression on No. 1 cylinder and there is no evidence of valve to piston impact, I have not yet checked if the exhaust valve is sticking though.

2) The pushrods from No.1 look to be OK (they 'roll true' on a flat surface and there are no signs of damage or blockage).

3) The Edelbrock RPM Performer Heads come built up with double valve springs to match the RPM Performer Cam - I used the closest Comp Cams cam (282XR) to the Edelbrock RPM Performer cam because I was not happy with the finish on the lobes of the Edelbrock cam when I inspected it prior to fitting. That should have avoided resonance issues, but resonance is a VERY specific thing so it cannot be definitively ruled out.

4) Backfire - I had a missfire develop above 4500rpm, (though not really a backfire) due to what turned out to be a broken rotor arm late on the day of the failure. However the damage should have been visible on the piston/pushrods of No1 cylinder but they were OK

5) Over-rev - always a possibility on track (and I had been on track 3 days that week) though I do try to be very careful to avoid it! Again however the damage should have been visible on the piston/pushrods of No1 cylinder but they were OK

6) The rollers on No.1 cylinder lifters are turning freely and look in remarkably good condition - particularly given that the exhaust lifter (the one that turned thru 90 degrees) 'machined' a ruddy great grove right around No.1 exhaust cam lobe!!!! So it looks like oiling was OK.

I am going to add a 7) which is poor manufacturer quality control on the part.

The link bar is undamaged, both of the securing pins had detached, one is in good condition other than that it has separated from the link bar and lifter, the other is 'mangled' having ended up in the timing chain where it was impaled on the cam shaft sprocket and eventually broke the timing chain (bending valves in No, 2, 3, 6 & 7 cylinders despite staying with 1.90" valves and stock pistons).

I think the above leaves 1) stuck exhaust valve, 2) resonance and 7) poor quality control as 'potential causes'. When I get the valve springs off No1 I will post an update.

Given that the engine has had a liberal dose of fine swarf and needs a serious and detailed clean out, I have quite some time to decide if I trust the remaining 7 'lifter pairs' - or indeed if I want to use roller lifters again at all! (seeing as I need a new cam shaft anyway..........)

Dave

Hi Dave, was wondering how this played out