[Everett#2390]

Originally Posted by cstraub

Alot of times crown is not correct on the lifter nor taper on the lobe. It doesn't matter what you do it is going to fail.

Lack of truth in the first statement gives results of the second sentence.
Got to have lifter crown WITH lobe taper for this set-up results in the lifter and pushrod turning in the lobe rotation except at the lobe nose, the point of max lift, then the lobe has center contact on the lifter crown, the point of max pressure on the lifter from the valve spring.

[Steptoe]

Originally Posted by cstraub
Alot of times crown is not correct on the lifter nor taper on the lobe. It doesn't matter what you do it is going to fail.

OK lets think about this....IF the crown did happen to be off or the taper incorrect then the issue is still NOT with flat cam design or use...it is with the machining of the lifter and the machinist grinding the cam...Therefore one cant blame or put it down to the flat tappet cam....
And the only time I have seen either a lobe wrong or lifter faulty, was a cam we got ground for a sb chevy and the thing poped thru the timing cover
The reason for this was each alternate lobe is grind with opposite taper..this in effect centers the cam and stops it walking either way....A Ford cam, the tapers are all the same and has stops to stop the cam walking....they machined the tapers for a ford.

[cstraub]

Originally Posted by Steptoe

OK lets think about this....IF the crown did happen to be off or the taper incorrect then the issue is still NOT with flat cam design or use...it is with the machining of the lifter and the machinist grinding the cam...Therefore one cant blame or put it down to the flat tappet cam....
And the only time I have seen either a lobe wrong or lifter faulty, was a cam we got ground for a sb chevy and the thing poped thru the timing cover
The reason for this was each alternate lobe is grind with opposite taper..this in effect centers the cam and stops it walking either way....A Ford cam, the tapers are all the same and has stops to stop the cam walking....they machined the tapers for a ford.

I get a unique perspective on this industry since I supply parts to many manufacturers for their product lines. Demand is still there for flat tappet cams because of the realtively low cost. Supply now comes from other sources of shore and the flat tappet cam of 15 years ago is not the same as it is today. Neither is the flat tappet lifter.

If the cam goes down, one really needs to pull the engine apart and see if the debris got to the bearings. Once one takes all the precautions and then puts the 2nd or 3rd flat tappet in the engine one could have put a roller in it and been grinning from ear to ear while burning up the roads.

[Steptoe]

Talking to the guys who grind my custon cam designs...yep they have failures...
So i asked a qustion, "are they private guys putting engines together or experianced workshops that intially fire up their engines?"
A little thought.then "funny u ask that we where talking about that a little while back..it the private guys, nothing from experianced workshop, except where they build a short block for a customer."

[larryh56]

I have an update for you guys and thanks again for the replies - it has been interesting to read. When I took the valve covers off this is what I found.
It looks like the lock on the #6 exhaust valve backed off and the rocker turned sideways. Once the exhaust valve stopped opening the charge had no where to go or the pressure held both valves closed and the push rod on the intake side bent. There does not seem to be much other damage. How much do you think I should tear apart? I am thinking of replacing the locks, checking the compression in that cylinder, replacing those 2 push rods and possibly the stud that shows a little wear and trying again. The top of the valve stem is very slightly roughed up on the intake. The guide plate held the push rod in place so it does not look like it contacted the head at all. Turning the motor over by hand the lifters are still going up and down on that cylinder (and the rest) like they should so I think the cam may be good. Time will tell...

[Steptoe]

A few yrs back my engine sorta did that...
1 stock lifter...yep Im still running the orginal factory tappets ...dropped of the side of the valve, and had a bent lifter.....
The lifter never sat quite straight on that valve...No guides orginal push in heads...
We never figured out why that lifter #4 pot from memory, did not sit strat.. measured every damn thing, even thinking a valve guide was reemed off center but no...
But it clunked like hell....replaced the lifter and bent push rod good to go....
10 miles , nothing out ragious...did it again...
1st time was towing one of my vintages...still a good 40 miles from home..clacked all the way and didnt miss a beat.
So Drove back to the workshop....cant rem what they are called...later model 1:5 steel tappets and have a dipple each side of where it sits on valve....thru one out of the spares bin...and another push rod...
Still doesnt miss a beat.

Then about 12 yrs or so ago, a push rod went thru the tappet lol.....that clacked REAL load lol..had no choice but drive thru the main street... Threw another push rod in , tappet..
Yep got any bits...Oil and filter change

[Garfields Maro]

Pull those 2 lifters out and have a look. Sorry to say, but worn lobes still seems possible...and may be the culprit. Really need to figure a way of accurately measuring the lift compared with other cylinders....

[Steiner]

The VR1 oil only has 1000ppm zinc. Enough for stock type flat tappets and spring pressures, not so good for a more aggressive lift cam. With the intake off like that you can pop the lifters out and see the cam OK through the pushrod holes and also feel the lobe.

[Everett#2390]

As Steiner suggests, you can pull out the lifter and look at the crown of the lifter checking for a normal 'circular' wear pattern. If there is a divot, check lobe and go from there as to replace camshaft or not.

Loose locknuts will produce bent pushrods. My suggestion is either get new mechanical locknuts, no Nyloc's, or visit a fastener store and get jam nuts.

Jam nuts are half the thickness of a regular nut and use jam nuts in addition to locknuts.
Polylocks would work, but using them would be dependent upon the stud height and valve cover clearance.

[cstraub]

I would also suggest getting rid of those welded ball pushrods. They are a nightmare waiting to happen. Go with a a good 1 piece pushrods.

I also agree on pulling the lifters and checking the camshaft.

[eyecell007]

I would error on the side of replacing the cam/lifters as that's a relatively inexpensive job and not too much more time given how far you've already done the tear down.

[Steptoe]

Really need to figure a way of accurately measuring the lift compared with other cylinders....

Its not hard..a machinists dail on the back of the lifter and compare to another couple lobes...between a cam degree plate and measuring the cam lobes one can get the complete profile of a cam lobe and its postion... Its not rocket science or expensive stuff...Hell a chines dial these days are only a few bucks and the magnetic base about the same.....good enough for jobs like this....