You and correct

Hydraulic rollers, not flat tappet....

 

Maybe the problem's root cause is in the Rhodes lifter. They achieve less "effective" lobe lift & duration by bleeding off oil pressure ... most notably at low rpm. Maybe the lifter bled off too much ... allowing too much pushrod-rocker clearance ... pushrod slamming around. Maybe the valve clearance on that lifter (maybe others too) ... Maybe root cause is lifter(s) adjusted too loose ... same result.

 

Jackson,you get the cigar... i think......i was talking to james last night and there seemed to be 2 related problems...the lifters were acting as you described and also the pressed in guides were ceasing to be pressed in......i think it is currently being reassembled which is why james probably hasnt had time to be on the forum.....john

 

John,
the problem which caused the pull down was valve guides. As I explained (or maybe I didn't) the guide was loose and slipped out of the head. My engine man heated the heads and 3 more guides were loose. The rest were tight. The 4 loose guides have been "O" ringed with steel rings and pressed back so they cannot move. He has guaranteed the other guides will not move.
I believe the sequence of events was
1/ guide slipped into intake port
2/ valve had no control so it moved around
3/ Rocker moved off the tip of the valve
4/ Pushrod hammered into the seat on the rocker smashing it

A new rocker and pushrod are being fitted as well as new exhaust valves due to cracks (lean condition sometime in the heads life)

The secondary problem I am fixing "while I am at it" was valve bounce.
I have replaced the valve springs with ones which fit into the spring seats. The ones which were there could move around. I have also upped the seat pressure from 120 to 150lbs. I am replacing the Rhodes lifters with quality anti pump ups in search of an extra 1000 rpm.

I just returned from picking up the heads and they are beautiful again. Hope to have everything back together before the weekend

 

Hi guys, Back again.
Just pulled the oil pump and there is some damage to the gears so I will be replacing the oil pump. the screen stopped the bigger lumps of metal but some smaller pieces have made it through, one of which is embedded in the gear face. some smaller scratches on the other gear faces. I have also pulled 3 of the main bearing caps and the bearings appear to be OK.

Now for the $64 question,
Do our engines have the full flow of oil through the filter or does some of it bypass? I believe the filter has a bypass if it gets clogged but I religiously change the filter and oil every 5000 miles and the filter would not get a chance to clog.
Ok, did a bit of research and Chevys have a full flow filter. all the oil has to go through the filter before entering the engine. I am not as worried now

I really don't want to pull the engine but if there is a chance some of this metal has made it to the oil galleries and will get washed down to the bearings I think it is the smart thing to do. I will be asking my engine man this question tomorrow morning.

Not happy Jan........

 

A new rocker and pushrod are being fitted as well as new exhaust valves due to cracks (lean condition sometime in the heads life)

The "lean" condition you mention above may be the single most important factor relating to your head problem. All the old time racers that used the early GM aluminum heads errored on the "rich" side to prevent heat related failures with these heads. G.

 

Happy Dude here,(just send $1 to 732 Evergreen terrace)
Just finished running in the new lifters onto the cam and will change the oil and filter when it cools down.
After that I will go through the lifter adjustments and reset the timing.
Not going for a test drive as it's pouring down here, that will have to wait but she seems to rev up a lot quicker with the new springs and lifters(maybe the timing is right ) Stayed cool for the 20 minutes at 2000 and the clutch fan works as it came in about half way through the run.

 

James,sounds like it is all good news finally.......john