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You may have some collapsed lifters. Not uncommon with made in Mexico/China lifters. Set that valve cover on there without the bolts, start the engine let it run long enough to get good oil pressure. Shut it off. Pull the valve cover and push down on the pushrod side of the rockers. If you can depress the plunger in the lifter, even a little it is junk.
What about the side-to-side movement of the rockers on the pedestals? Also, the inspection was done on a cold motor, so lifters probably weren't pumped up.
I don't think that the side to side movement is going to make much difference. The valvetrain is designed with the pushrod in plane so the rocker arm doesn't see much if any force to make it move from side to side. The movement you're seeing is entirely normal for this type of valvetrain.
Just for giggles I pulled the valve cover off of a 351C that I built over a year ago. It was last ran on 9/26/20. It got NOS made in the USA, Sealed Power HT900 lifters. They are still pumped up; in fact, they are still holding a couple of the valves open.
E-bay. Spark Surplus down in TX. had a case of old stock HT900's. I bought three sets and used them up. Wish I had bought more, but at the time I wasn't sure what condition they were in since they had some age on them. Turned out they were like new, but I did have to take them apart and clean the dried oil out.
A roller lifter will not run on a flat tappet cam core the surface and the shape of the lobe are not compatible and it would only last a few minutes.
Putting new lifters on a cam that's already broken in is a little risky. It isn't nearly as bad as old lifters on a new cam but break in will still be pretty critical.
Dave is 100% correct. You can't just change from flat tappet to roller lifters.
You need to do some serious diagnostics and determine exactly what's wrong. We can all sit here and guess, but you are the one who has to do the work.
First thing I would do is pull the oil filter and cut it open, look in the pleats for metal. There will always be a little cast iron fuzz in a new engine but if there are pieces in there with part numbers on them you got big problems.
Let us know what you find.
Last night I ran the engine for a few minutes, then checked the valvetrain again. All pushrods were the same as before - I could turn them by hand when the valve was closed, but none were the slightest bit "loose". Talked to a guy at the machine shop earlier this morning & he suggested ethanol gas could be causing intake valves to stick. Not sure about that, but for the cost of an ethanol-free fill up and a can of seafoam, what's there to lose? Will also replace oil filter & check old one for debris.
That’s a little more side movement in the rockers than it should be, are the pedestals aluminum or steel
If aluminum I’d replace them, worn aluminum pedestals was a issue we had with Cleveland’s and M engines back in the day
That’s a little more side movement in the rockers than it should be, are the pedestals aluminum or steel
If aluminum I’d replace them, worn aluminum pedestals was a issue we had with Cleveland’s and M engines back in the day
Pedestals are steel. I'm paranoid now, so will probably end up pulling all the lifters for inspection. Thinking I might as well replace the rocker assembly's while I've already got them off. Thinking about going with a roller rocker - is there a reliability case to be made there? I know in my application there's no performance benefit, as my truck is a 3/4 ton 4x4 & will never see more than 4500 rpm.
The original sled rockers are available new. You can get them at any parts house. I believe the Melling PN is 214-1078. They should be around $5-6 bucks ea. You get the whole thing rocker, sled and the bolt.
Roller rockers won't do much for you except empty your bank account. Your pedestals aren't machines for screw in studs and guide plates so your only choice would be adjustable Scorpion bolt on rockers, over $700 by the time you pay tax. Or a Crane kit for pedestal mount rockers, plus the rockers and maybe new pushrods.
Just figure out what's wrong, fix it and drive on.
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