AMC360 Rockers knocking

[Zephrant]

Bought a used 360, rebuilt it, put it in place of a straight six in a 81 Wagoner. Runs fine, but the rockers are knocking really loud. It doesn't sound right.

Hot tanked, decked, line honed block.
New valves and springs, flat top pistons, bearings.
New fuel pump, oil pump, oil pickup, timing set, HEI dist., timing cover, water pump, lifters, alternator, hoses, belts, Edelbrock air gap intake, Holley Street Warrior carb, air filter, fuel filter, fuel pressure regulator, valve covers, sensors, engine mounts.

Reused rockers, exhaust headers, starter, pressure plate. No special changes done for better oil flow.

Pistions: Wiseco Pro Tru Street Pistons PTS539A3 (Flat top)
COMP Cams High Energy Cam and Lifter Kits: K10-202-4 (High lift cam)
JEGS 20274 AMC Pushrods 7.794 in. Long 5/16 in.

I pulled the intake and verified the cam looks clean (pristine), and the lifters (also pristine). Replaced the lifters in case I damaged them somehow. Replied the rockers too. Still the same issue.

Watching a slow motion video, the valves knock when they hit full travel. But I measured their travel as no more than 13mm with a dial indicator and have 16mm between the keepers and the VSS. There was no indication of damage to the VSS or keepers on the valve that I inspected. Watching the video, it does not appear that the springs are fully compressing.

Other than replacing the cam with a normal-lift cam, or re-doing the heads with roller rockers, is there anything else I can check?

[Stuka]

Did you soak the lifters in oil for a while and work any air out before installing them? I wonder if maybe they not pumping up all the way.

[Srdayflyer]

did you PRIME the engine by running an old distributor with the gear removed and run with a drill motor till the engine is primed, if you havent you probably have dry lifters and running them till they "pump" up you may have caused internal damage to the lifters using assembly lube will only prevent damage to the cam and the lifter bores and cause the lifters to be damaged as they only have a corrosion preventative coat of oil. for packaging and storage. i have always primed my rebuilds , JMO

[Srdayflyer]

did you check the pushrod length between the new and old OEM pushrods as the issue may be that the "new rods may be too short if even only by a few thousands , i ran across that when i rebuilt my 232/6 and had a hell of a clatter and they were only off .020 not much but enough, i would verify that as well

[Zephrant]

I did prime the lifters with a drill until I had oil at all of the rockers. I did not pre-soak the lifters in oil.
I was worried about maybe having damaged (or bad) lifters. I did replace the CompCams lifters with (maybe) better quality Elgin lifters. Primed again, does the same thing.

I've measured the pushrods at least 10 times, so either I'm constantly wrong, or ???
Would not be hard to try shorter ones now, valve covers are off at least. Hate to keep throwing parts at it though.

[mojozoom]

That's only 0.031" more lift than the stock cam. My guess would be that the retainers are hitting the top of the valve guide. You could replace one spring with a light checking spring and turn over the engine slowly to see how close it gets.

[Srdayflyer]

with the pistons at tdc do you have any play? there should be no play between the rocker arm and the valve stem face, these are zero lash motors and there should be no play as the lifters should maintain pressure unless there is a failed check valve in the tappet allowing insufficient pressure preventing zero lash and rocker arm clatter

[Zephrant]

There is no play at TDC on the rods. They are also all rotating normally when run.
I did pull a spring and inspect the VSS and keepers. No indication that they are hitting. I measured movement of the valve (by the cam) at 13mm, and there is 16mm between the VSS and the keepers.

Looking at a slow-motion video, the springs are not fully compressing, and I think I see the keepers stoping before they reach the VSS.

But I'm still not understanding the knock at full extension.

[Zephrant]

Pictures from cyl1 intake spring:

[devildog80]

Yes, saw you put in a new oil pump, but what is the pressure running?

[Zephrant]

Pressure reads at 40psi on the dash gauge at idle. 30w Lucas break-in oil.

[Scotty54]

Making any progress? I am really interested in this as my son has a similar problem with his rebuilt 258.

[Zephrant]

I pulled the spring from cyl2 exhaust. The rocker and valve can move down 16.5mm before the keepers tough the VSS. But normal lift on the CAM is only 13mm, so I am not bottoming out the keepers.

Without the spring, the rocker appears to be able to move from slightly lifted from the valve stem, to 16mm valve down, so again, longer range than needed.

Took some more slow-motion video, still can't tell for sure, but it sounds like the exhaust knocks just when it starts to recover from full extension (piston should be down?). The intake knocks as the valve closes (again, piston is at the bottom?).

[Zephrant]

Here is a slow motion video: https://youtu.be/eH7-JeFgKSk

Ignore the no-oil on the exhaust lifter, I has just installed the adjustable pushrod and started the engine, oil had not filled it up yet. I checked later, and it's oiling the same as the other ones.