[tooski]

Because of all the loose rockers, I took the intake and valley pan off to check the cam as I thought I lost lobes. The lobes all looked the same and good (compared to the pics I've seen here). I checked the lifter bottoms for wear. None evident and slightly convex. I disassembled and cleaned the lifters. Reassembled the engine and because of the aluminum heads set the preload to 1/3 turn instead of the recommended 1/8 for these lifters. Obviously I failed to properly tighten one down as after a warm up and run up to 3500 a loud tapping reoccurred. Engine started to miss with a pop in the exhaust. Fouind #8 exhaust extremely loose. When I reset it I saw the exhaust valve start to open when I expected the lifter to start depressing. I restarted the engine. No more tapping, but the miss and exhaust pop remain. Engine will not idle.

Is this lifter now 'pumped up' and acting like a solid and holding the exhaust valve open?

Apparently I require an in depth tutorial on the operation of a hydraulic lifter further to the info on the web.

Oil enters the lifter through the main body oil hole and then into the plunger cavity via its oil band and oil hole. Some oil enters the push rod via a metering plate. Other oil enters the main bod cavity under the plunger via a one way check ball/plate (mine has the plate). Once that cavity is filled I see very little 'cushioning' effect as the only escape route is the tight tolerance between the plunger and body. The only way I see a lifter taking up lash is when the valve is closed (zero pressure on the lifter), lifter on base circle and the oil pressure entering the lifter pushing up the metering plate/push rod cup, stroke distance limited by the retaining clip/spring and preload,

I assume the only purpose of the spring is to keep the plunger at the top during preload adjustment when no oil is in the lifter.

[zippy]

I would take that lifter out, dissasemble and clean inside parts. Could just be varnished up. Yes, the leak down is mostly through parts tolerance and oil up the pushrod. Also check your pushrod hole is clean and free of gunk. Lifter lube hole too

[Formulajones]

What hydraulic lifter are you running that only requires an 1/8 turn?? That's not much preload at all, and I'd expect any hydraulic to be noisy with that preload.

Since your valvetrain is adjustable I'll assume you're using the go to BBC 7/16-20 rocker stud. 1 full turn on that stud only yields .050" preload. 1/8 of a turn is only going to get you about .010-.012" at best, and that's hardly anything. Even 1/3 of a turn is only going to get you maybe .020" which still isn't much preload to speak of. Factor in aluminum heads and you're going to lose several thou of that preload as well.

[77 TRASHCAN]

I’m wondering what brand also....

1/2 to 3/4 turn is what I read here, from experts.

[Dragncar]

I sure hear about a lot of problems with hft and hyd roller lifters.
I gave them up a long time ago. sft and solid roller for me. if you go SR get the BAM steel bushed lifters with DLC coating.
You do not have to adjust solids all the time like some think. Use good parts and equipment and set them up right and they hold their lash for a long time.
Many stock engines run solid lifters. Nothing wrong except them being better than hyds in almost every way.
Only time I have ever had a problem it was with hyd cam and lifters.

[Formulajones]

Originally Posted by 77 TRASHCAN

I’m wondering what brand also....

1/2 to 3/4 turn is what I read here, from experts.

Yeah, and a 1/2 turn will only yield .025" preload with those studs, and that's just not a lot of preload, especially when you're running an aluminum head.

Most lifters require .030 to .050" of preload, the latter is 1 full turn on those rockers. Add a pinch more for aluminum heads for the preload lost when the engine is warm.

[tooski]

The lifters are H-O Racing VL-12. Purchased cam, lifters and springs in 1990. I do not know what make the lifters or springs are. I don't know how I found out, but the cam was made by Crane to H-O's specs. The instruction sheet that cam with the lifters recommended zero lash for racing and 1/8 turn.
Back in the late 70's I acquired a publication that stated for a 'free' 500 more rpm to change to an adjustable valve train and set to zero lash (kind of silly for a non performance engine done by 5K or sooner). As my stock 350 developed a tick that I made worse by trying to adjust the non adjustable valve train I installed poly locks at zero lash. Ran that way until I had a 400 built in 82. Ran that at zero lash until the H-O stuff in 90. Ran that for several years at 1/8 preload. All of the above on 7/16-20 studs.
The current engine was machined around '98/'99. It came back with all the frost/ gallery plugs installed. I assumed it was cleaned properly and ready for assembly. With a bit of grit in a couple of the lifters I am thinking not and the sludge is now loosening up and circulating.
I'll try increasing the preload for now, but I am resigned to removing the engine for an internal cleaning.

[Mike Fowke]

Is this lifter now 'pumped up' and acting like a solid and holding the exhaust valve open?

If you saw the valve drop while adjusting, I'd say yes. I'm just a hobbyist here, but I'm surprised you moved the valve with such little preload. Are you sure you didn't add any pre-load when taking the slack up on the pushrod?

You might try bringing the piston up, put some air in the chamber, and try again. Hope this helps.

[Scott65]

Comp Cams used to offer a limited travel hydraulic flat tappet that was set with very little lash. I can't remember exactly, but I think it was between .004-.010" hot. Seems like I remember setting them around .012" cold with aluminum heads. They worked well. MUCH better than the current stuff.

[Schurkey]

Originally Posted by tooski

When I reset it I saw the exhaust valve start to open when I expected the lifter to start depressing. I restarted the engine. No more tapping, but the miss and exhaust pop remain. Engine will not idle.

Originally Posted by tooski

TThe instruction sheet that cam with the lifters recommended zero lash for racing and 1/8 turn... ...Ran that for several years at 1/8 preload... ...I'll try increasing the preload for now, but I am resigned to removing the engine for an internal cleaning.

The folks who sold the lifters say zero to 1/8 turn for preload. You clearly have short-travel lifter plungers.

You ignored their advice, cranked 'em down too far, WATCHED THEM HOLD THE VALVE OPEN, and now the engine doesn't run right.

Did you ever take a cranking compression test? I bet you're near-zero on the cylinders that have open valves.

And you think MORE preload is going to help?

Back 'em off, hope you didn't damage the cam. Enjoy. If the heads expand so much that 1/8 turn preload isn't enough...you're going to have noisy lifters because more preload will just hold the valve(s) open when the heads are cold.