Hi guys, I've been reading for hours about valve tick but wanted to start my own thread with specific details to my problem in hopes of making an informed decision on what to do. Here are the things I've found with the engine(1979 400):

-It has a loud tick from the valve covers. One day sounds like the drivers side, next day sounds like the passenger side.

-Removed valve covers and ran engine. Pressed on the rocker arms with a screw driver and on several of them it quietened them down.

-Listened with a stethoscope and can notice some are noisier.

-Looks like very minimal wear on the rocker arms and the pushrods and valve tips look really good.

-No smoke out the exhaust.

-Engine has 10 psi oil pressure when warmed up at idle. Good oil pressure when cold or going down the highway.

-Lifters are noisy no matter what the oil pressure is.

-Compression is 112-118 in all cylinders with 18" vacuum but leakdown is around 30% past the rings.

-Oil was not changed regularly(no paint left on the oil filter) making me think the lifters are dirty.

-Lifter cleaner in the oil did nothing.

Since I need to change the leaking intake manifold I though I would try a new set of lifters. My only concern is it might be ticking because of oil pressure or worn lifter bores. I could measure the bores before buying lifters.

If it was ticking from low oil pressure wouldn't it stop ticking when the oil is cold or when the rpm's are higher because the oil pressure is normal at that time?

If it was lifter bores wouldn't all the lifters be noisy rather than only a few? I would guess that lifter bores would wear fairly uniform. What should the bore to lifter clearance be? I have access to some mics.

So with my limited experience I think the problem is crudded up lifters from infrequent oil changes but I sure would like some input from someone with more experience. With even compression and good vacuum I would say the engine has a few good years left in it despite the low oil pressure. It's not a daily driver. The valve tick bugs me though and it would be crazy to leave it if all it needs is a set of lifters. Hope I didn't miss anything too obvious.

Thanks to all for the help.

 

That motor sounds worn out with the cylinder psi and oil psi you wrote. I think I would look for another one or completely rebuild it. For the noise, it would be a lot of work but you could check all the lifters preload and see where your at there.

 

Thanks Mark. I wasn't sure what the cyl pressure should be but figured it should be higher than that with a stock cam. I'm only using the truck as a spare for work when my newer one is down for repairs. I didn't consider lifter preload being out of spec as the rockers and pushrods look in such good condition. I didn't measure spring height but figured if the valves are sunk lifter preload would increase and not cause ticking. I'm sure the engine's never been rebuilt so no chance of someone messing up the preload. I'd like to drive it until the very end(knocking or dead cyl) but the ticking makes it sound like a real pos. The Chevy guys at work will never quit teasing me.

 

Found some numbers for lifter to bore clearance .0007-.0027 with a wear limit of .005 Does this sound right?

 

I had my driver's side rearmost rocker so loose you could wiggle it 30 degrees and the bolt was barely finger tight. After retorquing it to 20lbs it still ticks. When I pushed down on the lifter using the pushrod, it made a squishy sound not unlike squeezing the last bit of jelly from a Smucker's Squeeze bottle.

I figure the lifter's collapsed and it'll take awhile to free it up, that or I'm going to have a tick for a LONG time.

I am pleased to see my oil consumption cut back from 70mi/qt to 200-250mi/qt since changing the one valve cover gasket and re-torquing all the rocker bolts.

 

I need some valve cover gaskets myself and intake manifold. Rear seal is leaking some also but I'm gonna let that one leak.

I had to use this truck for work the last 2 days and the ticking has gotten much quieter. I think the clean oil is cleaning up the lifters. Now it sounds more like a typewriter clicking away instead of a few loud pronounced ticks. I figure the valvetrain noise now equals the worn bottom end so I think I'm just gonna drive it.