Noisy lifters?

[BPR Speed]

I've lashed rockers multiple ways but the best for me has been to warm the engine up to operating temp, cut card board to the length of the head, pop the valve cover off, slide the card board into the space between the valve springs and the outside edge of the head, slowly back off each rocker one at a time until the lifter and rocker seat start to tick (engine running). Then tighten the rocker back down slowly until the ticking stops then give it a quarter to half a turn (depending on your preference). I prefer a quarter turn on all rockers but internet arguments usually ensues after that statement as everyone is a hotrod specialist these days on the choice of a quarter, half or full turn on the rocker nut. The cardboard keeps the oil coming from the pushrod and the rockers from splashing off onto the exhaust manifolds causing a smoke show. I've always conducted a leak down and compression test while I'm there to check the seal of the valve seats and piston rings to cover my A**. I lash rockers off the base circle of the cam only when I rebuild engines and the block is out of the vehicle as it's convenient to visually ensure the lifter is actually on the base circle of the lobe and I can jiggle the push rod to verify the rocker, push rod and cam are at zero lash for hydraulic lifters then add my specific preload turn to the rocker nut.

 

[LVJJJ]

Aha, thanks Desert Old Guy, when I pulled the valve cover it had standard rockers so I thot I didn't get the roller cam. But thanks to DOG, mabe I did. However, the knock or tick was not any of the lifters, just not sure what it is. Since it goes away after it warms up, guess I'll just have to live with it. Has lots and lots of power, so maybe has roller cam. I'll have to call S&J engines again and ask about the cam, otherwise I need a refund.

 

[Insert Quarter]

Aha, thanks Desert Old Guy, when I pulled the valve cover it had standard rockers so I thot I didn't get the roller cam. But thanks to DOG, mabe I did. However, the knock or tick was not any of the lifters, just not sure what it is. Since it goes away after it warms up, guess I'll just have to live with it. Has lots and lots of power, so maybe has roller cam. I'll have to call S&J engines again and ask about the cam, otherwise I need a refund.

Forged pistons? Normally they make some noise until the pistons/engine warm up.

 

[Schurkey]

Some of the noisiest pistons I know of are the supposedly tight-fitting hypereutectics.

GM has had issues for years with piston slap due to the pistons they've selected.

 

[LVJJJ]

even tho I started this thread some time ago I should report that I did get the rocker cover off without removing much, took some muscleing. Adjusted the valves but they really didn't need it. Knock still there, fairly loud when cold but completely goes away when up to temp. Must be okay cause when towing and really gettin on it, the knock or tic isn't there. If it was a serious problem one would think that under heavy load it should make noise, doesn't. So, just drive it I guess.

 

[Schurkey]

Knocks when cold, goes away warm?

GM's infamous piston slap?

 

[Supercharged111]

Some of the noisiest pistons I know of are the supposedly tight-fitting hypereutectics.

GM has had issues for years with piston slap due to the pistons they've selected.

Wasn't that a case of blocks on the big side and pistons on the small side of spec? My 1500 has done it before in the winter. It's completely random too.

 

[Schurkey]

Wasn't that a case of blocks on the big side and pistons on the small side of spec?

No, at least I don't think so. The hypers fit tight, it shouldn't be a clearance issue.

Modern GM pistons have really short skirts. Less friction...but maybe they pound back and forth as they switch from minor to major thrust, and then back to minor as the crank spins.

But what do I know? Hypers shouldn't slap, but they do. Even aftermarket Keith Black hypers slap for fifteen or twenty seconds in my El Camino.

And imagine my surprise when I read my post from May. I'd forgotten all about that.

 

[Erik the Awful]

Sounds like piston slap to me. I believe it was an engineering / cost cutting issue for GM. I hope y'all don't mind a little story time.

No matter how precise you make your tooling, there will be wear, and your pistons and bores will vary in size. The generic spec for bore/piston tolerance on a small-block Chevy is between .0015" and .0045", which is pretty sloppy. If you're on the >.0040" end of things, you're probably gonna have some piston slap. If you take your engine to have it blueprinted, your machinist is going to take your brand new pistons, measure them, and carefully machine your engine's bores .0020" (depending) over that. It's tedious, but worth it for performance and long-term reliability. If it tells you anything, thirty years ago the specs were .001" to .004" - it's only since then that machinists have really started targeting that fourth decimal.

Starting in the 1960s, Cadillac started blueprinting their engines at the factory. Being an industrialized setting, they needed a way to standardize the pistons and bores instead of tediously machining the bores to fit whatever size the pistons turned out. They solved it by measuring the pistons and stamping a grade on them, then measuring the bores and stamping a corresponding grade on them. When assembling they simply used a piston that matched the bore size. If I remember right, they had fourteen different piston grades, each .0002" larger than the next. If you ever rebuild an engine and find a letter or number stamped next to the bore, inspect the pistons for a corresponding stamp. If you re-use the pistons, be sure and put them back in their original bores!

The Japanese manufacturers picked up on this way of blueprinting engines and used it in every engine, not just their luxury vehicles. The '90s era Nissan hardbody V6 pickup engines were blueprinted at the factory with (IIRC) four piston and bore grades. Then their piston supplier mis-marked a batch of pistons. The factory Nissan warranty was 60,000 miles, and the engines would start ticking on really cold mornings at around 50,000 miles. Nissan extended their warranties to 100,000 on their V6 pickups, and if your engine started ticking, it was a free replacement. I was a Nissan tech at the time, and I replaced a couple engines because of piston slap. It blew my mind because the Chevy pickups on the used car lot all had piston slap on cold mornings. Nissan took their image that seriously. They were also $200 million in debt and spending money like it was their last chance (it was, Renault bought them out a couple years later).

 

[Jesse_Wenting]

So I adjusted my rocker arms when I swapped my engine a couple years back to 1/2 turn past zero lash. Been a bit of valve train noise ever since. Last summer I tried re-adjusting with the engine running and the valve covers off but the whole engine started running rough so I stopped, worrying that I could be hitting my valves with pistons. Since then I think I heard somewhere that it was actually something to do with the lifters

Since I know every single valve is a half turn past zero lash, would it be safe to just take the covers off and add 1/4 turn to each one and then let the engine run for a bit so the lifters figure themselves out? (maybe twice if they're still clacking after the first try?)

Bone stock 98 305, been running pretty good for about 2 years & 30,000km. Original roller hydraulic lifters, unknown condition and would prefer to not open the engine (Don't mind taking the intake off, but I don't wanna drain coolant again)