Lifters, maybe? ... Probably

[Astro]

Hey guys,

96 L31 here. Super stoked about this, but I've got a consistent soft ticking sound coming from the passenger side. Seems pretty common.

Started after I changed the head gaskets and has been going on since then. Damn it's almost been a year. Initially I chocked it up to exhaust leak so I left it alone. Changed the manifold gaskets and, well, there WAS a leak, but after plugging it up, it only made the tick more noticable !

Took valve cover off, visual inspection was good. Valve lash was good, but adjusted anyway while running. Backed off until tick was audible, tightened until it stopped and another 3/4 turn. Of course one of them had to start squirting oil profusely. Hopefully fix that with an engine clean. Also used my stethoscope, pre adjustment, to try and narrow down ticking location, but found that all of them made a little noise, but not much and nothing was terribly obvious. One of them made a noise I didn't expect. I put my stethoscope on the stud of the first rocker arm and heard a very light knocking sound which made me very worried. Nothing seemed wrong with it mechanically and no adjustment seemed to change the sound. Also it wasn't the same sound, so I don't know.

Anyway, slapped it back together and the soft ticking is inexplicably more noticable with it all together, in the cab. It increases in frequency as I accelerate, quiets down a little at idle, but still noticable. Kinda stumped, but I think maybe I know what it is, but don't want to accept it. Bad lifters. I'm pissed because I could've replaced them when I did the heads, but didn't forsee this.

One thing to note, I'm running 5w30 on a possibly old motor. I'm not sure what the mileage is unfortunately. Guy I bought it from said engine was replaced, but he didn't know how many miles. He guessed around 150k. Odometer says 270k. When I had the heads and intake off, vlcenter valley was clean as a whistle, so I assumed low mileage.

All this to say, I'm running marvel mystery oil in the crankcase right now to try and clean any sticky lifters, and then dropping some rotella 15w40 in there.

Engine runs wonderfully otherwise. It sucks because I JUST finished a 4L80 swap and can't afford to drop another couple hundred on this. Was thinking of just saving up and getting the L29 I've been wanting.

Thoughts/advice anyone?

 

[SAATR]

Running MMO in the oil, or a similarly thin fluid like ATF, would have been my suggestion. Being that you have already done that (possibly with no change) and checked the lash adjustment, I would say that you're left with disassembly and inspection of the lifter(s). It's possible that some trash got into the lifter body during your head job, but equally possible that there's a internal defect in the lifter, or a problem with cam lobe and/or lifter roller/trunnion. A close inspection of everything starting with the rocker, pushrod, and pivot ball is my suggestion. If you don't find damage or wear in those components, move along to removing the intake and pulling the lifters. You should be able to disassemble, clean, and reassemble them if no damage is found in the cam lobe and roller. Pay close attention to the plunger and internal lifter body for scoring or other wear marks.

Also, I would suggest running a 5W40 instead of a 15W40 for cold flow and pumpability. Gives you the low temp flow characteristics of 5W30, with slightly higher hot viscosity to help with oil pressure. I've run it in both my L31's for the last ten years or so.

 

[L31MaxExpress]

The lifter probably got some trash or sludge in it. Give the MMO some time to work. I prefer Risoline myself, but MMO basically does the same thing.

The L29 is a great engine overall and this is just my opinion, your budget is not allowing a lifter swap now. A big block build is much more $$$$ than a small block and the big block will use more fuel. Not only do you have to buy a L29 if you do not already have it, but it will likely need to be gone through and then it will take a whole mess of parts to get it installed and running unless you have a complete, running donor truck. Be overly sure you want to go down that rabbit hole before you get into it.

Probably more budget friendly to merely swap some decent lifters into the current small block. Also consider that a mildly cammed 350 will actually surprise most power wise and it will actually make more horsepower and similar torque compared to a stock or near stock L29 anyway. The 454 Vortec was rated a whole 290 hp and 410 ft/lbs and only puts down a killer 230 hp at the tires. The L31 Marine engine makes 300 hp and 400 ft/lbs. Personally, I would run a little more cam than the GM 6395' in the Marine L31.

Summit 8800 looks like it would be a strong runner in an otherwise stock L31. Get the matching Summit branded Morel lifters while you are at it. If your heads were updated with better valve springs and the pushrod holes were opened up a bit, could also run a 1.6 rocker with that 8800 cam for a bit more lift. That cam is 204/214 @ 0.050, 0.450 lift on a 112 LSA. With a 1.6 rocker that cam is more like 206/216 @ 0.050 and 0.480 lift. The Stock cam is 191/196 @ 0.050, 0.412/0.428 lift, 111 LSA and the 6395' 300 HP L31 Marine cam is 196/206 @ 0.050, 0.431/0.451" lift on a 109 LSA. I feel the 8800 would match very well with the L31s static compression ratio and intake manifold. The 204/214 lobe "RV" cams have always worked very well in otherwise stock engines to give them a bit more torque and horsepower without having to rev them to the moon to see the added power. They give a very slight amount of lump to the idle compared to stock, without hurting drivability in any way. The torque curve remains similar to stock, there is just more of it everywhere.

 

[Astro]

I've only run the MMO for about 75 miles so far and their website recommends 300-500, so I've got some time!

I forgot to mention I put 1.6 rockers in it when I did the heads for that added lift. Thanks for the info on the different setups L31Max, I will look into them.

I'm really hoping I can pull a few more thousand miles out of this setup. The engine is strong, just noisy. The noise is super annoying though D=

I certainly hope I didn't damage the cam lobes. How would that have happened anyway and how would that look performance wise?

 

[sntrym]

Does it get louder or more noticeable in gear? If so, it might still be an exhaust leak. Otherwise let the MMO do its job and clean everything up.

 

[grey wolf]

What new parts did you install when you did the head gaskets? Did you have the heads rebuilt? One of the first engines I ever built was a 350. I had installed new valves and everything was fine for a while, then one day it started making a ticking noise. I took the valve covers off and found that a couple of the valves were damaged at the top, where the rocker arm contacts. To be honest, they were just cheap valves (I was a broke student at the time) and it appears that the top of the valve had broken off somehow, almost like the manufacturer had glued a hardened piece of steel to the top of the valve instead of making the whole thing out of good quality steel. I even found a couple of round pieces that had broken off just sitting on the top of the heads!

Anyway, I took the heads off and sent them back to the machine shop, where they rebuilt the heads again for free! Noise was gone and never came back after that.

The only other thing I can think of is, could the noise be associated with the 1.6 rocker arms? Maybe you have a bad spring that couldn't take the extra lift? I've never swapped rocker arms like that before, so I'm not sure what could potentially happen. Seems to me that it would add some stress to the valve springs.

 

[GoToGuy]

When you had the valve covers off and the engine running, you felt all over the valve train and nothing felt , or had vibration, noise different then the rest? Nothing stood out as " that doesn't feel quite right?"

 

[Schurkey]

96 L31

I put 1.6 rockers in it when I did the heads

SELF-ALIGNING rockers? If not, you need to stop running that engine NOW, before the real damage happens.

Did you verify clearance for the pushrod against the openings in the head that the pushrod pokes through?

Maybe you have a bad spring that couldn't take the extra lift?

Springs, and retainer-to-seal clearance.

 

[Supercharged111]

I'm getting away with .460"/.480" lift on stock springs, but I had to knock new seals all the way down to get the clearance. I think you're not supposed to put them all the way down on these engines. So it can't be the springs, but everything else you just laid out needs to be checked yesterday.

 

[Astro]

Clearances are good. DEFINITELY self-aligning 1.6 rockers. There didn't seem to be anything that looked or felt off which is why this has been particularly frustrating haha. Just that one rocker making that slight knocking sound that through me off that I mentioned in the original post. It's not the same sound I hear when I'm driving it though.

I know its hard to figure this out because y'all aren't here to hear it for yourselves, so I appreciate you guys at least throwing ideas my way.

The pushrods aren't touching the guides, that's for sure. They get close, but don't touch.

Also, it's a consistent tick at idle and throughout. The only thing that changes really is frequency. It doesn't really get louder or quieter. Just faster as rpms increase.

I'm not sure about the springs, except that visually, they looked good. None of the valves floated or anything. Just open close, open close. They all moved the same way too. None of them stood out.

When I had the heads off I took them to a reputable machine shop and had them go through them completely and they came back good. Pressure checked, seals checked, the whole 9 yards. All they had to do was a cleaning, inspection, and make sure the mating surface was flat and ready to go.

So the only thing I changed were the rockers. I fully inspected the pushrods too, when I had them out. I didn't remove and inspect the lifters unfortunately. Ugh I wish I had.