Strokinit383

iTrader: (22)

I recently developed a lifter tick in what seems to be my #1 cylinder. JY 5.3 longblock, with xer273hr-14 cam, PRC dual springs and new LS7 lifters.

Cam specs: 224/230@114 .581/.588, XE-R lobes

Initially I was running comp magnum 7.425" pushrods. Car ran great, valvetrain was quiet, no problems. Began a few idle tuning sessions, logging airflow and letting the engine heat up to 220 degrees or so. On roughly the third session, one of the lifters for the number one cylinder (i suspect) began to tick. It will stay quiet regardless of temperature until I blip the throttle, then it begins to clatter away. The tick will not go away regardless of rpm or temp when it begins. I used a large screwdriver to pinpoint the location of the tick. I can also hear it out the exhaust, which makes me suspect it is the exhaust valve lifter. This is not a faint tick, it is very loud and noticable.

I began to question my lifter preload, so I used a pushrod checker to find the length at which I was at 0 lash and 22 lb/ft, measuring at the base of each lobe. I double checked each measurement by reinstalling the 7.425 pushrods and using the turn method. Both measurments matched up. Cylinders 1, 3 and 5 were measured. Each valve on these cylinders was close in length when finding zero lash - roughly 7.3 inches. This meant that I had .125" of preload!

Comp recommends 7.4" PR for this cam, which still seems to be too much. From everything I've read, the LS7 lifters like to be around .080 but others have recommended .050 as the ideal measurement. This would mean I would need between 7.35-7.38" pushrods. This seems a bit contradictory to what should be happening. Since the base circle of the cam is smaller, I would have assumed that I would need a longer pushrod. Just for the hell of it, I through in the stockers at 7.38". I fired it up and let it run for about 30 seconds, plenty of time for the lifters to pump up. With the stockers, it was clattering like crazy from what I'm assuming was way too little preload.

What is happening here? What am I missing?

Thanks in advance for the help. Sorry for the long read.

crainholio

iTrader: (2)

You missed posting your pushrod checker measurement at zero lash w/ lifter on the cam's base circle. Can't help much without it.

edit: "Roughly 7.3 inches" doesn't get it done, need a measurement out to 0.00x" to be of any use.

Strokinit383

iTrader: (22)

Right there. At 7.3 inches I was at 0 lash. PR checker is 6.8" + 10 rotations. Verified this with a set of calipers.

Strokinit383

iTrader: (22)

I said roughly because each cylinder and valve was a tad different. They all ranged from 9.75 rotations on the low end to 10 rotations on the high end. Making the distance to 0 lash between 7.2875 and 7.300 inches.

crainholio

iTrader: (2)

Original post said "roughly 3 inches"...but if you're certain it was exactly 10 rotations on the tool then 7.300" is the measurement.

Assuming LS7 lifters, I'd go with 7.400" pushrods.

Not sure why your stock pushrods were noisy as they should be just barely within preload range.

Did you tighten your rockers using the GM procedure so the lifters were on base circle, or run 'em down all at once and bottom out several of your lifters in the process?

Strokinit383

iTrader: (22)

As far as using the word "roughly," see above post. I was a little perplexed as well. Each lobe was torqued individually on the base circle. Each PR and rocker was checked as well.

When started, the engine was hunting for an idle and eventually died. It didnt pick up and idle like it should/did before the new pushrods. I appreciate the insight.

crainholio

iTrader: (2)

I'd get a set of 7.400" Comp or Trend and go from there, hoping the noisy lifter wasn't hurt while running the longer pushrods.

Strokinit383

iTrader: (22)

Thats my fear. Correct me if i'm wrong, but if I collapsed a lifter I wouldnt have any play at zero lash. Should the measurement to 0 lash be much longer if it was collapsed? I was able to compress the lifters a tad by hand. Each felt normal. I have a set of 7.4's that should be at my doorstep today. Will see how the engine responds with those. Thanks again.

therabidweasel

iTrader: (5)

I don't even really see a problem with 0.125. I briefly picked up a tick with my YT rockers hitting the steel baffle in the oe drivers valve cover. If you bottomed the lifter it would eat itself in a real big hurry, you weren't even close to bottoming.

That said, I am always surprised when people are surprised their ls7 lifters tick. We are talking about a high tolerance part consisting of several moving pieces and a good amount of steel that costs about the same as a pushrod.

Strokinit383

iTrader: (22)

I would not be alarmed if it was your average lifter tick. This is one specific lifter making an excessive amount of noise. Just trying to trace down the problem. I wish it were as easy as a rocker hitting the valve cover. Its definitely lower in the engine.