Casey_SS

One of my stock lifters recently developed a tick that would come right back after adding a half - 3/4 turn of preload, so I just threw in a set of the Comp OE replacements (850-16) over the weekend. I set them to a half-turn past 0 lash using the IC/EO method (thanks Shoebox!), let the intake RTV cure for 24 hours, fired it up and wow....they made quite a racket! Tried 3/4 turn, which was better but several were still clacking away, so finally tried a full turn, which was much better. Passenger side sounds great but still some minor ticking on the driver's side even after another 1/4 turn on a few of the louder ones. Why would these lifters need so much preload?? Everything I've read, including Comp's documentation says half a turn is plenty...
If it helps any, I'm running the stock cam (130K) Comp hardened pushrods (stock length), LT4 springs, and Comp Magnum rockers (not PRO Magnums, just the cheapie roller tip ones), and stock 3/8" studs.

I talked to Comp this morning and they said .030 to .060 (half turn - 1 full turn on 3/8 stud) is the spec and I should be fine but didn't really have any other insights.

Anyone else need this much preload on a stock or stock replacement lifter? Going road racing in less than 2 weeks and I want to get these as close to perfect as I can...

seawolf06

Are you sure it's the lifters that are ticking? With a loose rocker it will tick as well.

Did you try to set them with the engine running? To me, this is the most accurate way to do it.

Casey_SS

Unfortunately, I can't really set these with the motor running for 2 reasons:
1. These rockers use a stock-type lock nut located inside the body of the rocker arm - putting a socket in there while it's running causes the rocker to bind against the socket / stud. I'll never run a set of rockers without PermaLocs again, but for now these are what I'm stuck with.
2. I'm running a Racetronix fuel pump with the wiring harness, which gets power directly from the alternator. Unless I did some rewiring to temporarily run it off the battery, the alternator has to be in place = PITA to set pass. side with motor running.

I kinda look at the ticking to be a product of general slack in the valvetrain rather than one component versus the other. If a lifter won't pump up properly it creates slack = ticking. If a rocker isn't tightened down enough it creates slack = ticking. With the new lifters I can reasonably rule out lifters not pumping up as the culprit and with one full turn of preload it's hard to argue that the rockers aren't tightened down enough.

One full turn + or - 1/4 is the factory spec and I'm ok with that, I'm just wondering if anyone else has had to use this much preload on these particular lifters or on the stockers to quiet them down. Everything I've read recommends half a turn....Even at one full turn, these are still loud enough to occasionally **** off the knock sensor.

SStrokerAce

You gotta let the lifters fill with oil first. I would back them off to close to zero preload, run the motor to get the oil pressure up in them and then you can reset them. They don't need more than a 1/2 turn at all.

Bret

Casey_SS

Thanks Bret...I was hoping you'd chime in on this one

I thought about the oil pressure aspect as well and here's what I did about it...feel free to troubleshoot my logic:
- cleaned lifters with mineral spirits, dried 'em and soaked overnight in clean oil
- pulled them one at a time out of the oil and straight into the lifter bores
- set lash to half a turn and let intake RTV cure for 24 hours
- started it, let it warm all the way up and revved it to ~3k a few times to get some oil pressure in them
- valvetrain was very "clacky" sounding and was getting lots of knock retard when revving it
- reset to 3/4 turn using same IC/EO method, poured fresh oil over rockers - better but same issues as above
- reset to full turn doing everything the same and it sounds "stockishly" quiet now but still getting intermittent knock retard after 100 or so miles. KR has never been an issue with this car in the past. I've had the rockers / springs installed for well over a year with no KR issues. Only real change is the lifters - I started getting some KR when my stock lifter began ticking and I can't seem to get these new ones quiet enough to make it go away.

Thoughts / recommendations? Not sure where to go from here...gonna try some race gas this weekend to rule out any real knock but I'm not expecting any change from that. Pretty sure it's the valvetrain pissing off the sensor. BTW, it's an LT4 KM, OBDII tune by Ion with his standard KS desensitization.

SStrokerAce

Check to make sure you adjusted the rockers when they were on the base circle.

seawolf06

That's what I was thinking as well. Which is why I suggested the engine running method. I'm not sure how much you like that one, Bret, but it's easiest for me.

For the alternator, just remove it to get the valve cover off and replace it without the valve cover on. Then you can run it as long as you need.

maybe2fast

I just finished my H/C build and set my pro mags to half turn as Comps instructions told me too. I am getting some small ticking from under both valve covers but is not a huge noise. I am thinking about readjusting them now because of the oil pressure is now in them. car runs great though. just can hear the noise and want it to be right.

Casey_SS

Bret - I used the IC/EO method on each cylinder, turning the engine over by hand. When I set them to half a turn, I still had the intake off and could watch the actual lifters themselves. I'm extremely confident the rockers were on the base circle of the cam each time. Any other thoughts?

Seawolf - I hear ya man and completely agree it's much easier to do with the engine running, just not on this type of rocker arm due to the binding issues I mentioned above.

Sounds like I can safely interpret all this to imply that nobody else has really needed this much preload to appease a desensitized knock sensor. Oh well... I'll keep tinkering with it and reply with any useful discoveries once I get things sorted out. Maybe it's real knock after all and just one hell of a coincidence....

Thanks guys.

gitsum

I have the exact same lifters, and have re-adjusted them several times, but they still make noise. Maybe these lifters just are just loud? If pushrods are too long or short can they make noise?

firebirdStud

mine are loud too, wether its at 3/4 turn or 1/8 turn. So, I put them at 1/8 turn for the best performance, and now Im lookin for some corvette composite valve covers to hush the valvetrain up a bit.

Casey_SS

Are you guys seeing any knock retard?

JAKEJR

I'm new here; spent most of my time on the CorvetteForum, but this thread caught my attention.

Since we're talking lifter preload adjustment, has anyone seen TPIS' LT1 booklet where they're now recommending 2/3 FULL TURNS from Zero lash?

I've been screwing on these suckas for over forty years and have NEVER seen a recommended preload adjustment anywhere close to that.

Jake

firebirdStud

No knock retard now... but I got greedy and set my timing ahead 5 degrees... got hella retard there. So, I backed it off, still pulled 438rwhp, and no knock retard. So, I guess I need to just be happy.

gitsum

I dont have knock retard either.