Mangled03gmc

iTrader: (95)

That is why I mentioned it because he never said he ran the **** out of it. Yes valve float can cause issues. I don't think that is the issue, but nothing is going to be known untill a visual inspection is done..

Ferocity02

iTrader: (59)

I measured the preload on a five of the lifters on the driver side using a dial indicator, and ended up swapping in 7.350" pushrods on two of them to get the preload above 0.070, including the exhaust valve on 7. It's amazing how much the preload can vary from valve to valve, but I guess it makes sense, there's many many factors involved

Anyways, there was no noticeable change in the tapping sound, if anything it's slightly louder but not to the point of saying I made it worse, probably just paranoia.

Gonna check the rest of the preloads tomorrow, but I think it's safe to say it's not a lifter preload issue.

06murder

Did you use aftermarket rockers?

Ferocity02

iTrader: (59)

Stock rockers with Comp trunion upgrade. They are all in perfect shape.

An update on the sound. I originally posted that it taps cold or warm. Actually, on a cold start it will not tap at all, then it takes 20-30 seconds before the tapping begins.

Ferocity02

iTrader: (59)

Little update... I checked the preload on each lifter with a dial indicator and ended up swapping in 7.350's on 5 valves to get between 0.075 and 0.100 preload, all exhaust valves strangely, some ended up around 0.095. Noise was the same. I may put them all back to 7.325.

Then I ran the motor with the rockers/pushrods off of cylinder 5 then 7 so these lifters weren't being used. With the rockers/pushrods removed from cylinder 5, the tapping was significantly reduced or gone. I did it twice to confirm. With them off 7 the tapping was still present. The lifters appear to be good; they compress and bleed down okay when the rocker is tightened, and pop back up with the rocker removed.

THEN, as a last ditch effort I switched back from Rotella 5W-40 to Mobil 1 10W-30 and the noise is significantly reduced, by 50-70% I'd say. Still a little early to tell, but the thinner oil has helped greatly. There is still a tapping sound, but it's more like the normal sewing machine than the metallic sound I heard before.

Anyone have thoughts to why a thinner oil would help? With the 160* thermostat and e-fan settings it cruises at 173F and idles around 185F. Hot idle oil pressure is now about 37psi, with the 5W-40 it was about 42psi.

Either way, sounds like the lifters need to be changed. And I may go with a higher pressure oil pump.

Chevy_freak

Actually, I was going to suggest that.

I tried switching my lq4 over to rotella t6 5-40 and it did the same thing, and its all stock. Changed the oil after a couple hundred miles and it all went away again. You'd think a thicker oil would quiet it down, but I've noticed the exact opposite.


Id actually go to 5-30 and see if it helps more, since youre actually going to run the oil cooler than designed with a 160 t-stat. IIRC oil temp is usually around 250* with a motor running at 210*. And since preety much all factory motors run around 200-210, the oils are designed to work there. I know my yukon is noisier in the winter when the oil never really gets hot.

Or, Ive just done way to much reading on bobistheoilguy.com and my mind has self-destructed.

Ferocity02

iTrader: (59)

Thanks for the thoughts. There is still something wrong with one of those lifters IMO, so I went ahead and ordered a new set of LS7 to throw in. I will also be switching to PAC 1218 springs since the dual springs I'm using now are way overkill for my cam. Hopefully this will make the life of the lifters a little easier. Also putting in a new timing set and a Melling high volume oil pump while I'm at it.

I may also try the stock stat like you suggested. I was thinking that having the engine run 20* cooler wouldn't affect the oil viscosity too much. But, the tapping noise still happens as the engine is warming up, so I'm not sure how much the stat has to do with it.

Velocity1

iTrader: (3)

Based on the run without the push rod/rocker arm during your test of suspect cylinders 5 and 7, IMHO, it sounds like you're chasing a weak lifter in cylinder 5 that isn't up to the task. All of the other variables you mention, springs, oil temp., pre-load, viscosity, harsher cam lobe profile all exacerbate the weakness or improve this lifter's performance. If none of the other cylinders are making noise, I'd say your setup is good. Often it's believed that more spring pressure is better, regardless of cam that is being installed. Not necessarily true. Hugh seat and open spring pressures can result in unexplained valve train noises. Best bet is to run springs that have been spec'd. by the cam designer for the specific cam.

I'm betting a fresh set of lifters and springs matched to the cam's requirements takes care of the problem. In most cases it does. My '00 5.3l has had a light tick to it when cold, whether winter or summer since 98k. Other than the tick being a little more pronounced now, the weak lifter still pumps up after about 45-60 seconds of running and is dead silent until the next cold restart at 140K.

I'm getting ready to "freshen up" my top end with probably a TSP 220, valve job, seals, springs, lifters, trays, push rods. My oil pressure at 600 rpm is 45-50 psi. It's 60-65 psi at 5500 rpm. Motor is bone stock.

While I'm confident, there's no guarantee I'll have a quiet valve train.

Wear variation alone between lifter bore diameters can often be the cause.

I think because your noise never completely goes away, and you've isolated cylinder #5 as the offender, I'd pull it apart, change the lifters and springs and see if the sound isn't gone.