Just wanted to let others know what fixed my valve train noise. It was the push rods hitting the bottom of the pass through holes. When putting the engine together it looks like it would just clear the hole. Check your push rods right where they go through the holes. Full story:
Recently I built a forged 6.0L LQ4 setup for a turbo. I am running HS 1.8 rockers, PRC dual springs, hardened push rods and LS7 lifters set to around 80 thousands of preload. Rocker swipe is perfect as well. Ever since we fired it up for the first time it always had noisy valve train. I though it may have been the roller tip rockers so I swapped them out for the stock 1.7's. It was a little quieter but still too loud for me. I have heard engines louder than mine and quieter.
Things I did along the way:
-Clearanced the nubs on the valve covers to clear the rockers. No change.
-Replaced oil pick up tube o-ring and put BRP girdle on. Since was hearing the noise louder around the #5 and #7 cyl. No change.
-Put heaver weight oil in. 15w40 was the best. Help significantly. But noise still would come and go.
-Checked preload again before replacing lifters and found rub marks on the push rods. All but 2 of the 16 had wear marks on them.

It was easy to see the rub marks on the hardened push rods I have since they have a black coating. The stock one are shinny and not as easy to see. I checked all 3 of the LS eninges I have here and all 3 of them were hitting. 1 was stock and one had 1.85 rockers. The push rods hit on the lower part of the hole closest to the rocker mount holes.

I ended up taking a dremel with a metal rasp to the holes. I widened out the lower part of the holes to make sure they would not hit. I did this in car. I cover everything to preven shavings from going where I did not want them. I plugged the holes as best as I could and used a shop vac with a small hose taped into the main hose while cutting. I flushed the head and vacuumed out the lifter to make sure nothing got in there.

I wish I knew about this when putting the engine together because I would have just drilled the holes out bigger so I would not have worried about the shavings.

Hope this helps someone.

 

Glad you figured out your problem.

Not trying to be a dick, but when installing larger than stock rockers the push rod hole shouldve been checked for clearance. Not many people on here talk about checking the clearance there and hopefully your thread helps someone down the road.

Looks like a strong combo man, good luck with it.

 

Thanks. I did roll it over on the engine stand and all looked good. What about the stock engine that was hitting?

 

Damn, I mustve read right over that...

Is it completely stock? Not even a camshaft or anything?

 

Yep completely stock. It was really light rubbing compared to the built motor. But since they are the shinny push rods it is harder to see.

 

I did get to put some miles on the car this weekend since we had a quick break in the rain. It sounds great now. No more industiral sewing machine noise.

 

The stock pushrods hit because they flex very easily under pressure, especially at higher rpms.

 

im still a little confused on where its hitting exactly, are you talking about that tunnel that the pushrod goes through? you clearanced that?

 

ttt^^^ Would like to know if anyone else has heard of this?

 

picture explains a thousand words

 

Its easy to understand without a picture. The push rods goes through holes in the heads, as the push rod moves up and the rocker moves UP the fulcrum point of the push rod moves TOWARDS the valve. This causes the push rod to move closer to the hole in the head.

 

Still don't understand why they were hitting if this was an all stock setup and they hit with stock rockers as well. Were the valve lengths different?

 

now i understand since you explained it well, but like vettenuts said, how the heck can this happen on a stock setup? and if this is on a stock motor why is there only 1 thread like this since this engine was first made in 1997? i find that weird.

 

Honestly I think its overlooked, not many people would notice this. I have a feeling its common. Those holes should actually be slotted not round.

 

dang, i wish i looked at mine more closely before i put on the valve covers. i will try to look very closely at the old pushrods and see if i notice anything

 

I think you guys figured it out what hole in the head I was talking about. It is the tunnel that the pushrod goes through as stated above. I will try to get some pics from the engine that I have out of the car that has not been modified. This is a very easy thing to overlook. When I put my engine together is looked like it was going to be a little close but would still clear just fine. I am guessing once the lifters pump up it increases the height and angle of the pushrod and causes it to hit. If the holes in the head are a little small to begin with then it will be even worse. They are not exactly the best machined holes to start with. These engines make so many "normal" noises that we just write off, it makes it hard to know when we have a real problem. When the push rods were hitting it sounded like a noisy LS engine with the sewing machine noise. Now all I can hear is tolerable diesel like noise coming from the center of the plastic intake. No more ticking except for the roller tips making a little noise. I can not hear it in the car anymore either.

 

Here's a picture looking from the underside of the cylinder head.

Here's also some good information about pushrods from Terry Manton, one of the premier pushrod makers in all of racing:

QUOTE:
Column Theory

Because a pushrod is an eccentrically loaded column due to angularity load and arc motion within the engines atmosphere, whenever possible, it is most proper to use either a single taper or offset dual taper design pushrod. It is also very important to use the largest diameter pushrod that you can fit in the engine. This will help lessen deflection in the pushrod by putting the major diameter and mass where it is needed the most. The greater the angularity, the greater the arc motion. As the pushrod encounters this, the high load area on the tube moves closer to the energy source. The energy source being the lifter, as it travels up the ramp of the camshaft.

It makes it even more important to use these tapered designs when using large roller bearing diameters, increased valve lash, very high engine speeds, high rocker ratios, rapid valvetrain acceleration and high spring pressure. These tapered designs make it easier for the pushrod to do its job properly, and will enhance the performance of all the other valve train components, which will enable the engine to produce the maximum possible horsepower. The tapered designs and large diameters will also reduce valvetrain harmonics. Do not be over concerned about pushrod weight.

The difference between a stock 5/16 diameter pushrod in a small block Chevrolet and a 7/16 to 3/8 tapered pushrod, represents a difference of approximately 2.5% of effective weight. This is because the pushrod is on the slow moving side of the valvetrain. The effective increase in weight between the two pushrods may be small but provides a huge increase in valve train stability. Remember the valve side of this valvetrain is the critical side where any weight savings will make marked improvements. No matter what we change, valvetrain stability is the goal.

Important Special Instructions & Suggestions

It is very important to determine proper pushrod length. Improper pushrod length can cause a number of problems including excessive valve guide wear, lessened valve lift, valve stem side thrust, coil bind, improper valve to piston clearance and also rockerarm to retainer interference (in some cases lash caps can be used to help correct rockerarm to retainer clearance problems).

Check the radius of the lifter receiver cup and rocker arm cup/ball before ordering to help prevent mistakes. Improper ordering may result in parts failure. Watch for variations from stock radius in aftermarket lifters.

Make sure significant oil volume reaches the rockerarm end of the pushrod to help prevent galling due to excessive heat generation and lack of lubrication. To prevent interrupted oil flow to the pushrod, it is very common and almost always necessary to modify the lifter body so oil flows through it no matter where it’s positioned in the lifter bore (call for details). Oil restriction in the engine block is not normally recommended.

When possible, try to use larger diameter pushrods to spread out the load and lower the stress on the tube. This will help lessen pushrod deflection. Heavy wall tubing is a good idea also, to minimize compression. Many problems occur when a pushrod is inadequate for the application.

In high RPM applications tapered pushrods are a must for the serious racers. Tapered designs help to dampen harmonics in the valve train; extended valve spring life and increased usable RPM will usually be noticed.

Do not allow over clearancing for the pushrod. This may cause the pushrod to move around or deflect more than needed. Clearance of .010 at the closest point, wherever that may be during its complete cycle is sufficient. The cylinder head and engine block can often be utilized like a big guide plate and dampening device, which stabilizes the pushrod. Just make sure that there is no interference problems when turning the engine over on the engine stand.

Read that a couple times. As long as there is no interferance when the motor isn't running, i.e. turning it over by hand, then having the pushrods touch the cylinder head is actually helping to control pushrod flex. Instead of drilling out the cylinder head passages, go with stronger, larger diameter pushrods to decrease the flex.

Tapered pushrods should not be used in guide plate applications. Improper clearance and interference problems are sure to occur. Use only straight tube pushrods, specifically surface hardened for guide plate use in this application. Note: See series #2 and #4 for guide plate applications.

If you are using a tool steel rocker arm adjusting screw, it is almost always suggested that a tool steel pushrod tip be used at the rocker arm end. This will ensure proper compatibility.

per Terry Manton - Manton Racing Products


So as you can picture, the pushrod will flex during the loading stage on the cam lobe, which if the heads aren't clearanced enough, could cause the interferance and subsequent noise. This can happen on a box stock motor if the pushrod hole is off center a little bit or not as opened up as much as it should be, or if you have a weaker pushrod that is flexing more than normal.

 

i actually have a ticking noise in my car. its a stock 00 SS. i have good oil pressure and was thinking it was a lifter or rocker arm. i did pull a few pushrods and there is a small orn spot about a 1/4 inch long and about an 1/8 wide could it maybe be a slightly bent pushrod and i didnt catch it?

 

Holy crap! I would have never thought that the head is used as a guide plate!

 

Interesting read. Lots of great info. Thanks much for the post.
I am not really impressed with the crappy machined holes in head as a guide surface since they are all different sizes. None of the old small or big block chevy engines had "guide surface" clearance issues.
Bottom line is that even a stock engine may need to be clearanced to make your valve train noise go away. Mine was the most noisy at idle and up to around 3k RPM and then it was either drowned out by exhaust or maybe the lifters changed the height of the push rod as the oil pressure changed.
I will get some pics up as soon as I get a day off from work.