Byter

iTrader: (1)

I have had a loud ticking in the valvetrain for many months. I pulled the heads and replaced the lifters and the problem remained. I figured it was a bad rod bearing, so I left the car alone. Yesterday a mechanic friend said it was definitely a valvetrain ticking (quite loudly), so I've pulled the valve covers, let the engine run (oil everywhere), but noticed that the ticking frequency coincided with a valve opening and closing. Upon further inspection, I think I have narrowed down to an individual exhaust valve.

I've taken off the rocker arm and pulled out the pushrod. Visually all looks fine (I pulled another one just to compare). So I'm suspecting the lifter even though its brand new. My question is, can I run the engine with the rocker arm off and pushrod out, just to see if the ticking still happens OR will the lifter, floating free in the guide, cause a problem with the camshaft? Since its an exhaust valve, I guess I would have to disconnect the fuel injector and spark plug?

Thanks,
Tony

66deuce

iTrader: (1)

yeah,i would NOT do that.did you make sure the pre-load on the rocker in question was ok before you pulled it off?

Byter

iTrader: (1)

Yeah, it was a dumb idea. Also, I did check the preload and it was ok. This problem as been around for a while.

I do have another question. Let's assume that the rocker, pushrod, valve assembly are all ok. Also, assume that the lifter is in good working order. Is there anything with the camshaft itself that could cause a loud ticking, such as a bad lifter/lobe contact area? Any ideas?

Thanks...

DaleMX

iTrader: (4)

Did you make sure your exhaust bolts are tight? Double check anyway.

Could be a bent pushrod. Pull it out and roll it on a mirror.

Could be a lifter minus a few bearings. Remove the lifter and inspect it. You could even trade it with another cylinder and see if the noise moves. (I know, he looked at it)

Here's some other ideas:

Disconnect the sparkplug on that cylinder and see if the ticking goes away, if so then it's a rod bearing. Next do a leakdown test on that cylinder to see if your leaking. If you cant do a leakdown then a compression test might help.

Byter

iTrader: (1)

Thanks DaleMX. When this first started, I removed the headers, heads, and replaced the lifters, so:

1. The header bolts are tight.

2. Did the spark plug test but the ticking did not change.

3. Did not do a leakdown yet.

4. Pushrod is straight.

5. If you do the wooden stick to the ear listening test you can definitely pinpoint the noise to a location directly over an individual exhaust valve (i.e. place the plunger handle on the cylinder head wall above the rocker arm and listen).

6. I also used the shaft end of a hammer to push down on the pushrod end of the rocker arm to see if there was a change in the tone of the ticking. This test would determine if there was any "play" or lash problems with the valve geometry. Again, this did not prove anything.

I am beginning to suspect its something to do with the lifter even though its new. Perhaps its relationship with the cam or lifter guide is the problem.

You're right though in changing up the components to see if the ticking moves.

Thanks...

Gman2002Z06

What did you use as a measurement or basis for determining that your lifter preload was correct...

I had the ticking in my engine and cured it by going to adj. rockers...Preload after the cam install was not sufficient...

Peace...Gman

gollum

iTrader: (1)

Check lifter preload at heel of cam. OEM Rocker arms should tighten 3/4 - 1 1/2 turns past the point when pushrod cannot be spun between fingers. If less than 3/4 turn your pushrods are too short. Some people mistakenly purchase the short (7.35) pushrods when going to aftermarket higher lift cam. Stock length LS1 is 7.400.

Byter

iTrader: (1)

Thanks to everyone for their advice!

I pulled the head with the problem valve and found a big notch out of the cam lobe! Beats me what caused it since all of the old lifters seemed fine (i.e. no noticable uneven wearing on the rollers). However, I now need to swap the cam.

Thanks,
Tony

Gman2002Z06

You said you had this ticking for months...A possible cause of where that notch in the cam came from could very well be traced back to lack of preload...Hydraulic cams and Roller Lifters do not take kindly to having lash in the system...

The ramp areas of the two cams are quite different...With the Hyd. cam ramp design not being able to withstand the pounding that lash creates...

Peace...Gman

PREDATOR-Z

Here we go again talking about 3/4, 1/2 1/4 turns etc....Gollum, OEM rockers DO NOT take turns they take 22lbs/ft trq. That is it, no less, no more.
OEM rockers are NON ADJUSTABLE.
Only 2 ways to adjust lifter preload with aftermarket cams and OEM rockers
1- Custom length P-rods ( impossible as every valve would require a different length to achieve any consistant lifter preload measurement)
2- And this is the way it is usually done, is to shim the springs.

Also stock length p-rod is 7.38. 7.4 is aftermarket "stock length". the reason being is that aftermarket cams have a smaller centerline circle, the extra .02 is to compensate for that to a certain degree.

GrannySShifting

iTrader: (10)

What are you talking about? you can have different preload measurements, and too much will hang a valve. Preload is the amount from zero lash, until that 22 ft lb torque spec is reached. It can be changed with pushrod length, shimming the rocker pedalstool or going to adj rocker setup.