Valvetrain problems! Clack Clack

[molitor]

Ever since i bought this truck, its always had a little ticking to it...Not anymore.
Now it clacks, and loud too! Sounds like on single cylinder's exhaust valve. I say that because you can hear it ringing all the way from the primary tubes to the tail pipes. I'm going to pull the valve covers tommorow night to see whats going on. Hopefully nothing is broken or bent. I'm afraid of what i may find. Oh yeah, i recently installed my 1.75:1 rockers for the second time. Hopefully one of them is the problem and nothing catastrophic has occured.

i also will be driving it to work tommorow morning. call me crazy but i just drove 2 hrs form huntsville up here. no power but otherwise running fine.

[molitor]

Ok! so last night, i pulled the shaft rockers off and inspected them all, boxed them back up and reinstalled all my factory rockers. It doesn't look like i have any bent valves or anything in the heads for that matter. I'm not very sure at all what the problem could be but i'll get to run a compression test tonight. Hopefully i don't have a spun bearing or a bent rod. I'm still waiting, as i have been for four months, to get my 6.0L back from the machine shop. If i had gotten it months ago like i should have, i could just do the swap this weekend. But no...

On another note, i did find that i had the pcv hose disconnected and have probably been running with a vacum leak for quite a while.

[molitor]

Ran a compression test on all eight cylinders and came up with this
Cyl. No. / Pres. (psi)
1 / 150
2 / 168 <<\\
3 / 150 >>These are adjacent on pass. front of engine 28psi diff.
4 / 140 <<//
5 / 150
6 / 160
7 / 150
8 / 150

So, number 2 and number 4 concern me...
High compression is rarely a bad thing but a 28psi variation between two cylinders next to eachother is wierd. Not sure whats going on here...I think it is a bad camshaft based upon the reading though.

one to phase 2!
overhead---I got out my dial indicator and decide to check the travel of the rockers. Unfortunately with the heads on, i was unable to switch to a solid lifter which will give you the most accurate readings. But if you can keep the crank moving and watch your dial and know what your are reading, you can get within .010'' of your measurement.

i checked the exhaust on the no. 2 cylinder and then the intake valve.
The exhaust checked out ok, in 120k miles it has about .010'' wear(if any). The intake valve, however, read consistently, (.355'') and this is measuring the travel of the rocker tip, so max lift. and max lift for this cam is spec'd at .457'', so thats .100'' wear!

i'm gonna keep checkin but so far this cam looks pretty bad.

[molitor]

i do have an ls1 cam though, here is how they compare...

191/190 457/466 114lsa <<LR4 camshaft 4.8L
196/207 467/479 116lsa <<ls1/lq4 camshaft (base 5.7L and 6.0L)

i think that would a pleasant deviation from the stock cam. just putting a new stock cam would make a difference for sure, but adding 10dg and about .020'' lift, that will make much more power!

[molitor]

here is good solid info on valvetrain problems and camshaft failures

Cam lobe failure analyses. - LS1TECH

[molitor]

So after all the compression testing, my lower end is all in good shape and all my piston rings appear to be in good shape.

I do have vacum fluctuations that suggest problems with the opening and closing of my intake valves. I followed this route and went to the noisier side of the engine. I took off the valve cover and exposed the rocker arms. I then removed each of the intake rockers one at a time. 2,4, and 6 made no change when removed other than the usual popping. Number 8 however completely eleminated my clacking and ticking! I then removed the exhaust valve and it got even quieter.

I don't have any way to tell the condition of the rollers on the lifters otherwise I would just swap cams if I knew the lifters were ok. As it stands, I might as well swap camshaft, heads, and lifters all at once to be safe.

Hopefully tommorow the machine shop will have some good news and i can just wait it out till my new engine is finished, bring it home, assemble it, and then swap.

[molitor]

OK, well the machine shop has started working on my engine after 4 months of waiting... I've decided to just drive my truck around with two collapsed lifters and hope it doesn't do something stupid before the other engine is finished. Thats all for now...