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OK, folks help me out here. I just installed a new GMPP Lt4 Hot cam kit in my 96 LT1. All was well. I took my time and installed the new GMPP LT4 hotcam, kit came with lifters and lifter tray, and 1.6 roller rockers. I used my original push rods, all checked ok installed a new LT4 HD timing chain set and new Accel Opti. Had the pcm tuned by PCM4LESS. Went together fine, cranked and ran/runs great . After a couple of hundred miles I now get a LOUD clatter from what seems to be cyclinder #8 around 2000 rpm. I warmed up the engine, pulled the valve covers to readjust lash hot and running. Only odd thing I noticed was last valve at back of passenger side was getting 10 times as much oil to the top as compared to any other valve. Oil spraying everywhere. Valve lash seemed ok, and I adjusted to zero plus half a turn. Capped it all up, engine cranks fine, runs fine and is quiet at idle ( normal ticks and clicks) but at 2000 or rpm, clatter is very loud. Quiets down at higher rpms and is quiet at idle. What gives ? Any suggestions ?
Well my first guess was going to be that your rockers had worked themselves loose. Normally though you will notice that at idle.
You didn't mention your springs? I thought they came with the hot cam kit. If you did springs and forgot to mention them, I don't know what to tell you. If you didn't do springs, I would say to start there. Stock LT1 springs are marginal for 1.5 rockers. With 1.6's they are dangerously close to coil bind.
It could be that above idle they are so weak that the inertia is "throwing" them into coil bind. It could also be that above idle the springs can't close the valves quick enough and what you're hearing is the slop in the valvetrain caused by the spring not keeping the rocker firm against the pushrod. Worst case it could be valve float and you're hearing the pistons slapping the valves.
I would hope for the first two options. Again if you did do springs, you can disregard these scenarios.
Yes , springs are new, came with the kit. Odd it does not clatter cold, but as soon as it warms even a little the passenger side really clatters loud ( seems like cyl #8). Each bank has one lifter ( pushrod & rocker ) that really pumps a lot of oil, all others look normal. I am thinking the lifter(s) is bad, but think it is odd since they are also new.
If memory serves the rear cylinders seem to get oil more quickly than the fronts at idle. As soon as you get it some RPM's though they all should flow fairly evenly, as far as I can remember. It's been a lot of years since I've had the covers off of mine.
I have a ditto to the noise. Stock LT4 here. The noise started appearing at about 3000 rpm and went away at 4000. Gradually it started getting there at 2500, then 2000. I was hoping that it was an exhaust leak, as the sounds can be similar. Changed the gaskets and I was only half right, the stock gaskets were toast. But, I finally went in for a lifter change and I was right. Unfortunately, the bum lifter scuffed the cam. Hoefully the hotcam in my possesion will be going in next month.
I would check the lifter. The only cost you'll be out is to replace the intake gaskets if you do it yourself. At least you'll know for sure.
OK, covers off.
I cranked engine cold and the ticking seemed to come from #8 exhaust. Also it was pumping oil all the way back to the MidEast. All the others had the normal dribble. So I proceeded to remove intake etc.
Once in I took off #8 cylinder rocker, pushrod and lifter.
I did notice a sharp burr in the edge of the rocker in between the cup and rocker where the pushrod sits. It wiped off easily and no other issues seem to be with rocker. checked Pushrod, is not bent nor damaged. Checked Lifter and it too looks normal, I cannot see anything wrong with it.
I am going to replace the pair of lifters in #8 anyway as at least the only sign (REALLY HEAVY OIL SPRAY) came from that lifter as compared to all else.
Does anyone think I may be on the right track ?
Also, can I replace the rocker studs and lock nuts with LT4 versions with the GMPP Hotcam LT1 Kit 1.6 rockers and simply just torque them down ? Seems that would be an easier valve adjustment.
LASH for a hydraulic cam
That is why the instructions for the LT4 Hotcam kit call for (0) ZERO lash plus 1/2 to 1 turn after. I used both the not running method of #1 TDC, adjust LASH to zero and turn crank 1/4 turn to adjust according to firing order there after as well as the running method of loosening to hear clack and than tighten until quiet plus 1/2 turn.
What about the 1 lifter pumping the heck out of oil. ? Is that a sign of a defective one. ?
I prefer to use "Zero Pre-Load" just to avoid any confusion. But as long as you didn't actually set LASH with a feeler gauge, then we're on the same page.
Although you didn't say specifically, but did you make sure you established the lifter preload while the lifter was on the base circle of the camshaft lobe? That's an error that many make; setting the preload while the lifter is on the ramp of the cam lobe.
Any sign of rocker/retainer contact? How about the underside of the valve cover, any sign of valvetrain contact there?
If the lifter is collasped, it should be very easy to depress the plunger by pushing on the pushrod. Not sure why there's so much oil spraying there; I'll have to chew on that one a while.
Lifter Pre-Load was set while at base of cam lobe.
No signs of any contact to the retainer or the valve cover. Also note the noise was not there the 1st 100 miles. Lifter is not collapsed and I cannot push the plunger by hand at all.
When inserting the lifters , which way do the oil holes face ?
I didn't miss a thing. I am well aware of what lash is. You must adjust the rocker on a hydraulic motor to zero lash prior to turning further to set the preload. The 96 FSM says:
"ZERO LASH can be felt by moving the valve pushrod up and down between your thumb and forefinger until there is no more movement.
When all free play is gone, tighten the valve rocker nut 1 additional turn."
There's a bit more to it that just that. You must first ensure that the lifter is riding on the base circle of the camshaft lobe. If it's anywhere else you won't have the correct position to establish ZERO pre-load/lash.
But I'm not going to spend any more of my time debateing this with you. I prefer to spend my efforts trying to help the original poster.