LT1 Hotcam Install , Valve clatter
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 16
Likes: 2
LT1 Hotcam Install , Valve clatter
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 ?
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
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.
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.
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 16
Likes: 2
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.
Melting Slicks
Joined: Jun 2004
Posts: 3,253
Likes: 2
From: Castro Valley CA
You might want to post here as well:
http://web.camaross.com/forums/forumdisplay.php?f=9
A lot of very experienced LTX engine builders reside there, good luck and post the results; I was thinking of doing the Hotcam upgrade myself.
http://web.camaross.com/forums/forumdisplay.php?f=9
A lot of very experienced LTX engine builders reside there, good luck and post the results; I was thinking of doing the Hotcam upgrade myself.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
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.
Le Mans Master
Joined: Aug 2002
Posts: 6,080
Likes: 3
From: Clearwater FL
St. Jude Donor '06
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
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.
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.
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 16
Likes: 2
[QUOTE=
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.[/QUOTE]
Sorry to hear your scuffed the cam, other than the scuffed cam how did detemrine lifter was bad ? Was it visibly damaged or other ?
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.[/QUOTE]
Sorry to hear your scuffed the cam, other than the scuffed cam how did detemrine lifter was bad ? Was it visibly damaged or other ?
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 16
Likes: 2
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.
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.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
It may be only a mis-statement on your part, but you repeatedly referred to "valve lash" and "lash", but I suspect what you actually mean is "lifter pre-load", since "lash" is for mechanical cams.
Anyway, just to eliminate the adjustment procedure as the possible cause, how about posting the exact, step-by-step procedure you followed.
I've never checked into this so I'm asking: Are the lengths of the LT1 and LT4 pushrods the same?
Could the mark you found on the rocker arm be caused by interference with the vavle spring retainer? Is there any sign on contact on the retainer?
I much prefer the adjustable lifter preload method as opposed to the method where the nuts are cranked down.
Jake
Anyway, just to eliminate the adjustment procedure as the possible cause, how about posting the exact, step-by-step procedure you followed.
I've never checked into this so I'm asking: Are the lengths of the LT1 and LT4 pushrods the same?
Could the mark you found on the rocker arm be caused by interference with the vavle spring retainer? Is there any sign on contact on the retainer?
I much prefer the adjustable lifter preload method as opposed to the method where the nuts are cranked down.
Jake
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
With hydraulic lifters, you must still find zero lash point before you can adjust preload.
It may be only a mis-statement on your part, but you repeatedly referred to "valve lash" and "lash", but I suspect what you actually mean is "lifter pre-load", since "lash" is for mechanical cams.
Anyway, just to eliminate the adjustment procedure as the possible cause, how about posting the exact, step-by-step procedure you followed.
I've never checked into this so I'm asking: Are the lengths of the LT1 and LT4 pushrods the same?
Could the mark you found on the rocker arm be caused by interference with the vavle spring retainer? Is there any sign on contact on the retainer?
I much prefer the adjustable lifter preload method as opposed to the method where the nuts are cranked down.
Jake
Anyway, just to eliminate the adjustment procedure as the possible cause, how about posting the exact, step-by-step procedure you followed.
I've never checked into this so I'm asking: Are the lengths of the LT1 and LT4 pushrods the same?
Could the mark you found on the rocker arm be caused by interference with the vavle spring retainer? Is there any sign on contact on the retainer?
I much prefer the adjustable lifter preload method as opposed to the method where the nuts are cranked down.
Jake
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Jake
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 16
Likes: 2
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. ?
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. ?
Last edited by Tuff96LT1; Nov 10, 2008 at 04:46 PM.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
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.
Jake
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.
Jake
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 16
Likes: 2
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 ?
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 ?
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
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."
"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."
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
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."
"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."
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.
Jake