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Help! LT1 Hotcam Install , Valve clatter

tuff96lt1

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Feb 15, 2008
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1996 Red Coupe
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 ?
 

Hib Halverson

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I've been thinking about this one on and off today.

Have you looked at the valve springs for #8 to see if there's a broken one?

Also, why are you setting the valves hot? With a hyd. lifter engine it's easier, and certainly less messy, to set the 1/4-1/2 turn preload, with the engine cold and rotating the engine by hand. Set the intake just as the exhaust starts to open. Set the exhaust just as the intake begins to close.

The extra oil spray has me thinking, if you don't find a bad spring, the valve lifter where the spray and noise are coming from is bad.
 

tuff96lt1

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Feb 15, 2008
Messages
15
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1996 Red Coupe
Havn't checked valve spring yet, will do so tomorrow. Hope it is not a bad lifter. What a pain that will be. If it were a bad spring, wouldn't it make noise all the time. ?

As for hot valve set, seems that was when noise was worst.
 

tuff96lt1

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Messages
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1996 Red Coupe
Also by the way , the springs came with the kit and are new.
 

tuff96lt1

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Feb 15, 2008
Messages
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All springs are good. No broken ones. Seems like lockdown nut is awefull close to top edge of rocker. Coukd some interference be cause for noise here ? Also can a rocker seat be installed upside down, the part that sits on stud ?
 

Toms007

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yes the seat needs to have the flat part up for the locking nut to sit on.
 

tuff96lt1

Member
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Feb 15, 2008
Messages
15
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SC
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1996 Red Coupe
OK, covers off.
I cranked engine cold and the ticking seem to come from #8 exhaust. Also it was pumping oil back to the Mid East. 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 inbetween the cup and rocker where the pushrod sits. I wiped off easily and no other issues 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.

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.
 

JAKE

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313
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1996 388 LT1
So what's the latest?

Jake
 

tuff96lt1

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Feb 15, 2008
Messages
15
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SC
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1996 Red Coupe
OK folks here is the outcome.

1st, thanks to everyone for your input. It was most valuable.

Yep, It was the lifter.

I installed 2 new GMPP roller lifters in cylinder #8.
I certainly love not draining the coolant to replace these on the LT1.

Put it all back together. And TADA,

No more pumping oil from here to eternity on any of the rockers.
Just a nice steady flow at idle.
And most important the loud clattering at 2k plus is now gone.

Of course now I am now gun shy with all the noise that the roller rockers do make
thinking that any noise must be unacceptable, but I am sure I will get used to it.
At least the one loud clattering is gone, (FOR NOW, fingers crossed X)

Lesson learned, If I have to do this again (gut feel) I will NEVER use GMPP lifters again.
Probably not GMPP Roller Rockers either. Hotcam is great.

As for performance, I have now installed the GMPP Hotcam kit, bypassed Throttle coolant,
moved IAC sensor, have an SLP tri K&N air breather and SLP exhaust as well as a
PCM4LESS PCM tune. Car sounds great and runs very strong. Easy to get used to and hard to
remember stock power until I compared side by side with a friends stock C4 and the differance
is UNBELIEVABLE !

By the way, those who say a OBD2 car can run stock tune with Hotcam install are nuts, yea it will run
but like crap and throw all kinds of codes. PCM4LESS tune is a must and solves 100% of the running
problems caused by PCM.

Next up, 3.54 or 3.73 rear gears.
 

tuff96lt1

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Feb 15, 2008
Messages
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1996 Red Coupe
Part 2,

After another 100 miles. I romped down on it and the ticking came back. I could tell though it was from a differant lifter. Decided what the heck and drove around a little and romped on her again. TADA the ticking went away. Seems this time for good as more hard driving couldn't get it to return again. My guess , must be a lifter guide or spider plate getting positioned.

Next issue is a knock around 2000 rpm upward to about 3500.
Think either gas or may have to tune back timing on PCM.

Will let all know soon.
 

tuff96lt1

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Feb 15, 2008
Messages
15
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SC
Corvette
1996 Red Coupe
Definately NOT gas or PCM tune.
Definately mechanical noise.
Seems to be coming from same problem cyclinder #8.
No noise when cold, only once warms up and only starts around 1500 and up.
I disconnected electrical to injector #8 and noise can then be heard ay idle.

Any ideas ?
 

JAKE

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Messages
313
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1996 388 LT1
So, you're saying that changing the lifters on #8 cured the heay oil flow and that things returned to normal for a while but NOW the tapping noise has returned, right? If so, three things:

First, post the detailed step by step method you used to establish the lifter preload. I mean DETAILED because "the Devil's in the details".

Second, did you change valve springs? If so, did you set the seat pressure with shims after establishing the installed height/seat pressure for each spring?

Third, also, run your fingers around all the valve springs to feel for any indication that one has broken. Some breaks are really difficult to see, so look closely with a BRIGHT light and feel gingerly for any break.

Sometimes if new springs aren't PRE-STRESSED in a vice before being installed on the engine, one or more will break OR lose seat pressure once the engine is running. It's probably more prevelant in racing springs than in street springs, but it can happen in both.

The procedure is to clamp each spring in a bench-vise, one at a time. Crank the vise down until the spring is in coil-bind. Let it sit that way for a couple of minutes, then remove and move onto the next spring. This pre-stresses the springs causing them to maintain seat pressure much more accurately. I learned this trick from Air Flow Research many, many years ago (more than 30 years) and I use it religiously when installing new springs. It's especially beneficial on racing springs that have up to 300# of seat pressure. It eliminated spring breakage on BBs I use to build.

Try using a rubber hose with one end stuck in your ear and use the other end to probe around the area with the engine idling to try to pin-point exactly where the sound is coming from.

Hope some of this helps.

Keep us posted.

Jake
 

tuff96lt1

Member
Joined
Feb 15, 2008
Messages
15
Location
SC
Corvette
1996 Red Coupe
So, you're saying that changing the lifters on #8 cured the heay oil flow and that things returned to normal for a while but NOW the tapping noise has returned, right? If so, three things:

Not a Tap, the tapping is gone and now there is knock.
VERY VERY differant sound than the clattering I was getting before.
The Knock IS NOT there at idle.
The Knock IS NOT there cold.
The Knock only occurs once you get a warmed up engine and around 1500 rpm and up. Seems to come from same area as the lifter problem.

First, post the detailed step by step method you used to establish the lifter preload. I mean DETAILED because "the Devil's in the details".

Adjusted valves both engine off and engine running.
Last time was while running, Loosened until I heard a clacking, tightened until that just went away and then tightened an additional 1/2 turn. Locked it down.

Second, did you change valve springs? If so, did you set the seat pressure with shims after establishing the installed height/seat pressure for each spring?

I did change the springs, new ones came with hot cam kit.
Kit came with springs, new seats, cap and locks.

Third, also, run your fingers around all the valve springs to feel for any indication that one has broken. Some breaks are really difficult to see, so look closely with a BRIGHT light and feel gingerly for any break.

Best I could tell springs are ok. I took out spark plugs and they look perfect. I will probably go ahead an remove springs just to double check.

Sometimes if new springs aren't PRE-STRESSED in a vice before being installed on the engine, one or more will break OR lose seat pressure once the engine is running. It's probably more prevelant in racing springs than in street springs, but it can happen in both.

The procedure is to clamp each spring in a bench-vise, one at a time. Crank the vise down until the spring is in coil-bind. Let it sit that way for a couple of minutes, then remove and move onto the next spring. This pre-stresses the springs causing them to maintain seat pressure much more accurately. I learned this trick from Air Flow Research many, many years ago (more than 30 years) and I use it religiously when installing new springs. It's especially beneficial on racing springs that have up to 300# of seat pressure. It eliminated spring breakage on BBs I use to build.

Try using a rubber hose with one end stuck in your ear and use the other end to probe around the area with the engine idling to try to pin-point exactly where the sound is coming from.

I have a shop stetho and at idle cannot hear anything abnormal.
However IF I disconnect the fuel injector while things are running, I can then hear the knock. PLug the injector back in and the knock goes away until revved to 1500 rpm or higher.

Hope some of this helps.

Keep us posted.

Jake


What do you think about the fuel injector being pulled and hearing the knock at idle ?
 

JAKE

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1996 388 LT1
So we're talking a KNOCK, right? Not tapping, right?

How's your oil pressure and temp look?

Does the noise seem to be dependent on the temps of the coolant and/or oil?

What weight oil are you running?

Am I correct that all this began after the installation of the Hot Cam, that everything was normal before?

Jake
 

tuff96lt1

Member
Joined
Feb 15, 2008
Messages
15
Location
SC
Corvette
1996 Red Coupe
So we're talking a KNOCK, right? Not tapping, right?

How's your oil pressure and temp look?

Does the noise seem to be dependent on the temps of the coolant and/or oil?

What weight oil are you running?

Am I correct that all this began after the installation of the Hot Cam, that everything was normal before?

Jake


Oil pressure is normal. Temps of both coolant and oil are now lower than previous since I installed 160 thermostat. Oil weight is 5w30 Mobile 1, and yes this started after Hotcam install. Though it ran fine for a a few miles.
Had a new lifter go bad so I went on my gut and changed that and it solved the particuler problem with the lifter. Now I think the lifter problem may have done something to a rocker, so I am going on my gut here as well and going to move them around to see if the noise moves.
 

JAKE

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1996 388 LT1
When everything is normal and some work or some change is made to the engine, then a problem arises, it's almost always caused by the change that was made. Same thing with computers.

So I'd first re-check everything; doing the most obvious and easiest things first, like proper plug wire routing, correct injector wire plug in locations, etc.

I don't know of any quick fix, assuming you're not getting any error codes. It's going to be a process of elimination.

If you know anyone nearby who's up on engine, have him/her have a look see. Sometimes a NEW pair of eyes/ears can detect something you've missed.

I remember a friend called me over once to see why he couldn't degree in his new cam. Turned out he'd installed the dial indicator on he exhaust lobe instead of the intake. No wonder the numbers didn't check out.

Just my thoughts.

Jake
 

JAKE

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1996 388 LT1
Did you ever track down the cause of your problem?

Jake
 

tuff96lt1

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Feb 15, 2008
Messages
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1996 Red Coupe
OK , folks here is the result.

*&#%$ SPUN Bearing. After all the fus and how it ran so well after the hotcam install, I finally got around to doing what I did not want to do ( I did not want to confirm my worst fears ) anyway, Drained the oil, NICE metallic looking color, removed oil filter and cut it open and found every pleat filled with metal particles. So now after ALL the work, I will be starting over for the winter.
 

JAKE

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KEMPNER, TX
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1996 388 LT1
Sorry for your loss; I know the feeling.

Surprisingly, your loss isn't uncommon. Over the past few years, I come across several posts on other Forums put up by guys who have experienced the exact same thing.

They changed the cam and ended up with a spun bearing. A lot of the responses say things like "well, the two things aren't connected" or "I don't see how just changing the cam can cause a rod bearing to spin", but this seems to happen so often that there MUST BE a connection. Guy changes the cam and spins a bearing.

I haven't come across a mag article where someone, somewhere has tried to track down the connection, but I believe there has to be one, somewhere.

Anyone have an update on that???

Anyway, You can change the bearings with the engine still in the car. This'll work if the crank isn't scored too badly.

I've done it successfully before and even used the show-string method to polish away slight roughness on the journal. I then used plasti-gauge to see if the clearance was still within spec. All that with the engine in the car and me on my back under it.

Of course, if you hadn't planned on using the car over the winter, then you may opt to pull the engine and tear it down for a full going-over by a reputable machine shop. If you go that route, I recommend you use a shop that works on racing engines as its primary business. Not a shop that primarily does dealership, warranty work. A racing shop will hold the tolerances/clearances at lot closer.

Jake
 

JAKE

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Messages
313
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KEMPNER, TX
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1996 388 LT1
I hate to see anyone have a failure and NOT know what caused it, so I just thought of something: Could it be that the engine oiling system wasn't primed after the cam install?

I've never read anything that says it needs to be primed, but if the oil galleries, lifters, pushrods, are dry, could it be that amount of time it takes for oil pressure to build the bearing gets damaged from lack of oil?

I wonder.

Jake
 

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