Truck Running Rough

curt 5.7 · 08-06-2008, 08:23 PM

My truck was hard on gas was getting 10mpg, so I check the ERG valve thats not it,put a cat. back in,new 02 sensor plugs.wires,rotor,distributer cap and fuel filter and many other small parts.Still got 10mpg.So pulled the old cam out, the old lifters were mushroomed very bad could hardly get them out put new lifters and cam rods and rockers were put back in the same spots.Set valves one had to be turned down alot more than the others before it would stop ticking about 1 1/2 turns more than the rest.Put everything back together.I unplued the wire on the fire wall and timed it it's at 0 degress.Idles fine in park seems to have more power than before but idles really crappy in any gear.I can hear a sort of chushing noise coming out of the exgaust guessing that valve is burnt.Would that cause it to idle so bad in gear?I also noticed that with the wire on the fire wall plugged in and check it with the timing light it's way off is that how it is?The truck is a 1993 GMC K1500 4x4 5.7

75K30 · 08-06-2008, 08:37 PM

How long did you beak this hydraulic lifter cam?
What type of break in lube did you use for your lifters and cam lobes?
This is unfortunate, but it sounds as though one of the lifters is not working properly.
Did you verify lift on all of the rockers?

curt 5.7 · 08-06-2008, 08:45 PM

I just put the cam in I used some lube that came with it kinda like vasoline.Lift on the rockers?I set the valves should that do the samething?I had to tighten that one valve alot more than the others so I was kinda leaning towards that.I can hear a sort of noise sounds like a timer pulled off the filter, so I could see the injectors sounds the same but never heard this noise before also I can hear it in the cab somewhere around the gas pedal.

75K30 · 08-06-2008, 09:10 PM

There is a very good chance that you have a simple vacuum leak.
However, this single lifter that required additional adjustment has me a little confused.
I use a degree wheel and dial indicator with every cam I install. I use it to verify exactly how much gross lift every lobe has, and to verify that the cam card is close to correct.
This is measured in valve lift, and if you have "one" lobe that went dry, or was damaged during the installation, then this total lift figure is no longer accurate, and this is where your problem will be at.
I am hoping that this is not the case, because there is no other way to fix it, other than replacing the cam and all of the lifters again.
That being said, you will need to pull the valve cover and check to see that this suspect rocker puches the valve open as far as the other valves open.
This might be a little tough to measure, but you will see a reasonable difference that should be verifiable with the naked eye.
If you have one that has not pumped up, or has not accepted oil to pressure it up, you need to address it right away.
Did you prime the engine by turning the oil pump before you installed the dizzy?
This should have been done to get all of the bearings wet again, and get oil to the pushrods.
If you failed to do this, then you may have overtightened the lifter, and this is where your problem is, and the valve is too tight.
It may not be closing all of the way, and you might be on the way to a bent pushrod, or even another bad lifter. Lets hope for neither one.

curt 5.7 · 08-06-2008, 09:29 PM

I will look into the dial indicator.Does it just attach to a reachet?I did not prime the pump was told I didn't have to.I also set the valves while the engine was running.I noticed on the one side that a fair amount of oil came out most of the push rods and the one was really spraying oil it would shoot atleast 3' in a straight stream.On the side where I'am having the problem some of them it's just trickleing out some seems to comeout at about the right rate.

75K30 · 08-06-2008, 10:17 PM

To check the actual gross valve lift, I would remove the rocker and check the amount that the pushrod moves up. This will require a slow movement of the engine, and a careful eye.
This can be compared to other cylinders to make sure that you are obtaining the correct lift, and that a lifter is not going bad.
I recommend using the pushrod as a reference for measurement, and not the valve because there would be some variables such as rocker geometry that could be way off.
This leads me to another idea. Could the rocker that you removed be bent? If the fulrum has had the chance to open up, you might not have the perfect overall ratio, and this too could cause your problem. We nmay be looking at this from the wrong angle here, and you caould just have a faulty rocker. The oil from the top of the pushrods is interesting, and the oil should be pumping out at a decent rate. Always concerns me when stock engines have random oiling issues, but I am not confident that this is your problem. It could have other issues, but these are probably not related.
Maybe switch this rocker with a known to be good one from another cylinder, and see if this fixes the problem. Could be that the thing is not opening the valve all of the way. Not bad for idle, but horrible for any throttle input.
Just throwing some ideas out there. Wish I could see this one for myself.
I believe you are plenty capabale to fix this, so hang in there, I know things can get frustrating, this is probably something simple, and will run like a champ soon enough.

curt 5.7 · 08-07-2008, 06:25 AM

So to check the lift take the coil wire off and the rocker and get someone to turn the engine over while measuring it.I will try changing the rockers later and will price out new rockers and rods.The truck seems fine has plenty of power at idle in park same while moving and sounds fine when in gear and not moving it doesn't sound so good and kinda shakes.I tryed changing the timing and it does matter which degree I change it too it still does this.The higher the degree I go the worse it runs.It is set on 4 degrees now but says it should be on 0 degrees.

75K30 · 08-07-2008, 07:00 AM

I would be concerned that tutning the engine over with the starter would turn far too fast, and you will either ruin your dial indicator, or just never get the correct reading.
You should probably turn the engine by hand.
If you take a couple of measurements here you can measure the lift from the cam lobe (directly from the pushrod) and after the rocker. to compare the difference. You can determine the actual lift and determine whether or not the rocker as bent, or a pushrod has failed.
This should be a pretty quick and easy check. Hopefully you will find some differences here, and it might show you where a problem is.
I wish I knew what this noise was. Lifters do not like to be too tight, and I have a suspicion that the one lifter is slightly on the tight side.
If you loosten up the suspect rocker and lifter, does the noise seem to go away?

leolkfrm · 08-07-2008, 10:33 AM

It sounds like the lifters were partially colapsed when you assembled the top end. I would go back and do it the messy way again with the motor hot and see if it makes a difference, also on the rocker in question make sure that the stud is not pulling out of the head.

08-06-2008, 08:23 PM	#1
curt 5.7 Full Member Join Date: Jun 2008 Posts: 22	Truck Running Rough My truck was hard on gas was getting 10mpg, so I check the ERG valve thats not it,put a cat. back in,new 02 sensor plugs.wires,rotor,distributer cap and fuel filter and many other small parts.Still got 10mpg.So pulled the old cam out, the old lifters were mushroomed very bad could hardly get them out put new lifters and cam rods and rockers were put back in the same spots.Set valves one had to be turned down alot more than the others before it would stop ticking about 1 1/2 turns more than the rest.Put everything back together.I unplued the wire on the fire wall and timed it it's at 0 degress.Idles fine in park seems to have more power than before but idles really crappy in any gear.I can hear a sort of chushing noise coming out of the exgaust guessing that valve is burnt.Would that cause it to idle so bad in gear?I also noticed that with the wire on the fire wall plugged in and check it with the timing light it's way off is that how it is?The truck is a 1993 GMC K1500 4x4 5.7

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08-06-2008, 08:37 PM	#2
75K30 Senior Member Join Date: Jul 2006 Posts: 2,544	How long did you beak this hydraulic lifter cam? What type of break in lube did you use for your lifters and cam lobes? This is unfortunate, but it sounds as though one of the lifters is not working properly. Did you verify lift on all of the rockers?

08-06-2008, 08:45 PM	#3
curt 5.7 Full Member Join Date: Jun 2008 Posts: 22	I just put the cam in I used some lube that came with it kinda like vasoline.Lift on the rockers?I set the valves should that do the samething?I had to tighten that one valve alot more than the others so I was kinda leaning towards that.I can hear a sort of noise sounds like a timer pulled off the filter, so I could see the injectors sounds the same but never heard this noise before also I can hear it in the cab somewhere around the gas pedal.

08-06-2008, 09:10 PM	#4
75K30 Senior Member Join Date: Jul 2006 Posts: 2,544	There is a very good chance that you have a simple vacuum leak. However, this single lifter that required additional adjustment has me a little confused. I use a degree wheel and dial indicator with every cam I install. I use it to verify exactly how much gross lift every lobe has, and to verify that the cam card is close to correct. This is measured in valve lift, and if you have "one" lobe that went dry, or was damaged during the installation, then this total lift figure is no longer accurate, and this is where your problem will be at. I am hoping that this is not the case, because there is no other way to fix it, other than replacing the cam and all of the lifters again. That being said, you will need to pull the valve cover and check to see that this suspect rocker puches the valve open as far as the other valves open. This might be a little tough to measure, but you will see a reasonable difference that should be verifiable with the naked eye. If you have one that has not pumped up, or has not accepted oil to pressure it up, you need to address it right away. Did you prime the engine by turning the oil pump before you installed the dizzy? This should have been done to get all of the bearings wet again, and get oil to the pushrods. If you failed to do this, then you may have overtightened the lifter, and this is where your problem is, and the valve is too tight. It may not be closing all of the way, and you might be on the way to a bent pushrod, or even another bad lifter. Lets hope for neither one.

08-06-2008, 09:29 PM	#5
curt 5.7 Full Member Join Date: Jun 2008 Posts: 22	I will look into the dial indicator.Does it just attach to a reachet?I did not prime the pump was told I didn't have to.I also set the valves while the engine was running.I noticed on the one side that a fair amount of oil came out most of the push rods and the one was really spraying oil it would shoot atleast 3' in a straight stream.On the side where I'am having the problem some of them it's just trickleing out some seems to comeout at about the right rate.

08-06-2008, 10:17 PM	#6
75K30 Senior Member Join Date: Jul 2006 Posts: 2,544	To check the actual gross valve lift, I would remove the rocker and check the amount that the pushrod moves up. This will require a slow movement of the engine, and a careful eye. This can be compared to other cylinders to make sure that you are obtaining the correct lift, and that a lifter is not going bad. I recommend using the pushrod as a reference for measurement, and not the valve because there would be some variables such as rocker geometry that could be way off. This leads me to another idea. Could the rocker that you removed be bent? If the fulrum has had the chance to open up, you might not have the perfect overall ratio, and this too could cause your problem. We nmay be looking at this from the wrong angle here, and you caould just have a faulty rocker. The oil from the top of the pushrods is interesting, and the oil should be pumping out at a decent rate. Always concerns me when stock engines have random oiling issues, but I am not confident that this is your problem. It could have other issues, but these are probably not related. Maybe switch this rocker with a known to be good one from another cylinder, and see if this fixes the problem. Could be that the thing is not opening the valve all of the way. Not bad for idle, but horrible for any throttle input. Just throwing some ideas out there. Wish I could see this one for myself. I believe you are plenty capabale to fix this, so hang in there, I know things can get frustrating, this is probably something simple, and will run like a champ soon enough.

08-07-2008, 06:25 AM	#7
curt 5.7 Full Member Join Date: Jun 2008 Posts: 22	So to check the lift take the coil wire off and the rocker and get someone to turn the engine over while measuring it.I will try changing the rockers later and will price out new rockers and rods.The truck seems fine has plenty of power at idle in park same while moving and sounds fine when in gear and not moving it doesn't sound so good and kinda shakes.I tryed changing the timing and it does matter which degree I change it too it still does this.The higher the degree I go the worse it runs.It is set on 4 degrees now but says it should be on 0 degrees.

08-07-2008, 07:00 AM	#8
75K30 Senior Member Join Date: Jul 2006 Posts: 2,544	I would be concerned that tutning the engine over with the starter would turn far too fast, and you will either ruin your dial indicator, or just never get the correct reading. You should probably turn the engine by hand. If you take a couple of measurements here you can measure the lift from the cam lobe (directly from the pushrod) and after the rocker. to compare the difference. You can determine the actual lift and determine whether or not the rocker as bent, or a pushrod has failed. This should be a pretty quick and easy check. Hopefully you will find some differences here, and it might show you where a problem is. I wish I knew what this noise was. Lifters do not like to be too tight, and I have a suspicion that the one lifter is slightly on the tight side. If you loosten up the suspect rocker and lifter, does the noise seem to go away?

08-07-2008, 10:33 AM	#9
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 1,074	It sounds like the lifters were partially colapsed when you assembled the top end. I would go back and do it the messy way again with the motor hot and see if it makes a difference, also on the rocker in question make sure that the stud is not pulling out of the head.