LT4 - Top end noise
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
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From: Orlando FL
LT4 - Top end noise
Well my recent LT4 purchase looks like it will be costing me even more money. It is a good thing I hardly paid anything for it. Today I diagnosed part of the top end ticking noise I was hearnig at idle.
I removed both valve covers and inspected the lifters. The rocker on the right side of cylinder #7 was very loose. I tried to tighten it but the nut will not go any further. A close inspection showed me that something has got to be wrong in there. I removed the rocker and noticed some wear marks on the roller tip end where it meets springs. I removed the pushrod and it appears to be straight as an arrow. It also appears to be extended the same length as the others eliminating the possibility of a collapsed lifter. I inspected the spring and could not tell if it is broken. It does however look more compressed even though there is no pressure on the top. Can anyone give me any insight to this? At this time I am assuming the worst - a bent valve.
I removed both valve covers and inspected the lifters. The rocker on the right side of cylinder #7 was very loose. I tried to tighten it but the nut will not go any further. A close inspection showed me that something has got to be wrong in there. I removed the rocker and noticed some wear marks on the roller tip end where it meets springs. I removed the pushrod and it appears to be straight as an arrow. It also appears to be extended the same length as the others eliminating the possibility of a collapsed lifter. I inspected the spring and could not tell if it is broken. It does however look more compressed even though there is no pressure on the top. Can anyone give me any insight to this? At this time I am assuming the worst - a bent valve.
Last edited by quiksilver458; Sep 17, 2009 at 05:33 PM.
Former Vendor
Joined: Nov 2006
Posts: 2,482
Likes: 3
From: Carmichael ca
If the valve was bent the car would have been running on 7 cylinders, so a dead miss would have been apparent. Can you pull up on the valve, usually with a broken spring you can move the valve. How does the top of the valve look, mushroomed?
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
Likes: 0
From: Orlando FL
Working on the photos as I can not seem to get a clear shot of it. As for pulling up on the valve. I had pulled and pushed and I can not make it move either way. I just fired the motor with cover off to see if it was in fact moving. The push rod is extending and rotating the rocker which does apply some pressure to the valve, but the motion of the valve seems very short. The valve looks normal. No mushroom affect or anything. Looks shiny and new to me.
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
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From: Orlando FL
These are the best I can do. I have taken 30 plus and can not seem to get it where it shows the right valve sitting lower than the left. It is not much, maybe 1/8-1/12th of an inch. It is just enough to allow the rocker to come off roller and swivel to either side.
Last edited by quiksilver458; Sep 17, 2009 at 06:47 PM.
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From: Rolla Missouri
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Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 195
From: folsom california
on my lt4 high miler the valve gear was in good shape except for one lifter; the rocker body where it forms "ears" next to the roller tip had been worn down and damaged by the tip of the valve stem; this was a self perptuating failure because these "ears" locate the pushrod and serve the same purpose as more conventional "push rod guide plate"; as these ears are worn or become damaged, the more the rocker arm wants to rotate off the valve stem tip, and the faster the failure cycle accelerates. There may be something similiar happenning with your engine.
Also, one idiosynchrousy of the lt4 (versus the lt1 or any other chevy small block built since 1955) is that the rocker arms are mounted on a pedestal type mount and the mounting nut, once tightened, allows no further adjustment.
Good luck with your lt4, its a magnificent, albeit expensive, engine in what was arguably the best c4, but truthfully, if money is an issue I would consider an earlier car with an L98 (conventional) engine.
Also, one idiosynchrousy of the lt4 (versus the lt1 or any other chevy small block built since 1955) is that the rocker arms are mounted on a pedestal type mount and the mounting nut, once tightened, allows no further adjustment.
Good luck with your lt4, its a magnificent, albeit expensive, engine in what was arguably the best c4, but truthfully, if money is an issue I would consider an earlier car with an L98 (conventional) engine.
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Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
Likes: 0
From: Orlando FL
Yeah - for a 93k mile motor - it sure doesnt seem like it has been mechanically taken care of. Cosmetically, this thing is an easy 8 out of 10. The paint is perfect with the exception of some minor sun damage to top of rear clip. The interior is very clean with minimal wear on the driver seat bolster. I will most likely replace the cover to make it perfect.
Anyway - I pulled a few more push rods and it appears there is quite a bit of build up in the motor. Perhaps this buildup has stuck the valve some? I'd hate to have to remove the head for something stupid like that, but it almost sounds like its my only choice.
I may check autozone and see if they have a spring compressor loaner tool I can rent. Pull the springs, and mess with the valve some. See if it can pull out further than it is.
Anyway - I pulled a few more push rods and it appears there is quite a bit of build up in the motor. Perhaps this buildup has stuck the valve some? I'd hate to have to remove the head for something stupid like that, but it almost sounds like its my only choice.
I may check autozone and see if they have a spring compressor loaner tool I can rent. Pull the springs, and mess with the valve some. See if it can pull out further than it is.
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
One thing you might try, although there is a chance that this really uncover any problems in the engine. But those would come to surface eventually.
Try the SeaFoam treatment. Put 1/3 can in the crankcase, preferrably with fresh synthetic. Change after about 200 miles. If your not familiar with it, it is a petroleum based product that cleans sludge and oil varnish. It appears you have quite a bit of that going on, and it could be causing a lifter to stick or clogging the oil passage through the push rod.
You can also put 1/3 gan in the gas to clean injectors and fuel lines. And then slowly suck the rest of it through the brake booster hose to clean out the heads and valve seats. If you search "seafoam" I know there is a tutorial on here. It works pretty well.
As far as the rocker nuts, in the LT4 they are non-adjustable. They simply torque to 18 ft lbs.
Try the SeaFoam treatment. Put 1/3 can in the crankcase, preferrably with fresh synthetic. Change after about 200 miles. If your not familiar with it, it is a petroleum based product that cleans sludge and oil varnish. It appears you have quite a bit of that going on, and it could be causing a lifter to stick or clogging the oil passage through the push rod.
You can also put 1/3 gan in the gas to clean injectors and fuel lines. And then slowly suck the rest of it through the brake booster hose to clean out the heads and valve seats. If you search "seafoam" I know there is a tutorial on here. It works pretty well.
As far as the rocker nuts, in the LT4 they are non-adjustable. They simply torque to 18 ft lbs.
Drifting
Joined: May 2008
Posts: 1,692
Likes: 489
From: Denver, NC
Yeah - for a 93k mile motor - it sure doesnt seem like it has been mechanically taken care of. Cosmetically, this thing is an easy 8 out of 10. The paint is perfect with the exception of some minor sun damage to top of rear clip. The interior is very clean with minimal wear on the driver seat bolster. I will most likely replace the cover to make it perfect.
Anyway - I pulled a few more push rods and it appears there is quite a bit of build up in the motor. Perhaps this buildup has stuck the valve some? I'd hate to have to remove the head for something stupid like that, but it almost sounds like its my only choice.
I may check autozone and see if they have a spring compressor loaner tool I can rent. Pull the springs, and mess with the valve some. See if it can pull out further than it is.
Anyway - I pulled a few more push rods and it appears there is quite a bit of build up in the motor. Perhaps this buildup has stuck the valve some? I'd hate to have to remove the head for something stupid like that, but it almost sounds like its my only choice.
I may check autozone and see if they have a spring compressor loaner tool I can rent. Pull the springs, and mess with the valve some. See if it can pull out further than it is.
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
One thing you might try, although there is a chance that this really uncover any problems in the engine. But those would come to surface eventually.
Try the SeaFoam treatment. Put 1/3 can in the crankcase, preferrably with fresh synthetic. Change after about 200 miles. If your not familiar with it, it is a petroleum based product that cleans sludge and oil varnish. It appears you have quite a bit of that going on, and it could be causing a lifter to stick or clogging the oil passage through the push rod.
You can also put 1/3 gan in the gas to clean injectors and fuel lines. And then slowly suck the rest of it through the brake booster hose to clean out the heads and valve seats. If you search "seafoam" I know there is a tutorial on here. It works pretty well.
As far as the rocker nuts, in the LT4 they are non-adjustable. They simply torque to 18 ft lbs.
Try the SeaFoam treatment. Put 1/3 can in the crankcase, preferrably with fresh synthetic. Change after about 200 miles. If your not familiar with it, it is a petroleum based product that cleans sludge and oil varnish. It appears you have quite a bit of that going on, and it could be causing a lifter to stick or clogging the oil passage through the push rod.
You can also put 1/3 gan in the gas to clean injectors and fuel lines. And then slowly suck the rest of it through the brake booster hose to clean out the heads and valve seats. If you search "seafoam" I know there is a tutorial on here. It works pretty well.
As far as the rocker nuts, in the LT4 they are non-adjustable. They simply torque to 18 ft lbs.
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
Likes: 0
From: Orlando FL
No doubt it has not seen regular oil changes. I suppose I should have added that this car has been sitting for 1.5 years as well. So I know there is a great deal of build up in there. From the previous post - I will be running some seafoam through the system as soon as the new water pump arrives.
Thanks everyone for the advice!
Melting Slicks
Joined: Nov 2004
Posts: 2,799
Likes: 2
From: Cape Coral FL
and DON'T DRIVE IT the first time you do this... run it for about a half hour to 45 minutes and change oil and filter. I never recommend driving with any flush agent in the crankcase for any length of time.
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
No doubt it has not seen regular oil changes. I suppose I should have added that this car has been sitting for 1.5 years as well. So I know there is a great deal of build up in there. From the previous post - I will be running some seafoam through the system as soon as the new water pump arrives.
Thanks everyone for the advice!
Thanks everyone for the advice!
I just don't get how someone can have a car like that and just totally neglet things like oil changes.
Last edited by lt4obsesses; Sep 20, 2009 at 08:13 PM.
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
Likes: 0
From: Orlando FL
Well here is an update guys. I removed the heads and discovered the culprit to my problem. A valve seat had fallen loose preventing the one valve from closing completely. Both heads were removed and reconditioned here locally. I of course had a few extras done since they were off and all. 
Anyway, the reassembly has begun and I have a question.
The hard coolant line that bolts to the rear of each head has my stumped. When I removed the banjo style bolts, both head had two rubber/metal washers installed. These washers are the AC line style washer and did not make sense to me in that location. What washer IF any should be on these two bolts? If a banjo bolt had a washer, it would be copper if I am not mistaken.
Thanks!
Anyway, the reassembly has begun and I have a question.The hard coolant line that bolts to the rear of each head has my stumped. When I removed the banjo style bolts, both head had two rubber/metal washers installed. These washers are the AC line style washer and did not make sense to me in that location. What washer IF any should be on these two bolts? If a banjo bolt had a washer, it would be copper if I am not mistaken.
Thanks!