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I was worry you had some exhaust valve issue. That pretty much explained your double pulse. Good luck and wishing you don't have a burnt valve. Hope it is just a image issue, but that little missing piece would fit with all your diagnostic results. I used the OEM heads gasket.
I was worry you had some exhaust valve issue. That pretty much explained your double pulse. Good luck and wishing you don't have a burnt valve. Hope it is just a image issue, but that little missing piece would fit with all your diagnostic results. I used the OEM heads gasket.
Well, burnt valve, or trash on the seat, either way the head should come off. I took another look with the trash borescope (it has no close focus), and I could not see light through that black triangle. Perhaps it's soot, perhaps not. But I'll know soon.
I'll pick up a set of OEM head gaskets. I s'pose I should replace the head bolts, too. The engine has 60K miles on it.
One other friendly suggestion... Consider going with Head Studs. I get that they are not cheap, and some people will argue that you can't remove the heads as easily (which is wrong - the studs are not Loctited in place, they are tightened finger tight, and normally have a small allen head recess in the top - so they can be unscrewed from the block if needed to remove the head while the motor is in the car). I've seen articles that show significantly better and more uniform clamping loads when head studs are used rather than head bolts. This is probably more important if Boost is a part of the engines future - but since the engine is out, and the head bolts are already off - it's at least worth considering it.....
One other friendly suggestion... Consider going with Head Studs. I get that they are not cheap, and some people will argue that you can't remove the heads as easily (which is wrong - the studs are not Loctited in place, they are tightened finger tight, and normally have a small allen head recess in the top - so they can be unscrewed from the block if needed to remove the head while the motor is in the car). I've seen articles that show significantly better and more uniform clamping loads when head studs are used rather than head bolts. This is probably more important if Boost is a part of the engines future - but since the engine is out, and the head bolts are already off - it's at least worth considering it.....
You can remove the heads without removing the studs, but if for some reason you wanted to they are easy to take out like you said
Well, burnt valve, or trash on the seat, either way the head should come off. I took another look with the trash borescope (it has no close focus), and I could not see light through that black triangle. Perhaps it's soot, perhaps not. But I'll know soon.
I'll pick up a set of OEM head gaskets. I s'pose I should replace the head bolts, too. The engine has 60K miles on it.
To use head studs properly is to dissemble the engine completely and bore with a deck plate clamped using the studs intended for the engine.
What they mean its more difficult to remove the heads with the studs because the head has to rise much higher during removal, often something like the hood or part of the car is in the way. On some engines it can be the timing cover or related to the tensioner like the sr20/rb/2j engines.
No point in head studs at < 1000hp. People have successfully 1200rwhp using factory gaskets and factory head bolts.
Factory bolts torque to yield are not technically re-usable but they have been found more than adequate when re-used properly in the hands of experienced mechanic. They have even been meausured in tensile stress using appropriate sample size and statistical interface and found that he used head bolts are just as strong or stronger when re-used once.
I've ordered a set of ARP bolts (not studs) and GM head gaskets. I also ordered valve seals. If it turns out I need to replace the valve, I might do a "while I'm in there" spring replacement as well. I have a set of 12499224 valve springs, so I should probably just go ahead and do that to save grief down the road.
I've ordered a set of ARP bolts (not studs) and GM head gaskets. I also ordered valve seals. If it turns out I need to replace the valve, I might do a "while I'm in there" spring replacement as well. I have a set of 12499224 valve springs, so I should probably just go ahead and do that to save grief down the road.
As MetalMan said, change the YELLOW springs. I bought my 02 C5Z with 38k on it. After extensive research learning about the car (My first Corvette) I discovered that my car had the yellow springs after sending a scope down the oil filler tube. What spooked me the most was that some guys broke a spring on a track day and some while cruising down the road at 2000RPMS. The latter was the clincher for me. While in there I also installed a CHE Trunion Kit. I prefer to be Uber thorough when I fix things.
Do what you want with this information and good luck!
As MetalMan said, change the YELLOW springs. I bought my 02 C5Z with 38k on it. After extensive research learning about the car (My first Corvette) I discovered that my car had the yellow springs after sending a scope down the oil filler tube. What spooked me the most was that some guys broke a spring on a track day and some while cruising down the road at 2000RPMS. The latter was the clincher for me. While in there I also installed a CHE Trunion Kit. I prefer to be Uber thorough when I fix things.
Do what you want with this information and good luck!
Erik
I have a feeling I'll be replacing those springs. Thanks!
Parts have arrived, so I pulled the head. The gasket was a FelPro replacement, so someone has been in there before. Below are the valves, #4 intake and exhaust have been cleaned with Sea Foam and Scotchbrite. The #4 exhaust valve had a burr on it, which may have been the issue (or the chunk of debris that was holding it open). I'll clean up the head as best I can, and hone all the valves, then compression test again. Since I've gone this far, I'll swap out the springs and valve seals, too.
Any other "while I'm in there" projects? Is Sea Foam safe enough for the aluminum, or should I be rinsing it out with something? Any other tricks to clean the carbon? A razor worked great on the flat quench area. I'll likely do the same to the pistons, and plan to change the oil (again) once it's all back together.
Green Scotch Bright with paint thinner. You can use a brown, just don’t get too enthusiastic with it. There are other brands of brown pads that don’t have the added abrasives which is a third alternative(more coarse than the green, but without the added abrasives).
Originally Posted by Bikespace
Update:
Parts have arrived, so I pulled the head. The gasket was a FelPro replacement, so someone has been in there before. Below are the valves, #4 intake and exhaust have been cleaned with Sea Foam and Scotchbrite. The #4 exhaust valve had a burr on it, which may have been the issue (or the chunk of debris that was holding it open). I'll clean up the head as best I can, and hone all the valves, then compression test again. Since I've gone this far, I'll swap out the springs and valve seals, too.
Any other "while I'm in there" projects? Is Sea Foam safe enough for the aluminum, or should I be rinsing it out with something? Any other tricks to clean the carbon? A razor worked great on the flat quench area. I'll likely do the same to the pistons, and plan to change the oil (again) once it's all back together.
mineral spirits and a bronze brush on carbon is fine. But make sure its a real bronze brush and not a steel brush coated in bronze.
Alcohol can break up carbon (E85 fuel is 85% alcohol and 15% gasoline) If you have high % alcohol.
Brake cleaner is good but it dries metal out quickly and that leads to rust. This is why I like mineral spirits it leaves an oily coating while you clean.
Try not to scrape too much with razor unless you are confident not to gouge the aluminum or deck.
Never use air or electric tools to do these cleaning jobs. Do not use a wire wheel however tempting.
The Factory service manual probably says to use acetone on the deck before assembly. This is what I do for the MLS gaskets, blow out the bolt holes and acetone on the deck prep after straight edge.
Stuff to do while in there is just basics. Change the oil when finished. keep the cylinders wet with oil so they don't rust.
I like to wash down the piston rings with mineral spirits and turn the motor over slowly to loosen up piston ring carbon buildup.
Don't get tempted to do things to the heads. Just R&R. Its like the less you change, the better it turns out.
For the head that is off, I would clean it well, especially the valve seats and also the rest of the valves like you have done for the two clean ones. Then I would lap all of them to insure that none are bent.
I cleaned the valves, replaced the springs and valve seals, lapped the valves, and cleaned up as much carbon as I could. With new GM head gaskets and ARP bolts, the head is back on. Compression is now:
2 210
4 210
6 210
8 180
I just pulled the other head off, and I'll do the same on that side.
Well. If Its number 8 then.... I compression tested 12 junkyard engines and number 8 almost always had low compression than all others. I would attribute to carbon buildup in the ring pack perhaps. Maybe something to do with the position or manifold design (oil ingestion preference) or pcv or whatever. Could even be low because of the manifold design shape itself, air pressure or harmonic activity stealing some volume. My 2002 5.3 had 154 on all cylinders except #8 was like 135psi at 180,000 miles and that was the best one out of 12 engines that I tested so its the one I took and used and I put 55,000 miles on it already fine 600rwhp. I put a little oil in the cylinder it went up almost back to 155psi after I did the head gaskets back in 2017. I think if you put a little oil in the cylinder it may go back up which means rings. But it doesn't mean thats how it will run. Maybe some seafoam will help when its running.
Bottom line is I wouldn't worry about it but at the same time consider what you might do to try and help it , clean it up if possible.
Well. If Its number 8 then.... I compression tested 12 junkyard engines and number 8 almost always had low compression than all others. I would attribute to carbon buildup in the ring pack perhaps. Maybe something to do with the position or manifold design (oil ingestion preference) or pcv or whatever. Could even be low because of the manifold design shape itself, air pressure or harmonic activity stealing some volume. My 2002 5.3 had 154 on all cylinders except #8 was like 135psi at 180,000 miles and that was the best one out of 12 engines that I tested so its the one I took and used and I put 55,000 miles on it already fine 600rwhp. I put a little oil in the cylinder it went up almost back to 155psi after I did the head gaskets back in 2017. I think if you put a little oil in the cylinder it may go back up which means rings. But it doesn't mean thats how it will run. Maybe some seafoam will help when its running.
Bottom line is I wouldn't worry about it but at the same time consider what you might do to try and help it , clean it up if possible.
Pretty interesting experience. I've only had one LS, my current 2001 LS6. Last year I checked compression at just under 76k miles: Driver-side, front-rear: 195/189, 192, 195, 193 psi. Passenger-side, front-rear: 201, 186, 196, 199 psi.
To use head studs properly is to dissemble the engine completely and bore with a deck plate clamped using the studs intended for the engine.
What they mean its more difficult to remove the heads with the studs because the head has to rise much higher during removal, often something like the hood or part of the car is in the way. On some engines it can be the timing cover or related to the tensioner like the sr20/rb/2j engines.
No point in head studs at < 1000hp. People have successfully 1200rwhp using factory gaskets and factory head bolts.
Factory bolts torque to yield are not technically re-usable but they have been found more than adequate when re-used properly in the hands of experienced mechanic. They have even been meausured in tensile stress using appropriate sample size and statistical interface and found that he used head bolts are just as strong or stronger when re-used once.
"re-used properly in the hands of experienced mechanic. /stronger":
if you follow the torque to angle procedure you will break them. you have to torque them to the specified/unspecified torque. you can go a bit higher, because they have work hardened during the original installation and are "stronger" now. not easy to do.
"re-used properly in the hands of experienced mechanic. /stronger":
if you follow the torque to angle procedure you will break them. you have to torque them to the specified/unspecified torque. you can go a bit higher, because they have work hardened during the original installation and are "stronger" now. not easy to do.
Of course you cant use torque to angle on an already yielded and stretched tty bolt. That is why I suggested hands of experienced mechanic. Although perhaps mechanical engineer is more appropriate. When I re-used my TTY bolts I can easily feel the starting point of re-entering plastic deformation which is how you know you've surpassed the original torque while the bolt is being stretched longer than originally when used the first time around. You can go just a bit beyond that point and wind up with superior head clamping force and a longer more stretched out bolt which will work fine like the stock bolt should. I wouldn't use them anymore than 3 times though and even 2 is enough for me, crazy not soup
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