What are the tell-tale signs of dropped valve?
03-06-2011, 09:32 PM
#1
Teching In
Thread Starter
Join Date: Feb 2009
Posts: 20
Likes: 0
Received 0 Likes
on
0 Posts
What are the tell-tale signs of dropped valve? I am running a highly modded '01 TA (465 RWHP on the dyno). After a tune that unlocked about 50 RWHP the car was running phenomenally. Then, I was putt-putting home from work at about 30 mph when I noticed my car sounded weird and had significant power loss. Because I have a tune, my car won't pick up a misfire. So, I did what anyone with half a brain would do, I changed plugs and wires. It did help the idle a bit, but it was definitely still missing. Along with the missing idle, there was a ticking sound coming from the driver side of the engine. I gave the car very minor gas pedal to see if it got louder and faster and it did. After cruising LS1Tech.com for hours, I decided to take off my valve covers. What I found was my #7 intake valve spring broken. After reading several forums on this site, I know it will be expensive to fix. I am just wondering what, if any, are the tell-tale signs of a dropped valve. Is the ticking sound I was hearing the valve hitting the piston? I have ported LS6 heads (243 cast) with, what I suspect, stock LS6 springs. Any info would be greatly appreciated.
03-06-2011, 09:47 PM
#2
Tell tale sign of a dropped valve, is a broken valve spring, and no valve to be seen.
Ive had it happen in 2 different cars. First one, the car stuttered and died.. It ruined a piston and rod. (https://ls1tech.com/forums/generatio...l#post13804872)
The second one, was making a LOUD clicking sound, if it would stay running.. The valve dropped, broke the head off the valve, and wedging it back into the seat sideways. The clicking was the valve knocking a hole in the piston. (https://ls1tech.com/forums/generatio...st-update.html)
Ive had it happen in 2 different cars. First one, the car stuttered and died.. It ruined a piston and rod. (https://ls1tech.com/forums/generatio...l#post13804872)
The second one, was making a LOUD clicking sound, if it would stay running.. The valve dropped, broke the head off the valve, and wedging it back into the seat sideways. The clicking was the valve knocking a hole in the piston. (https://ls1tech.com/forums/generatio...st-update.html)
03-06-2011, 10:26 PM
#3
Remove the spark plug for that cylinder and shine a flashlight down in there. If the valve dropped you will be able to see all kinds of ding marks on top of the piston.
Wait...a minute...didnt you say you removed the valve cover to find a broken valve spring? The valve locks should be laying in there somewhere and the end of your valve stem not visible anymore.
Good Luck with all that!
Wait...a minute...didnt you say you removed the valve cover to find a broken valve spring? The valve locks should be laying in there somewhere and the end of your valve stem not visible anymore.
Good Luck with all that!
Trending Topics
03-07-2011, 10:52 PM
#8
Teching In
Thread Starter
Join Date: Feb 2009
Posts: 20
Likes: 0
Received 0 Likes
on
0 Posts
I surely know a broken spring when I see one. I am fully capable of removing my heads and looking to see if I, indeed, dropped a valve. I am asking those who are knowledgeable on these engines as a quick assessment of possible damage. Most of my experience on F-bodies is on an LT1 where I did a complete top-end rebuild, myself, with just a background in aircraft maintenance (18.5 years on the F-16), and I was able to achieve 439 RWHP. The heads came prebuilt and I all I did was adjust the valves (while the engine was running). I have no experience with valves aside from that. From what I see on most of these forums is that there are just a handful of guys who actually know what they are doing. The rest are either asking questions or criticizing those who are asking.
03-07-2011, 11:18 PM
#9
Well it sounds like you are a pro.....
Look here, this is a broken spring but he was lucky the valve did not drop as you can see the valve stem is still at the top of the spring with the retainer.
THis guy was not so lucky, broken valve spring and dropped valve as you can see the stem is no where to be found in the center of the spring and you can see the retainer and keepers lying off to the right.
I would imagine if your engine is still running that you havent dropped the valve yet..... Dont run the engine until you replace the broken valve spring
Look here, this is a broken spring but he was lucky the valve did not drop as you can see the valve stem is still at the top of the spring with the retainer.
THis guy was not so lucky, broken valve spring and dropped valve as you can see the stem is no where to be found in the center of the spring and you can see the retainer and keepers lying off to the right.
I would imagine if your engine is still running that you havent dropped the valve yet..... Dont run the engine until you replace the broken valve spring
Last edited by Mart00SS; 03-08-2011 at 11:50 AM.
03-07-2011, 11:24 PM
#10
If youre lucky it wont get sucked in completely, my experience was a failed retainer but the piston kissed it just right and it just bent the valve and it didnt drop... it did pretty much no damage except for a small flycut looking ding on top of my piston.... if youre looking for a tell tale sign, i dont think you sucked it in completely..
03-08-2011, 08:49 AM
#11
Teching In
Thread Starter
Join Date: Feb 2009
Posts: 20
Likes: 0
Received 0 Likes
on
0 Posts
Thanks a lot guys!!! I really appreciate all the feedback I have gotten. The pics are really informative. I did not drop my valve based on the pics you guys posted. I located the broken valve spring and immediately put the springs and a top end gasket kit on order. I know I HAVE to pull my head to ensure no further damage was done. I'm hoping my valve did not kiss my piston, however, I need to be sure. I want everyone to know, I was by no means trying to be rude to anyone, but I came here for advice from the pros, not criticism for asking a question. I definitely got the answer I was seeking and I really appreciate it!
03-08-2011, 09:17 AM
#12
i ran mine after i dropped a valve, i just bent the shaft and it stayed up there.. the ding was there but i didnt want to rebuild the damn thing so i just left it.. drove it for another year with cc503 cam running low 12s.. if it did hit yours a bit and youre like me, run the damn thing, consider it already fly cut.. 
03-08-2011, 11:56 AM
#13
If the valve is still up, replace the spring with whatever you've got laying around and do a compression test on that cyl
If it builds compression like the rest of the cyls, replace the spring and dont worry about it. If you've got low/no compression, the valve is bent and the head needs to be rebuilt
Dont drive it until you know the extent of the damage
If it builds compression like the rest of the cyls, replace the spring and dont worry about it. If you've got low/no compression, the valve is bent and the head needs to be rebuilt
Dont drive it until you know the extent of the damage
03-08-2011, 11:34 PM
#16
Teching In
Thread Starter
Join Date: Feb 2009
Posts: 20
Likes: 0
Received 0 Likes
on
0 Posts
What sucks about my car is that I bought it prebuilt. I came with tons of work done to it and a shitty tune. I bought it from a dealership in Utah, fairly cheap for the mileage, mostly because the car has no cats.In Utah dealerships can't legally sell cars without emissions without a written statement. Needless to say, I took the gamble for the price. It looks like it has stock LS6 heads and stock LS6 springs running on a Comp Cams # 54-000-11 cam. I need to find my cam card that has the specifics because these cams are custom milled to fit certain applications. I'm pretty sure I'm looking at about a .605/.615 lift. I'm definitely going with dual valve springs, any suggestions?
03-08-2011, 11:41 PM
#17
Well, if you have to rebuild anything, remove the cam and have it sent out to be cam doctored. It will ensure you the numbers are in fact correct. There are a couple sponsors on here that offer the service. Probably a good way to spend 25$. That is if you can't find or trust the cam card.
I am guessing that you meant the head was milled to mate with the cam. Or was it a regrind? Either way, if you are unsure of the mileage on the springs, i would without a doubt say its time to replace them.
I am guessing that you meant the head was milled to mate with the cam. Or was it a regrind? Either way, if you are unsure of the mileage on the springs, i would without a doubt say its time to replace them.
03-08-2011, 11:43 PM
#18
.615 lift on stock springs? I can see using factory rockers but springs? ... What kind of fucktard would do that? Surely they were replaced before. Do you have pics of your springs? I'm just curious.