Valves banging pistons and bent and broken push rods...
Thread Starter
On The Tree
Joined: Nov 2007
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Valves banging pistons and bent and broken push rods... So Im rebuilding my LS1 and there are small marks in the pistons saying the valves have been hitting them. The valves look fine and the pistons should still be good. The valve springs are fully in tact and stiff with only 30k miles on the engine.
Do the timing chains on the vortecs ever jump?
I was just gunna clean it all up, maybe do a valve job, and put new pushrods in and put it back in but putting the LS1 in the unibody is SSOOOO much work I really dont want to take a chance at having a problem that I overlooked. Can anyone think of anything? My best guess was a faulty sensor firing the plugs to far btdc causing over compression when the valves open, bending the pushrods, sticking the valves in the open position then getting them clunked back down by the piston. Does that sound legit or do you guys have any better ideas? Thanks!
Do the timing chains on the vortecs ever jump?
I was just gunna clean it all up, maybe do a valve job, and put new pushrods in and put it back in but putting the LS1 in the unibody is SSOOOO much work I really dont want to take a chance at having a problem that I overlooked. Can anyone think of anything? My best guess was a faulty sensor firing the plugs to far btdc causing over compression when the valves open, bending the pushrods, sticking the valves in the open position then getting them clunked back down by the piston. Does that sound legit or do you guys have any better ideas? Thanks!
Is the car a manual?? Sounds like a missed shift, I have seen numerous bent pushrods from the valve hitting the piston with no valve damage. The pistons will be fine as long as they are just lightly indented, you will want to smooth out the burs on the pistons to keep them from causing pre-ignition. Hope it helps. There really isnt a sensor that could cause this, just sounds like it was over reved. Hope it helps
Thread Starter
On The Tree
Joined: Nov 2007
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OK I also forgot to mention this, there was a ticking noise for a long time that progressively got louder until one of the pushrods snapped all the way in half. The car is a manuel with the rev limited set at 6 and I drive very good, never really shift wrong. At the exact moment it blew I had it at about 5,300 rpm and I believe it was related to the ticking. So you think just assemble the thing back together and it will be ok?
Sounds like a missed shift to me as well. Don't assume valves are straight because they look good, take them out and check em. Stainless hitting aluminum won't gouge it but can bend it. ticking sound was your valve slamming shut with bent pushrod. If it were me, check valves, new springs, lifters, pushrods, and pistons
It has all teh signs of a missed shift / mechanical over-rev from selecting too low a gear. Either that or too large a cam, or the timing was off a tooth. Check it all, and replace anything that might have been tweaked in the valvetrain.
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Now let me get this straight. Some unknown faulty sensor caused your spark to occur BTDC(which it always does anyway) causing over compression when the valves opened(variable valve timing Yeah, but variable compression is a new one). When the valves are open you don't have any compression let alone over compression. This condition then caused the pushrods to bend which in turn forced the valves to stick open(goodbye compression) and then the pistons clunked the valves back down to exactly where it isn't stated, but it's probably safe to assumed not to the point that compression was restored. HELL NO, that doesn't sound legit. If my engine did all the things you described and I wasn't running 90% nitro or higher I'd call the Pope and ask for an exorcism. The timing chains don't jump at least not a 30K miles. Why would you continue to drive a vehicle that had a loud ticking noise for a very long time that got progressively worse? That's a receipe for disaster which has now happened. You need to tear the top end down and examine everything(pushrods, lifters, springs, valves, valve guides, valve seats, piston crowns, etc.) to look for problems and replace everything that shows signs of a problem. Next time you hear a ticking noise don't just keep driving the thing.
Last edited by eallanboggs; Nov 30, 2007 at 09:18 PM.
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Verdad Gallardo No offense. I'm all for doing work by yourself and if you are confident, go for it. But I just read the whole over compression thing. Dude, not gonna happen. Don't know where that came from. Rev limiter doesn't matter if you are at 6000 rpm's in third gear and put it in second instead of fourth. You may be a good driver, but it does happen. To bend a pushrod, and drive it till it breaks is a huge no no. Don't assume everything is OK. Don't over look anything. If you are gonna do this yourself. Check everything with a finetooth comb and take your time. If you're thinking of having a local shop do it, you would be better off buying a crate motor and stuffing it in. Most shops overlook the obvious, let alone the details. Your valvetrain has taken a huge beating. Don't, Don't, Don't forget to change lifters. It would suck to get everything back together only to have a bad lifter, remember, that requires removing the heads, again, right after you just got it back together. Take your time, good luck, Let us know how it goes.
Thread Starter
On The Tree
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Lol alright fine my bad sensor story was complete bullshit lol. Think my rockers really got beat to death? I should go over everything with a fine tooth comb thats good advice, im in the process 
. So far all i did with my rockers is compare the ones on the bent valves to the known good ones and the play or lack of in all directions seems comparable, the rockers arent bent and have no signs of damage I dont think, ill look againe extreamly carefully but is there some good test to determine there mechanical capability? I really dont want to spend the money if I dont have to, but I will if its necessary. Thanks
. So far all i did with my rockers is compare the ones on the bent valves to the known good ones and the play or lack of in all directions seems comparable, the rockers arent bent and have no signs of damage I dont think, ill look againe extreamly carefully but is there some good test to determine there mechanical capability? I really dont want to spend the money if I dont have to, but I will if its necessary. Thanks 