Hey guys,

So I recently broke the ring land on the #7 piston of my ls3. The engine starting making a knocking noise after a long pull (I believe meth stopped spraying and it detonated) so I parked it and pulled the engine. Setup is stock ls3, tsp headers, borla exhaust, AA vortec v3si w/3.6 pulley. I believe 12-13 psi. Also added an alky control kit with dual nozzle when I retuned for 3.6 pulley. Probably around 650 wheel.

Anyhow, I'm stumped. Piston is missing a.chuck, it flew out the exhaust valve and didnt damage the cylinder or head. Rod bearings are good as well. I was thinking of slapping another oem piston in there and putting it back together with ARP rod bolts, head studs, morel lifters, new pushrods, btr springs, etc. Is there any reason why I shouldn't do this? Trying to save some cash right now as I have newborn and the wife isn't working.

If this is.a horrible idea can you recommend a good set of rods and pistons, the options are mind boggling. Also I don't plan on ever going over 700whp. I still haven't figured out the knocking noise, lifters look good, pushrods look good, valves look good, never lost oil pressure. Would this broken ring land cause a knocking sound? Engine has 34k, 15k boosted.

Thanks in advance for any advice or help

Doug

 

A piston with that little bit missing isn't going to cause a knock. I'd tear is down far enough to check all of the bearings. That cylinder wall looks good from here. Might get lucky and put it back together inexpensively. You don't need to go crazy with forged parts at your power level.

 

I agree with old motorhead that a knock isn’t a good sign, unless you are saying that you heard it knock when the ring land broke. If it still had a knock when you shut it down, that could be from that piston rocking a bit in the bore, but I doubt that it would make that loud of a knock.
The only way to know for sure is to pull the engine down completely.
That bearing looks a little iffy, as does the crank journal. What kind of oil did you use in it?
But, if there are no detectable scores on any of the rod or main journals (something you can feel with your fingernail, then with just a polish job on the crank, you should be fine to reuse the stock crank.
If none of the bearings spun in the rods, then you can reuse them too.
If that bore is good, I would buy a stock piston, hone the block and put new rings in every bore and check the end gap, and maybe open the top ring gap up a tad on all of the bores to prevent a ring hanging up and tearing the ringland like that again.
Since you have it pulled down, if you’re budget allows, I would install a decent blower cam and change the springs to match the cam. That way you’ll make more power with less boost with a lower DCR and lower IATs as well.
For the rebuild, just use LS9 gaskets and ARP bolts, which are cheaper than the studs and will give you more than enough clamping force for what you’re doing.
In the end, you’ll end up with a better, more powerful motor than will probably last you at that power level until the newborn can takeover the wheel.

 

Hey guys,

Thanks for the responses. I have moved the engine into my "clean room" and started tearing it down. Here is the worst of the rod bearings. Cylinder #2, I can slightly feel the grooves in this bearing but nothing on the crank. I believe I found the source of the tick/knock. The chain tensioner has come apart completely. It's a stock tensioner, so I will go back with the ls2 style. Can someone confirm a completely busted tensioner will cause alot of noise? I will try to post the video from before teardown. If it's not the tensioner I don't know what else it could be.

Thanks,
Doug

 

Hey guys,

Thanks for the responses. I have moved the engine into my "clean room" and started tearing it down. Here is the worst of the rod bearings. Cylinder #2, I can slightly feel the grooves in this bearing but nothing on the crank. I believe I found the source of the tick/knock. The chain tensioner has come apart completely. It's a stock tensioner, so I will go back with the ls2 style. Can someone confirm a completely busted tensioner will cause alot of noise? I will try to post the video from before teardown. If it's not the tensioner I don't know what else it could be.

Thanks,
Doug

 

If all the bearings look good and you can't find any other issues, then its most likely the broken chain tensioner causing the knock.

Are you going to go with a larger piston ring gap before you put the engine back together?

 

I'm thinking about it, never done it before. At this point I have car parts spread out all over my house. I want to get this thing back together ASAP, I hate clutter.

 

get a new piston and open your ring gaps on all the pistons. slap back together and hope for no knock.

 

If none of your bearings were spun, I think that the knock was just the chunk of the piston being banged against the head before it finally exited the exhaust valve. That or the broken tensioner.
BTW: make sure to replace the spring timing chain tensioner with a LS2 style damper.

 

The knock was there all the way up untill I parked it in the garage. The tensioner was blown to pieces and the chain was super loose. I believe I should I install new bearings in this engine. They aren't horrible, but there is some trash in a few of them. The crank has two spots that catch your nail. Going to get pricing tomorrow to regrind/polish the crank and install bearings. Also going to start looking for some rods and pistons they can install at the same time. I would be livid if one of the other 7 pistons let's loose after all this effort.

 

Wouldn't hurt to cut open your oil filter and see what it shows. Also, check the small ends of the connecting rods for excessive play. Particularly the one with the piece missing. I really can't see where a loose timing chain would cause any kind of knock.

 

I think that'll polish no problem. You can probably find a drop in set of pistons.. I know they're pretty common on C7/LT1's, not sure about LS's but surely someone has them.

If it were mine I'd throw a stock piston in and go with it if that's the only issue but I'm cheap like that and have had good luck with stock stuff.

Obviously, if there's a bearing issue then that's #1 priority

First hit on google:
https://www.texas-speed.com/p-9331-t...ls3-crank.aspx

 

All good above. But, the knock isn't coming from the timing chain problem. My first LS3 (2008 Vette) had the tensioner in pieces when I went to change the cam. No noises or knocks what so ever. I've had several gen 1 small blocks with timing chains with all kinds of slack. Again, no noises. If the timing chain makes noise, it's only going to do it once when it breaks The timing chain is pretty spindly. It's not going to make noise for very long before breakage.

 

Thanks everyone for the input. I'm going to drop the block off at the machine shop and have them go through it. I hate spending this kind of money on a car I barely drive, but it's been paid off for years and only has 34k. The cheap man pay twice and I feel like that's exactly what would happen if I patch this thing together.

 

You're a wise man. Let us know what was causing the knock. Machine shop should find it pretty quick.

 

Ok guys, machinist looked at the block, crank and cam. All is good. Bored it .005 over. Went ahead and ordered some DSS fx pistons off summit. I'm going to use the stock rods with ARP bolts. Pistons, rings, and rod bolts are $850. After I placed the order I found a combo on Texas speed. DSS sx pistons and eagle h beams for $1000. I'm going to be at the same power level as before (around 700 wheel). Would you go with the better pistons, stock rods/arps or the cheaper piston + eagle rod?

 

If it’s apart why not spend the money on good parts that will last and be reliable? Cheaper to do it once.

 

Got a decent deal on the cp carillos and Texas speed h-beams today. It's too bad you can see these bad *** parts once they are together

 

Hopefully you CAN'T see them...

 

I see what you did there!