LT1 Piston failure
 

Wanted to put this out there as I didn’t see too much about it especially in this FI area. However, found several posts in the Corvette forums (after this happened).

So Prior to planning my build I searched this thread for weeks trying to decide the best route to go and to make sure I got all the right parts to to do it right and safe ... asked a lot of questions to vendors and forum members. Only 5000 miles on the engine prior to starting this build.

Decided on the below:

Whipple and changed to 3.5 pulley
HPFP, LT4 injectors, DSX lower aux
Unlocked TCM and tuned
LS3 main seal
Mighty Mouse catch can
NGK-TR7, MSD wires
Rotofab dry
TSP 1 7/8 LT

Went in for tune and at 8 psi boom (only at 576/600). Later determined cylinder 7 failed (ring land, see pic). Crushing news. Saved along time for what I got and now faced with more decisions and more money.

The shop I used and tuner are top notch, considered some of the best in my area. Don’t blame them at all. I guess just my luck. Reading all the post of people doing similar builds with no problems never considered it could happen. Right parts, reasonable boost, no problem, right... wrong.

So now what, build better, stronger or give up. Took block out and to a machine shop and after honing #7, good as new, so block is good.

Contacted GPI regarding their drop in Rod/Piston set. Great guys and not the first time they heard this. They took care of me and I ordered the set. Thanks GPI !!!

Decided on BTR stage II S/C cam kit.
Deciding on lower pulley now too.
Do not want to do meth or E85, just 93.

At this point gathering the extra parts, then will install and tune. The stock pistons are definitely the weak point in the LT1, but seems some are less forgiving. Thousands extra that wasn’t expected.

Yea reasons like this are why I'm doing my motor build first and worrying about boost later. It sucks that it happened but it sounds like like you got a plan and it'll be back better than before so good luck to ya.

It is very common for Lt1 boosted.

What is the build cost for updating an LT1 crate motor?

I'd quote stats from reputable shops at the very least when posting this kind of sweeping generalization.

Yep, just built a new motor over the winter. Those ring lands look very familiar and mine broke on 1 and 8. I was running 13 lbs when I think we broke number 1 as it pushed the front seal out at the track. Replaced that with LS3 seal not thinking it had done any damage at the point and proceeded to add another 3 lbs of boost, went to the dyno and put down 713. Went to the Camaro fest and after about 3 passes it started smoking a little as it was pushing just a little oil out of the rear seal. We replaced all the PVC hoses there with larger ones trying to evac the crank case, pulled timing to slow the car down to 10.30's and made it to the semi finals in unlimited. However my dumb ass took it to the track one more time to try and get in the 9's, cranked up the timing and pushed the rear seal out oiled down the track. That was number 8. I did a bore scope and could see the damage on those 2 cylinders and they were both down on compression. So the tear down began. I think my total cost cause I did add long tubes, probably about 9500.00.

Looking at all the photos like this I can't help but to think that the pistons really arn't the problem.... It looks like the piston rings expanded under the additional heat, butted up, and cracked the ringland. It's common knowledge to the people at performancetrucks.net that are running either the 4.8 or 5.3 that they could simply file down the piston rings a bit and the boost them to 1000rwhp (with stronger springs in the head but that's besides the point).

I wonder if it is the same thing for us (yes I know our engines are different)? I haven't heard of anyone trying this approach instead of drop in pistons... Really wish someone would if only to satisfy my curiosity.

Holy cow man that is my worst fear. I'd like to think that failures like these can happen even N/A if there's even the slightest compromise in the piston. (Flaw in the part or assembly) Perhaps this one was going to fail anyway but its demise was sped up with the boost, pressure & heat, etc.

I'd like to think with a conservative & safe tune at a reasonable power level, this motor can handle it no problem.

But with that said sure.. Anything and everything can happen.

There are a couple threads on this here. Welcome to the club, I'd say it's pretty common as well.

:facepalm: Really? I dont' think I would say it's common. Think of the masses that aren't represented here on this forum who are under 600 rwhp with a good tune and no issues. Many of us here are boosted and there honestly hasn't been many that were 600 or less that lost a motor that I can think of. Granted nothing is ever guaranteed though. Chit happens!.

Most of the failures I read about are heavily tracked LT1's making 650+.

The amount of boost is somewhat relative - 8 or 9lbs might be a limiting factor on gasoline, but we just ran 13lbs on my stock LT1 (stock intake, cam and headers) up to 5900 rpm (was making 745hp at 5900) before we pulleyed down. The pistons can take a great amount of cylinder pressure as long as there is no detonation (we were running e85 and Meth inj).

Pulleyed to 9.5 lbs and it’s very safe with 48 degrees of timing advance.

Anyone running boost should be considering Meth out of safety

I would like to see the tune file and a log of the run. I have a hard time believing that a healthy LT1 is going to let go on 8psi with correct tuning and fueling. Just because this shop is "reputable" doesn't mean a lot in 2019. In the event the tuner made a mistake, he likely won't admit it and eat the labor/parts to fix your stuff.

I just recently had my Whipple setup dyno tuned by a "reputable shop" and first thing I did was hook my hp tuners and log to check the tune. I found a lot of stuff not addressed in the tune but the fueling and timing is right. I am also on e85 which is much better then 93 with boost on these high compression engines being it is very effective at pulling heat out of the cylinders and allows more room for error. I would consider making the switch or at least run meth with 93.

sorry for your loss.

If it was lean during the pull or pulls it would be an issue depending on the timing. I had over 100 passes at 10 lbs of boost without any issues. But kept moving up the flag pole and mine failed at basically 5 more lbs of boost then yours. I did lower my compression with the new Manley pistons (10.5) from the stock compress of 11.5 if I remember correctly. Shaun at Speed Engineering basically pulled both his motors apart (C7 Z06 and Camaro SS) and regapped the rings for boost, put them both back together. The Lt1 was just not set up for a lot of boost, 8 lbs is not that much if tuned properly so maybe something else happened.

Can I ask how much hp and what psi Shaun is running on those? I really feel a regap of the rings is all that is really needed on all but the highest of hp builds... His pictures even look like the rings butted up causing this.