LS402 tear-down
02-11-2015, 08:43 PM
#1
LS402 tear-down Pulled the motor due to noise in top end. Approx 250 runs on 250 shot. Forged Motor with custom forged diamond pistons as per signature. Report from engine builder: #8 piston cracked, 4 pistons rocking so badly that they were hitting the head and top of cylinders ballooned. Block and pistons are scrap. I'm going to get a new block and pistons however I'm concerned as to why there is so much wear on pistons and block. I am pretty careful with the tuning and pulling plugs. Do members here have experience with these LS2 based strokers for big nitrous? Have they been holding up? I'm going to a custom nitrous cam from tick and was planning to run 300 shot. Any suggestions on the rebuild? Crank and rods are forged.
Last edited by CanadianEh!; 02-11-2015 at 09:59 PM.
02-12-2015, 02:39 PM
#2
Sounds like the engine was not happy.... Do you monitor pan vacuum?
250 runs is a fair amount, especially 1/4 mile runs.
A piston that cracks has too much heat into it, how are the plugs coming out? Timing mark OK?
A piston that rocks in the bore has gotten hot, and probably too much cylinder pressure.
I ran a 408 that was on 300 worth on a plate, had no issues, but that was about 50 runs and 1/8 mile.
250 runs is a fair amount, especially 1/4 mile runs.
A piston that cracks has too much heat into it, how are the plugs coming out? Timing mark OK?
A piston that rocks in the bore has gotten hot, and probably too much cylinder pressure.
I ran a 408 that was on 300 worth on a plate, had no issues, but that was about 50 runs and 1/8 mile.
02-12-2015, 02:52 PM
#4
Pulled the motor due to noise in top end. Approx 250 runs on 250 shot. Forged Motor with custom forged diamond pistons as per signature. Report from engine builder: #8 piston cracked, 4 pistons rocking so badly that they were hitting the head and top of cylinders ballooned. Block and pistons are scrap. I'm going to get a new block and pistons however I'm concerned as to why there is so much wear on pistons and block. I am pretty careful with the tuning and pulling plugs. Do members here have experience with these LS2 based strokers for big nitrous? Have they been holding up? I'm going to a custom nitrous cam from tick and was planning to run 300 shot. Any suggestions on the rebuild? Crank and rods are forged.
With a cracked slug and them rocking so bad it sounds like the tear down and refresh should have been 50-100 passes ago. An O.E. liner and a hard ring = faster wear.
Just like any build if you use good parts and quality machining/assembly along with a regular maintenance and refresh program the engine should live for a good long time.
150-200 passes, send it back for refresh(rings/bearings min.). put another 150-200 passes on it.
02-12-2015, 04:59 PM
#5
Hello, "250 runs on 250 shot" That's about or a bit past cycle life on that stuff.
With a cracked slug and them rocking so bad it sounds like the tear down and refresh should have been 50-100 passes ago. An O.E. liner and a hard ring = faster wear.
Just like any build if you use good parts and quality machining/assembly along with a regular maintenance and refresh program the engine should live for a good long time.
150-200 passes, send it back for refresh(rings/bearings min.). put another 150-200 passes on it.
With a cracked slug and them rocking so bad it sounds like the tear down and refresh should have been 50-100 passes ago. An O.E. liner and a hard ring = faster wear.
Just like any build if you use good parts and quality machining/assembly along with a regular maintenance and refresh program the engine should live for a good long time.
150-200 passes, send it back for refresh(rings/bearings min.). put another 150-200 passes on it.
02-13-2015, 11:21 AM
#6
Looking now I see you had custom Diamonds. That's something where we would like to know more about that custom piston. Like crown, skirt thicknesses, ring stack and location. Pin type and thickness
A Livernois sleeved aluminum LS block has many benefits. The ability to run a larger bore with an aftermarket ductile iron liner is a win win.
We use our own design pistons that will offer you reliability and repeat-ability pass after pass.
There are tons of options, we can help you home in on something.
Here are some pics of a Pro Series 429cui Big Bore LS we have ready to ship in the mid 9's on compression. An assembly like this is rated to 1100 Flywheel.
We can do something with a billet rod and rate the assembly for more power.
Last edited by LivernoisMotorsports; 02-13-2015 at 02:26 PM. Reason: edit question
02-13-2015, 02:18 PM
#7
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ERL Sleeves As others have said that 250 passes is a lot on a nitrous motor and you should refresh it sooner to avoid more costly issues and the fact you ran that many on a stock cast iron sleeve is proof that you did keep a good tune-up in it.
The ductile iron sleeve is not only stronger and harder for ring wear, but is also longer to reduce the piston rock at BDC. Also, ductile iron will handle a shock (such as nitrous, detonation,…) better that std. grey iron factory sleeves as they are brittle and tend to crack.
The ductile iron sleeve is not only stronger and harder for ring wear, but is also longer to reduce the piston rock at BDC. Also, ductile iron will handle a shock (such as nitrous, detonation,…) better that std. grey iron factory sleeves as they are brittle and tend to crack.