[LibertyHill]

Great info here and I have a couple points to emphasize. Let's not forget the weak cast pistons that can drop a ring land at 650-700whp. Unless you are planning to go for the next 120-150 HP with the insane cost of the next-stage fuel upgrade why a larger blower? Any additional high RPM power potential will be at the expense of some bottom-end power anyway, and any blower is additional weight up front upsetting handling balance. LT4 is lightest. Very happy with mine!

[KingLT1]

Originally Posted by LibertyHill

Great info here and I have a couple points to emphasize. Let's not forget the weak cast pistons that can drop a ring land at 650-700whp. Unless you are planning to go for the next 120-150 HP with the insane cost of the next-stage fuel upgrade why a larger blower? Any additional high RPM power potential will be at the expense of some bottom-end power anyway, and any blower is additional weight up front upsetting handling balance. LT4 is lightest. Very happy with mine!

The stock eutectic pistons are not as weak as lead on to be...there are some LT1's in the wild making 760+whp with the stock engine and being daily driven. The key is to proper tuning. There are not many shops out there that can tune a Direct Injected engine correctly. Using traditional wide band AFR readings is not the correct approach on these motors...and that is the difference between making a high HP LT1 live or burn up.

[DFW1LE]

Originally Posted by KingLT1

The stock eutectic pistons are not as weak as lead on to be...there are some LT1's in the wild making 760+whp with the stock engine and being daily driven. The key is to proper tuning. There are not many shops out there that can tune a Direct Injected engine correctly. Using traditional wide band AFR readings is not the correct approach on these motors...and that is the difference between making a high HP LT1 live or burn up.

What about the ring gap at high boost? Also the wrist pins seem to be another source of failures.

[KingLT1]

Originally Posted by DFW1LE

What about the ring gap at high boost? Also the wrist pins seem to be another source of failures.

Talk to Ted Jenetty...he has a customer that is making 760whp on the stock LT1. Daily drives it for almost 2 years. Tuning is critical at high HP levels...detonation can cause a lot of failures that get blamed on the parts not being able to handle the power.

[DFW1LE]

Originally Posted by KingLT1

Talk to Ted Jenetty...he has a customer that is making 760whp on the stock LT1. Daily drives it for almost 2 years. Tuning is critical at high HP levels...detonation can cause a lot of failures that get blamed on the parts not being able to handle the power.

Of course a good tune is critical at any level if you want long term longevity.

[LibertyHill]

Originally Posted by KingLT1

The stock eutectic pistons are not as weak as lead on to be...there are some LT1's in the wild making 760+whp with the stock engine and being daily driven. The key is to proper tuning. There are not many shops out there that can tune a Direct Injected engine correctly. Using traditional wide band AFR readings is not the correct approach on these motors...and that is the difference between making a high HP LT1 live or burn up.

What does that leave? EGT? Can you expand more on this?

[Sol4rfl4re]

Originally Posted by LibertyHill

What does that leave? EGT? Can you expand more on this?

Lambda.

[KingLT1]

That and paying attention to injector pulse width is critical. I am sure there is more but combustion chamber events are very critical. The good tuners are not going to give up all their tricks being the money and time they have spent to obtain this knowledge. DI is a complete different animal to tune.

[wnta1ss]

Originally Posted by KingLT1

The stock eutectic pistons are not as weak as lead on to be...there are some LT1's in the wild making 760+whp with the stock engine and being daily driven. The key is to proper tuning. There are not many shops out there that can tune a Direct Injected engine correctly. Using traditional wide band AFR readings is not the correct approach on these motors...and that is the difference between making a high HP LT1 live or burn up.

Obviously tuning is important, but daily driving is not where the ring/piston problem tends to happen, it's usually reported to be long runs under boost. Long run info is from the Procharger guy that posts on here. I believe what he is saying is, even with a good tune, if you make long runs at full boost/load (further than a 1/4 mile), the heat builds up and combined with the tight ring gaps the LT1 often has, it could break the pistons.

[ADM PERFORMANCE]

Factory LT1 Ring gap spec per Gm production line -

•Piston Ring End Gap – First Compression Ring – Measured in Cylinder Bore – Production

0.009–0.0153 in


•Piston Ring End Gap – Second Compression Ring – Measured in Cylinder Bore – Production

0.0126–0.0248 in


2015-2018 LT4 ENGINE


•Piston Ring End Gap – First Compression Ring – Measured in Cylinder Bore – Production

0.009–0.0153 in


•Piston Ring End Gap – Second Compression Ring – Measured in Cylinder Bore – Production

0.0126–0.0248 in

The problem is Gm tolerances can be way to tight if they fall on the tight side . Many of the Gm LT engines we have taken apart have this huge variation PISTON TO PISTON .

So what Gm's says is acceptable will not fly in my book or any other known engine builders book.


LT4 PISTON VERSUS LT1 PISTON

If you compare the LT1 Piston ring grooves to a LT4 Production piston ring grooves you will see that the top ring land and second ring land on the LT4 piston has a steel ring cast into the piston thus making it stronger than the LT1 Piston, Meaning that if the rings do but up under expansion or flutter the land will take the abuse much better than the thin weak ring land of the lt1 piston.Forged aluminum pistons (1) with internal ribs, graphite coated skirt (3) and full floating piston pins. Piston and pin services as an assembly.

These are all documented data points that my shop and others have proven, none of this is made up.

[ADM PERFORMANCE]

Explained: Direct Injection Piston Design and Tuning Theories

http://www.hotrod.com/articles/expla...ning-theories/

[KingLT1]

Originally Posted by wnta1ss

Obviously tuning is important, but daily driving is not where the ring/piston problem tends to happen, it's usually reported to be long runs under boost. Long run info is from the Procharger guy that posts on here. I believe what he is saying is, even with a good tune, if you make long runs at full boost/load (further than a 1/4 mile), the heat builds up and combined with the tight ring gaps the LT1 often has, it could break the pistons.

I know daily driving is not what causes the issue. That car I mentioned is not driven easy. Been making 760+whp for 2 years and driven hard while being a daily driver. Is that more clear? I get that GM sets the ring gaps tight on the LT1 just as they did on LS engines. They will still handle lower amounts of boost just fine with good tuning. Anyhow, I have no intentions of making that kind of power on the SBE. I would do forged slugs for sure. My point was that there are stock LT1's out there making big power and surviving. I am not advocating everybody should try it.

[LibertyHill]

Still all good info that favors staying at the 600HP power level. Next stage is double the cost. So lets just say LT1 power boosts cost about $50/HP. Strange we haven't heard of more failures on the dyno.

Would anyone agree that as more and more miles are accrued on a SC build the rings will continually wear, marginally increasing the ring gap and decreasing the risk of ring bind on a long hard pull?

[1968ss350]

On a MUSTANG Dyno My stock Maggie kit made 508 RWHP and 491 rwtrq... He told me it's a conservative dyno and a bit of a heartbreaker. This is after a CUSTOM tune. Stock Magnuson tune made like 470 RWHP