[Eldi Z]

Are the ring gaps proven to be different between the engines?

Everyone is talking about the tight ring gaps inside the LT1 pistons and the danger of them butting in heated situations, but I have not read about this data for LT4 engines.

Clearly the lower compression together with Forged material helps longevity and handling more boost and heat on LT4s, but if the problem remains the tight ring gaps...then what?

[Joshinator99]

Originally Posted by Eldi Z

Are the ring gaps proven to be different between the engines?

Everyone is talking about the tight ring gaps inside the LT1 pistons and the danger of them butting in heated situations, but I have not read about this data for LT4 engines.

Clearly the lower compression together with Forged material helps longevity and handling more boost and heat on LT4s, but if the problem remains the tight ring gaps...then what?

Given that LT4 short blocks seem to handle ~900 WHP pretty routinely, I suspect it’s not an issue. At this point we have a decade of LT4 data and it takes a pretty serious build (or a terrible fueling & tune issue lol) to smoke them.

[Eldi Z]

OK, but did someone actually check the LT4 ring gaps for tighness?
I ask this, because everyone is talking about the LT1s as this being the main weak spot. Maybe this is not it?
Could it be that 1.3 points higher compression by itself cause the LT1s to blow easier?

Has anyone actually compared the % of destroyed LT1s on boost, Vs. LT4s tuned to 900 WHP, while their stock 93 specs are ~ 560-570 WHP?

[Joshinator99]

Originally Posted by Eldi Z

OK, but did someone actually check the LT4 ring gaps for tighness?
I ask this, because everyone is talking about the LT1s as this being the main weak spot. Maybe this is not it?
Could it be that 1.3 points higher compression by itself cause the LT1s to blow easier?

Has anyone actually compared the % of destroyed LT1s on boost, Vs. LT4s tuned to 900 WHP, while their stock 93 specs are ~ 560-570 WHP?

We know the LT1 rings are too tight for boost because multiple guys have chimed in after measuring them. I don’t remember the exact numbers off hand but I remember them being 75% tighter than the gaps on my forged pistons if memory serves…!

The ring gaps are not the only reason stock bottom end LT1s die. The higher compression, like you mentioned, does require more octane to prevent knock… so when guys push boost with pump gas or non-direct port meth they usually build heat in the chamber, exposing the tight ring gaps and breaking ring lands…or just general destruction from excessive knock. Take your pick. Either way the LT4 does not have those problems unless someone screws up their build.

TLDR; build your car depending on what you can get for fuel. If you’re stuck with pump gas, lower your compression ratio. And E85 is a godsend for boosting SBE LT1s since you get both high octane AND pulling heat out of the combustion chamber…oh, and E is great for all boosted engines for that matter.

[Eldi Z]

Thanks Josh for a comprehensive reply.
Well, I recently finished my build: LT4 1700 unit on the LT1 (17' SS-1LE). Fueling and charge cooling (+ Aux Resevoir) is LT4 End-to-End, Pulleyed down the lower Balancer ring (ATI Dampener) to 7.2" to keep boost levels to a reasonable level (expected ~ 7.5-8 psi, but did not yet log / measure). Stock Balancer ring is 8", usually results in ~ 9.5-10 PSI...Colder spark plugs (LTR6) gapped 0.035 instead of the OEM LTR5 heat gapped at 0.041. The rest remains bone stock. Unfortunatley, fuel is 93 pump...

[Joshinator99]

Originally Posted by Eldi Z

Thanks Josh for a comprehensive reply.
Well, I recently finished my build: LT4 1700 unit on the LT1 (17' SS-1LE). Fueling and charge cooling (+ Aux Resevoir) is LT4 End-to-End, Pulleyed down the lower Balancer ring (ATI Dampener) to 7.2" to keep boost levels to a reasonable level (expected ~ 7.5-8 psi, but did not yet log / measure). Stock Balancer ring is 8", usually results in ~ 9.5-10 PSI...Colder spark plugs (LTR6) gapped 0.035 instead of the OEM LTR5 heat gapped at 0.041. The rest remains bone stock. Unfortunatley, fuel is 93 pump...

Smart move getting the boost number down. At 7-8 PSI on 93 you should be OK and LT4 fueling can drive that no problem.

[Megahurtz]

Originally Posted by Eldi Z

Are the ring gaps proven to be different between the engines?

Everyone is talking about the tight ring gaps inside the LT1 pistons and the danger of them butting in heated situations, but I have not read about this data for LT4 engines.

Clearly the lower compression together with Forged material helps longevity and handling more boost and heat on LT4s, but if the problem remains the tight ring gaps...then what?

The LT1 pistons are not forged like the LT4's. Typically on boosted applications the rings are moved further down the side of the piston so they are further away from the combustion. The LT1's we're not designed with this in mind so if things get too hot the rings will expand and start some level of damage or break. Compression on the LT1 is higher as well.

For these reasons, you need to be careful with how much boost and timing you run on a stock piston LT1, especially on 93 octane. If you can run Ethanol and/or meth, you can push it a little harder as it will remove more heat from the combustion events.

[KingLT1]

Originally Posted by Joshinator99

Smart move getting the boost number down. At 7-8 PSI on 93 you should be OK and LT4 fueling can drive that no problem.

You still have to very aggressive with the IAT vs spark retard table because the engine won't take much timing once it's hot. You are looking at a massive difference from cold (meaning first start and warmed up) dyno pull vs being heat soaked from driving dyno pull. I don't know how many times I have said this, and it falls on deaf ears. That 570whp dyno pull is a cold pull. Not a realistic real-world number. 480-520whp is realistic safe numbers for a LT1 with 7-8psi on 93 when hot. Now switch to a E50 blend and it will make consistently 570-600whp in almost any conditions.

I don't know about you, but I would rather have a setup that can make sustained power in various conditions, vs a setup that is extremely reliant on perfect conditions to make power.

A lot of shops and companies are not going to admit this because they would sell a lot less parts. How many less supercharger kits would a company sell if they were truthful and said: 93 octane will work but not recommended. It's recommended to upgrade fuel system and run a E50 blend minimum or race fuel for the best and most reliable results.

[Eldi Z]

Yes, real world situations are different to Dyno pulls clearly. On the other hand, so many tuners stand with their custromers, after installing / tuning supercharged spplications on their LT1s.
They walk them through and usually customers come back for addtioonal upgrades from time-to-time, so they can follow up in time.
Lets hear these Real-World scenarios from professionals who tuned and tune these LT1s daily on all fuels and boost combinations possible, like Ted J @ JRE, Andy M @ ADM, Mike C @ Elite (Vengeance), Howard T @ Redline, Jeremy @ PPC, Pat G@ Guerra, Ricky Clarke, Justin White, Jeremy F @Fasterproms, Doug @ ECS and so many others....
Ask yourself, would all of them + all the aftermarket kit makers: Edelbrock, Magnuson, Whipple, ATI, Vortec not go out of business if so many of their LT1 engine'd custmers would break them on 93 pump gas?... I did not even mention the Californian crowd who use 91 pump on these platforms.

[18.2SS.1LE]

I'm actually surprised I didn't kill any pistons when I originally got it back from CSP. While having Jannetty retune it, we had to stop until I put a JMS and LT4 injectors in because we were way out of fuel past 7ms. I am curious what kind of timing and AFR people are hurting these at, from my experience they have been stronger than the internet says.

[RobZL1]

I'm surprised you had issues with the tune. It seems like Andrew knows what he's doing from all I've seen. Maybe the other guy in the shop tuned yours?

[Joshinator99]

Originally Posted by KingLT1

You still have to very aggressive with the IAT vs spark retard table because the engine won't take much timing once it's hot. You are looking at a massive difference from cold (meaning first start and warmed up) dyno pull vs being heat soaked from driving dyno pull. I don't know how many times I have said this, and it falls on deaf ears. That 570whp dyno pull is a cold pull. Not a realistic real-world number. 480-520whp is realistic safe numbers for a LT1 with 7-8psi on 93 when hot. Now switch to a E50 blend and it will make consistently 570-600whp in almost any conditions.

I don't know about you, but I would rather have a setup that can make sustained power in various conditions, vs a setup that is extremely reliant on perfect conditions to make power.

A lot of shops and companies are not going to admit this because they would sell a lot less parts. How many less supercharger kits would a company sell if they were truthful and said: 93 octane will work but not recommended. It's recommended to upgrade fuel system and run a E50 blend minimum or race fuel for the best and most reliable results.

100% agree King (I know you know that haha)! I’ve been an E user for a long time now… hope the Feds don’t take that statement the wrong way…

I think the point here is you CAN supercharge an LT1 at low boost and 93 octane. It’s just not even close to optimum as King mentioned, you’ll leave power on the table, and the risk of SBE damage is higher VS running at least some E in the fueling. But some people can’t/won’t run E so I guess those are the risks involved.

[Eldi Z]

This + depends a lot on how you drive (constant WOTs, even if oil is still cold, Long WOT pulls over 15 seconds in 90+ ambient, Etc.) where you dirve it (Track, Drag, AutoX).
You see bone stock engines fail like this.

[Eldi Z]

Originally Posted by 18.2SS.1LE

I'm actually surprised I didn't kill any pistons when I originally got it back from CSP. While having Jannetty retune it, we had to stop until I put a JMS and LT4 injectors in because we were way out of fuel past 7ms. I am curious what kind of timing and AFR people are hurting these at, from my experience they have been stronger than the internet says.

This is all on a SBE?
Which Octane? E?
How many miles since you put on the Procharger?