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Old 01-13-2020, 06:26 PM   #1
Eldi Z
 
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LT1 Vs. LT4 Ring Gaps

Lots of threads discuss the issues related with the apparently (too) tight factory ring gaps on the stock top rings in the LT1.

Some measurements have been performed and it was found that not all factory gaps were equal (on the LT1), but usually pretty tight (relatively).

Apart from a few clear internal differences between the LT1 and LT4, I.E. Compression Ratios, Piston and Rod material, Intake Valves material, I found no mention of the LT4's typical ring gaps.

Does anyone have practical data / actual measurements of the ring gaps in the LT4 pistons?

This data might shed some more light on the issue of "Are tight ring gaps a likely and decisive! reason for piston failures under boost"

If LT4 ring gaps are proven similar to those in the LT1, then the likelihood of this factor being THE decisive one for failure, is lower than generally thought to hold true.

Yes, I am aware that material differences between the pistons of the LT4 and LT1 are also considered a factor (they are different!), but at least if it could be proven, that the ring gaps between these engines are similar, then this factor alone (namely the tight ring gaps), could be isolated as not necessarily being the MAIN reason for piston failures on LT1s.
After-all, the LT4 is a boosted application from the factory, while the LT1 is not.

Apology for the lengthy post, but thought that such discussion might benefit the community.
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Old 01-13-2020, 06:52 PM   #2
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Gaps are determined by usage, N/A motors will always have tighter gaps. In for actual measurements though.....

General reference

Ring End Gap:
Application Top Ring Gap (Min) 2nd Ring Gap (Min) Oil Ring Rail
N/A Street .004" x Bore .005" x Bore Min .015"
N/A Race .0045" x Bore .0055" x Bore Min .015"
Turbo/Supercharged
.006" x Bore .006" x Bore Min .015"
Nitrous .007" x Bore .0065" x Bore Min .015"
Drag Race .0055" x Bore .006"x Bore Min .015"
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Old 01-24-2020, 03:02 PM   #3
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Bump for additional posts from the knowledgeable
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Old 01-24-2020, 04:54 PM   #4
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http://blog.wiseco.com/everything-yo...about-ring-gap

My second gap is larger than the first. My actual piston card called for .016. I felt that was too close and for my boosted app went with .020 top, .022 second. I felt this was heck of big for a low boost engine, but better slightly bigger than too small.

4.065 bore x HP racing of .0053 = .0215, so I'm slightly tight on the top and slightly loose on the bottom. To be honest I think they are slightly loose for my application.
I'm boost / octane limited on 11.5 CR and this is a street car so single through the gear WOT runs.
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Old 01-24-2020, 06:13 PM   #5
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Quote:
Originally Posted by oldman View Post
http://blog.wiseco.com/everything-yo...about-ring-gap

My second gap is larger than the first. My actual piston card called for .016. I felt that was too close and for my boosted app went with .020 top, .022 second. I felt this was heck of big for a low boost engine, but better slightly bigger than too small.

4.065 bore x HP racing of .0053 = .0215, so I'm slightly tight on the top and slightly loose on the bottom. To be honest I think they are slightly loose for my application.
I'm boost / octane limited on 11.5 CR and this is a street car so single through the gear WOT runs.
Thanks Oldman for this input Do you have the data for the typical stock LT4 ring gaps?
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Old 01-24-2020, 08:17 PM   #6
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No I don't, it would be interesting to know.
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2019 stage 3: Forged short block 11.5 CR, huge duration sub .600 lift Cam Motion cam, Pray Ported Heads, 3.85 pulley D1X, stage II intercooler, 2 BOVs, DSX secondary low side, DSX E85 sensor, Lingenfelter big bore 2.0, CA-offroad pipe, 60609 Borla, Lingenfelter injectors, ZL1 driveshaft and half shafts, Katech ported TB,MSD intake, BTR valvetrain.
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Old 01-25-2020, 02:02 PM   #7
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LT4 rings are not the same as LT1 rings either.
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Old 01-25-2020, 02:08 PM   #8
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Quote:
Originally Posted by Eldi Z View Post
Lots of threads discuss the issues related with the apparently (too) tight factory ring gaps on the stock top rings in the LT1.

Some measurements have been performed and it was found that not all factory gaps were equal (on the LT1), but usually pretty tight (relatively).

Apart from a few clear internal differences between the LT1 and LT4, I.E. Compression Ratios, Piston and Rod material, Intake Valves material, I found no mention of the LT4's typical ring gaps.

Does anyone have practical data / actual measurements of the ring gaps in the LT4 pistons?

This data might shed some more light on the issue of "Are tight ring gaps a likely and decisive! reason for piston failures under boost"

If LT4 ring gaps are proven similar to those in the LT1, then the likelihood of this factor being THE decisive one for failure, is lower than generally thought to hold true.

Yes, I am aware that material differences between the pistons of the LT4 and LT1 are also considered a factor (they are different!), but at least if it could be proven, that the ring gaps between these engines are similar, then this factor alone (namely the tight ring gaps), could be isolated as not necessarily being the MAIN reason for piston failures on LT1s.
After-all, the LT4 is a boosted application from the factory, while the LT1 is not.

Apology for the lengthy post, but thought that such discussion might benefit the community.
The argument that ring gaps are causing piston failures doesn't hold water IMO.

We have not had a single wimper from any of the LT engines we take from stock to well north of 750 RWHP on LT1 and 1000 RWHP on LT4 all stock long blocks.

If you remember the first Gen6 JRE Super Street Brawler we built back in early 2016, it made 742 RWHP customer drove that car very hard Daily for 3 years recently sold it to a guy in FL in perfect condition.

The buyer in FL took it to a local to him speed shop, they put meth on it and blew it up, SMH.

I got the phone call last week.
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Old 01-25-2020, 04:05 PM   #9
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My ring gaps are on the loose side for a street car IMO. My stock LT1 had forget now, but reasonable end gaps. IMO it is not a rwhp thing it is a usage thing wot blast throw the gears to 100 MPH is nothing compared to a road race in terms of heat, expansion and fatigue.
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2018 Stage 2, P1C, 4.0 pulley, Pray ported heads, Pray stage 1 blower cam, TxSpeed valvetrain, Katech ported 87mm TB, ported MSD, 1 and 7/8 headers

2019 stage 3: Forged short block 11.5 CR, huge duration sub .600 lift Cam Motion cam, Pray Ported Heads, 3.85 pulley D1X, stage II intercooler, 2 BOVs, DSX secondary low side, DSX E85 sensor, Lingenfelter big bore 2.0, CA-offroad pipe, 60609 Borla, Lingenfelter injectors, ZL1 driveshaft and half shafts, Katech ported TB,MSD intake, BTR valvetrain.
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