Ls9 lifters in LS1?
TECH Senior Member
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From: Central Cal.
No problem G. That's a very good question. There are recommended quench ranges. Those are basically set by connecting rod type (steel/aluminum) and RPM range. Check out this article in our help center about quench and the recommended ranges.
When using your Compression Calculator (had lots of fun with this too!), to get the factory-spec LM7 compression of 9.5:1, I need to use zero deck clearance.
Yet I hear repeatedly that most LS engines have about a -.005-6 spec.
That makes a big diff when figuring quench! What's the correct answer here?
If I use -.005 deck clearance, I would need a .045 gasket to get .040 quench (middle of suggested quench range).
If I use zero deck clearance, a .040 gasket is called for to get the same quench.
Also- Should one err to the low side of the quench range (.035 out of .035-.045) or go to the high side (.045)?
Edit- your article answered the above question- Quench should be as tight as possible.
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Staging Lane
Joined: Mar 2020
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From: Mississippi
For factory .051" head gaskets you'd want the GM NAL-12498544 LS1/LS6 MLS head gaskets. For a nice compression bump and to reduce quench you could go with the .045" Trickflow by Cometic MLS TFS-30694030-045. With .045" head gaskets and 65cc 243 heads, you would be right around 10.7:1 compression with .041" quench. With the .051" head gaskets and 243 heads, you would be right around 10.5:1 compression with .046" quench. Bumping the compression up will improve power/torque across the range. Reducing the quench distance will help improve a more efficient combustion cycle and reduce the chance of knock.
Okay great so is stock ls1 lifter trays acceptable with LS7 Summit lifters? That was my real question.
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You'll want to replace the lifter trays to ensure there is no wear giving the lifters a chance to rotate in the lifter bore. Most replace with the GM Performance LS2 lifter trays (12595365). Beware of knockoff Chinese trays they can cause serious damage if the lifter rotates.
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Staging Lane
Joined: Mar 2020
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From: Mississippi
You'll want to replace the lifter trays to ensure there is no wear giving the lifters a chance to rotate in the lifter bore. Most replace with the GM Performance LS2 lifter trays (12595365). Beware of knockoff Chinese trays they can cause serious damage if the lifter rotates.
Okay great! So LS7 summit lifters with ls2 lifter trays? This is my first time taking cylinder heads off & replacing lifters that’s why I’m asking so many questions.
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From: Thibodaux LA
For factory .051" head gaskets you'd want the GM NAL-12498544 LS1/LS6 MLS head gaskets. For a nice compression bump and to reduce quench you could go with the .045" Trickflow by Cometic MLS TFS-30694030-045. With .045" head gaskets and 65cc 243 heads, you would be right around 10.7:1 compression with .041" quench. With the .051" head gaskets and 243 heads, you would be right around 10.5:1 compression with .046" quench. Bumping the compression up will improve power/torque across the range. Reducing the quench distance will help improve a more efficient combustion cycle and reduce the chance of knock.
To the op. The morel drop in lifters are good to go. Upgrade over the ls7 lifters and the morels can take the higher spring pressures
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From: Central Cal.
"LS2 lifter trays" are the current GM regular production lifter tray that was improved for LS2 and ALL OTHER CURRENT LS engine production. If you buy any genuine GM lifter trays, they will be the LS2 type.
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From: South Carolina
The Morel lifters in my LQ9 are quiet during idle (no sewing machine noise .629 lift with .660 springs), no issues with my 7000 RPM limiter setting. With the Morel's be advised they take less preload than the LS7 lifters. Morel wants .030" to .040" for an iron block alum heads. I've read Martin @Tick said .030 to .060 is fine with Morel's. I wound up with a .045" preload.
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Staging Lane
Joined: Mar 2020
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From: Mississippi
TECH Senior Member
Joined: Jun 2016
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From: Central Cal.
For our Summit LS gurus- (continuing from a previous post in this thread; this will end the hijack, I promise!)
When using your Compression Calculator (had lots of fun with this too!), to get the factory-spec LM7 compression of 9.5:1, I need to use zero deck clearance.
Yet I hear repeatedly that most LS engines have about a -.005-6 spec.
That makes a big diff when figuring quench! What's the correct answer here?
When using your Compression Calculator (had lots of fun with this too!), to get the factory-spec LM7 compression of 9.5:1, I need to use zero deck clearance.
Yet I hear repeatedly that most LS engines have about a -.005-6 spec.
That makes a big diff when figuring quench! What's the correct answer here?
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From: Ohio, Georgia, Nevada, Texas
For our Summit LS gurus- (continuing from a previous post in this thread; this will end the hijack, I promise!)
When using your Compression Calculator (had lots of fun with this too!), to get the factory-spec LM7 compression of 9.5:1, I need to use zero deck clearance.
Yet I hear repeatedly that most LS engines have about a -.005-6 spec.
That makes a big diff when figuring quench! What's the correct answer here?
When using your Compression Calculator (had lots of fun with this too!), to get the factory-spec LM7 compression of 9.5:1, I need to use zero deck clearance.
Yet I hear repeatedly that most LS engines have about a -.005-6 spec.
That makes a big diff when figuring quench! What's the correct answer here?
The answer here is the ol' "It depends". Here's what we mean. The GM compression ratio spec for the LM7 is 9.5:1. However, we know that there is a tolerance built-in for every component that determines an engine's compression ratio. Plus, with manufacturing at scale, some engines will leave with a slightly higher or lower compression than the published spec.
When we talk about performance engine building, we can better control the end results. While our Help Center lists the GM spec, once you start measuring engine components we see that reality doesn’t necessarily match the published spec. The good news is we can take steps to modify components or select components to control the desired outcome.
Similar to us recommending measuring for proper pushrod length, trying to hit a specific quench number will be the same. You’ll need to measure your deck clearance so the gasket can be matched as closely as possible.
TECH Senior Member
Joined: Jun 2016
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From: Central Cal.
G, sorry for the delayed response.
The answer here is the ol' "It depends". Here's what we mean. The GM compression ratio spec for the LM7 is 9.5:1. However, we know that there is a tolerance built-in for every component that determines an engine's compression ratio. Plus, with manufacturing at scale, some engines will leave with a slightly higher or lower compression than the published spec.
When we talk about performance engine building, we can better control the end results. While our Help Center lists the GM spec, once you start measuring engine components we see that reality doesn’t necessarily match the published spec. The good news is we can take steps to modify components or select components to control the desired outcome.
Similar to us recommending measuring for proper pushrod length, trying to hit a specific quench number will be the same. You’ll need to measure your deck clearance so the gasket can be matched as closely as possible.
The answer here is the ol' "It depends". Here's what we mean. The GM compression ratio spec for the LM7 is 9.5:1. However, we know that there is a tolerance built-in for every component that determines an engine's compression ratio. Plus, with manufacturing at scale, some engines will leave with a slightly higher or lower compression than the published spec.
When we talk about performance engine building, we can better control the end results. While our Help Center lists the GM spec, once you start measuring engine components we see that reality doesn’t necessarily match the published spec. The good news is we can take steps to modify components or select components to control the desired outcome.
Similar to us recommending measuring for proper pushrod length, trying to hit a specific quench number will be the same. You’ll need to measure your deck clearance so the gasket can be matched as closely as possible.
It sounds like a fairly wide range of tolerance on deck clearance, as would be expected in a mass production scenario. AwesomeAuto (OK name, but I liked Joe Nova better...lol) has a good common-sense answer with the .004 "common sense" plug-in number. I think I'll borrow it for future calcs, if you don't mind.
Again, thank you both for the info, especially from trusted names here!
I have run LS7 lifters with PAC springs that are 180lbs seat, 425lbs max, for 8 years and 35,000 miles. Both springs and lifters are still in there, still running fine......
