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Old 06-12-2013, 01:22 PM   #1
Fiftydriver

 
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Stock LSX376-B15, anyway to increase compression ratio

Hey guys,

I have been reseaching a somewhat affordable way to up the power in my 2010 camaro. Working on the fuel system upgrades now and will be pretty much ready for the final engine upgrade.

I have been looking really hard at the new LSX376-B15 long block but the only thing that is really scaring me away from this is the 9:1 compression. My car is a 100% street car, no strip time at all so street manners are far more important to me then very top end power. I have been told that the 9:1 compression will result in a very sluggish feel when out of boost. Having been driving my L99 with the Maggie for a while, I love the instant grunt with that combo but the L99 has the higher 10.4:1 compression which makes it feel very stout on the street even out of boost.

Back to the LSX376-B15 long block, is there anyway to raise the compression ratio near 10:1 without replacing the pistons, such as shaving the heads to decrease combustion chamber volume or go with thinner head gaskets.

I realize there may be issues created with valve clearance and thinner head gaskets may not be a great idea for running 12-15 lbs of boost.

Anyway, just looking for any experience, love the idea of the LSX376-B15 being relatively affordable, fully forged and capable of handling at least 15 lbs of boost. Not only that, you can get one shipped today!!! No wait.

Just looking for advice.

Thanks for your time
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Old 06-12-2013, 01:46 PM   #2
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I was facing the same issue on my build - especially as I wanted to keep my maggie - the low compression doesn't really fit the bill for this sort of blower. That's why I'm building my engine now using a LSA block, shooting for 14-15 lbs of boost with around 10.1-10.4 of compression.

The LSA block will withstand far more power than a Maggie can deliver, is lighter and available as well ...

Sorry for not answering your question, I didn't even check the options of reducing cr on the LSX... the LSA was the obvious solution for me!
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Old 06-12-2013, 01:57 PM   #3
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Quote:
Originally Posted by Fiftydriver View Post
Back to the LSX376-B15 long block, is there anyway to raise the compression ratio near 10:1 without replacing the pistons, such as shaving the heads to decrease combustion chamber volume or go with thinner head gaskets.
You would need to take out roughly 10cc out of the chamber to get up to 10:1, which is kind of a lot. By the time you do that, considering the labor, machining costs, new gaskets and bolts, etc you may want to consider a custom LS3 shortblock. I just quoted a gentleman looking at a 416ci ERL longblock for 12psi and it was pretty comparable to the LSX376.
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Old 06-12-2013, 04:13 PM   #4
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You could do a forged (with nicer pistons) block from a good vendor for the same or less and not worry about this.
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Old 06-12-2013, 04:19 PM   #5
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Isn't the LSx376 an iron block? Low compression, heavy assed block (totally unnecessary if a TVS2300 is your power adder), powdered metal connecting rods.....it just doesn't add up to me vs building an LS3 block based motor like it needs to be built for the job you're wanting to do. If the motor you have now is in good shape, it's worth quite a bit. Get you a motor built, that EXACTLY matches (no compromises) what you're trying to accomplish. It won't cost any more and you'll be much happier with the outcome.
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Old 06-12-2013, 04:45 PM   #6
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Exactly. Look at the options from livernois/TSP. I would just call Livernois and order a nice forged ls3 setup for $5k or so, and be happy. Sell stock motor for $3500 or so.
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Old 06-12-2013, 05:19 PM   #7
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Quote:
Originally Posted by old motorhead View Post
Isn't the LSx376 an iron block? Low compression, heavy assed block (totally unnecessary if a TVS2300 is your power adder), powdered metal connecting rods.....it just doesn't add up to me vs building an LS3 block based motor like it needs to be built for the job you're wanting to do. If the motor you have now is in good shape, it's worth quite a bit. Get you a motor built, that EXACTLY matches (no compromises) what you're trying to accomplish. It won't cost any more and you'll be much happier with the outcome.
Yes its around 100 lbs heavier then the LS3 but I was looking simply for longevity more then anything.

The LSX376-B15 is fully forged, forged pistons, forged crank. The one you are thinking of is not labeled as the LSX376-B8 designed for lower boost levels.

Just checked with one very good shop and was quoted $14K for a 416 forged long block. Now that did not include the core charge discount and this was a top of the line engine with best of the best parts used throughout. Well worth the price tag I am sure, just not sure if I could remain married if I dropped this amount of cash on an engine!!! Plus add in the added cost for very high end fuel supply system to feed it and installation cost of the engine, I would be pushing $20K very quickly and thats more then I want to spend.

Just figured that with the $7100-$7300 cost of the LSX376-B15 long block, throw on my Maggie off my current motor, drop $1000 on fuel pump upgrades and figure $2500-$3000 for complete installation of motor and I would be around $11-$12K with the ability to hit that 700-750 rwhp range safely and comfortably.........

If the LSX376-B15 had a 10:1 to 10.4:1 compression ratio, I would jump all over it but just worried how the lower comp at 9:1 will feel for street use???? And again, as mentioned, I can order one today and it will ship tomorrow.
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Old 06-12-2013, 05:35 PM   #8
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You are correct that the cr will hurt you a ton with the maggie.We have helped build some of the highest hp maggie builds to date and will gladly take care of your build as well as taking your stock motor in trade.Give me a call and ill be glad to help you with your complete build.
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Old 06-12-2013, 06:10 PM   #9
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Quote:
Originally Posted by Fiftydriver View Post
Yes its around 100 lbs heavier then the LS3 but I was looking simply for longevity more then anything.

The LSX376-B15 is fully forged, forged pistons, forged crank. The one you are thinking of is not labeled as the LSX376-B8 designed for lower boost levels.

Just checked with one very good shop and was quoted $14K for a 416 forged long block. Now that did not include the core charge discount and this was a top of the line engine with best of the best parts used throughout. Well worth the price tag I am sure, just not sure if I could remain married if I dropped this amount of cash on an engine!!! Plus add in the added cost for very high end fuel supply system to feed it and installation cost of the engine, I would be pushing $20K very quickly and thats more then I want to spend.

Just figured that with the $7100-$7300 cost of the LSX376-B15 long block, throw on my Maggie off my current motor, drop $1000 on fuel pump upgrades and figure $2500-$3000 for complete installation of motor and I would be around $11-$12K with the ability to hit that 700-750 rwhp range safely and comfortably.........

If the LSX376-B15 had a 10:1 to 10.4:1 compression ratio, I would jump all over it but just worried how the lower comp at 9:1 will feel for street use???? And again, as mentioned, I can order one today and it will ship tomorrow.
Did you look into forging your ls3 that you currently have.
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Old 06-12-2013, 06:34 PM   #10
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There are differences in forged parts. Like pointed out, the pistons are a low quality alloy compared to most forged pistons.

$14k is crazy. I paid less than that for a top of the line 427.
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Old 06-12-2013, 06:36 PM   #11
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Doesn't that block still use powder metal rods which stock rod bolts?
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Old 06-12-2013, 06:56 PM   #12
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Don't change the compression. We have used this engine already
And is not a slug.

I love how these Internet engineers always seem to try
To steer people away from gm crate engines... Ask real supporting vendors
These questions and you will get real answers due to real
World experiences used everyday.

I say go Lsx and never look back...
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Old 06-12-2013, 06:59 PM   #13
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Originally Posted by JLE58 View Post
Doesn't that block still use powder metal rods which stock rod bolts?
When's the last time you broke a powder metal rod?

Let me guess, the Internet said they are no good.

Proper built/tuned engines don't break rods or fail
Bearings or pistons.
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Old 06-12-2013, 07:36 PM   #14
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Isn't there a guy on here with a Maggie blown low compression 416 that's stuck around the 600rwhp number? Isn't a forged crank a bit overkill at any hp number a Maggie is capable of? Not for a moment saying it's a bad choice. Just that I think there are better bang for the buck options out there.

Unless I read things wrong, TxSpeed has a forged long block LS3 with ported heads for around $8K. All new parts. New block, new ported heads, and your choice of custom cam. Your choice of compression ratio. You don't get a forged crank, but that isn't an issue at Maggie hp levels. If you think a forged crank is necessary, it's available for a few more bucks.

I know I'm a bit of an internet racer, but my TxSpeed long block will show up next week. It's an iron block, but it's also going in a truck. Maggie blown of course
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