Buying an LS3 crate engine, looking to lower the compression without bottom end mods
Buying an LS3 crate engine, looking to lower the compression without bottom end mods So I decided on buying a crate engine, I'll be ordering it later today. I have a cam I'll be swapping in, and I'll be home porting the heads. I'll be doing some light chamber work, so depending on how much work I do, I could probably drop the compression by .2 -.3 that way. What head gaskets could I use to drop the compression? I'd like to see if I could use a GM gasket to keep cost down. I'll be running a procharger, and I'd like to make at least 600whp with it, the cam and home ported heads in this LS3. 10:1 compression would be great, stock according to GM is 10.7:1. Is this a lofty goal, or is it reasonable?
On The Tree
Joined: Jun 2015
Posts: 182
Likes: 3
From: Portland OR
I don't like spacing the head because it reduces squish, the turbulence from squish is highly beneficial.
Whether this will hurt you significantly depends on the volume of squish lost and the distance from the top of the piston to the head.
Too much gap will definitely hurt you. It becomes sort of a dead area until the piston moves down and so may promote detonation.
I don't know what the LS3 combustion chamber looks like, if it is a closed chamber you may want to swap heads to an open chamber design.
Whether this will hurt you significantly depends on the volume of squish lost and the distance from the top of the piston to the head.
Too much gap will definitely hurt you. It becomes sort of a dead area until the piston moves down and so may promote detonation.
I don't know what the LS3 combustion chamber looks like, if it is a closed chamber you may want to swap heads to an open chamber design.
So I decided on buying a crate engine, I'll be ordering it later today. I have a cam I'll be swapping in, and I'll be home porting the heads. I'll be doing some light chamber work, so depending on how much work I do, I could probably drop the compression by .2 -.3 that way. What head gaskets could I use to drop the compression? I'd like to see if I could use a GM gasket to keep cost down. I'll be running a procharger, and I'd like to make at least 600whp with it, the cam and home ported heads in this LS3. 10:1 compression would be great, stock according to GM is 10.7:1. Is this a lofty goal, or is it reasonable?
I wouldn't touch the heads.....and I wouldn't worry about compression, either. But I WOULD suggest a professionally spec'ed cam that will work, 'as is', with the stock LS3 engine.
Either that, or......
KW
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Joined: Mar 2014
Posts: 7,192
Likes: 109
From: Ohio
There is nothing limiting it to 700 HP. A stock longblock should be able to handle 1000 flywheel. Forged rotating assembly with dished pistons should easily be able to make 1200 with the right Procharger.
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Restricted User
Joined: Mar 2014
Posts: 7,192
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From: Ohio
I'm not sure where you're not seeing the boost part.
Guys have made 1200 flywheel on unported Cathedral heads that flow 20% less. I'm not sure where you're struggling with doing so on LS3 heads.
Adding boost doesn't increase CFM. You flow the exact same CFM at an increased pressure. If the heads aren't a restriction N/A, they aren't a restriction with boost.
Guys have made 1200 flywheel on unported Cathedral heads that flow 20% less. I'm not sure where you're struggling with doing so on LS3 heads.
Adding boost doesn't increase CFM. You flow the exact same CFM at an increased pressure. If the heads aren't a restriction N/A, they aren't a restriction with boost.
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Verdad Gallardo I'm not sure where you're not seeing the boost part.
Guys have made 1200 flywheel on unported Cathedral heads that flow 20% less. I'm not sure where you're struggling with doing so on LS3 heads.
Adding boost doesn't increase CFM. You flow the exact same CFM at an increased pressure. If the heads aren't a restriction N/A, they aren't a restriction with boost.
Guys have made 1200 flywheel on unported Cathedral heads that flow 20% less. I'm not sure where you're struggling with doing so on LS3 heads.
Adding boost doesn't increase CFM. You flow the exact same CFM at an increased pressure. If the heads aren't a restriction N/A, they aren't a restriction with boost.
Just that I haven't seen stock heads at 1000+ HP at the wheels.
Although, admittedly, I don't pay much attention to FI applications since I have zero plans to ever go that route.....
KW
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Joined: Mar 2014
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From: Ohio
There are probably a hundred cars making 1000+ HP on stock castings. I take it you don't frequent the Forced Induction section very often LOL.
Restricted User
Joined: Mar 2014
Posts: 7,192
Likes: 109
From: Ohio
Was with a single. Stock 6.0 block with 4" rotating assembly. Made almost 1100 wheel I think through a TH400 on gas (no E85).
My point is, if a 4-cylinder can make 1000 HP on a 300 CFM ported stock casting, then a V8 can easily make more with TWO 320 CFM stock castings. I don't understand the notion that you have to have absurd head flow numbers to make power, which exactly why I scoff at anyone who drops $2k on heads for their 400whp N/A combo. I have 1800 in my turbo setup and I've TRIPLED the power my 5.3 came with from the factory and I'm going on my 2nd year of beating the hell out of this thing on 20+ PSI.
Stop wasting money on things that don't need it. There are guys spending $2500+ to swap out their LS3 heads. I've made over 600whp with a big block that had aftermarket heads with STOCK LS3 flow numbers. You're all insane......
My point is, if a 4-cylinder can make 1000 HP on a 300 CFM ported stock casting, then a V8 can easily make more with TWO 320 CFM stock castings. I don't understand the notion that you have to have absurd head flow numbers to make power, which exactly why I scoff at anyone who drops $2k on heads for their 400whp N/A combo. I have 1800 in my turbo setup and I've TRIPLED the power my 5.3 came with from the factory and I'm going on my 2nd year of beating the hell out of this thing on 20+ PSI.
Stop wasting money on things that don't need it. There are guys spending $2500+ to swap out their LS3 heads. I've made over 600whp with a big block that had aftermarket heads with STOCK LS3 flow numbers. You're all insane......
I won't be dropping a dime in porting my heads, other than buying a porting kit to do the combustion chamber work and porting the exhaust ports. I may do intake work as well since home porting these heads aren't difficult due to the fairly large runners and they're aluminum. I'm picking up what you're putting down Joe, I just want to maximize the heads with some casting clean up and bowl work.
It seems that there's a .04 thickness difference between LS9 and LS3 gaskets, will that even register .1 in a compression drop?
It seems that there's a .04 thickness difference between LS9 and LS3 gaskets, will that even register .1 in a compression drop?
haha technically I do, but I'm not Mad Max'ing a tanker from the 2 pumps in my state to fuel my car. 93 octane only for now. I do have a meth kit in the car, but I'm not a fan of the reliability of them. The internet raves about it, but my real world use and friends don't have solid results.
I have the 3 core procharger IC for my setup.....but the stock metal IC pipes are funky looking and starting to rust inside because the SC leaked over the years and I assume the oil ate at the inside finish. So I'll be replacing the metal pipes with aluminum ones. While I'm here, i could replace the IC with a bigger one. I have a G8, and I do have plenty of room to fit a bigger IC in there, I'd just need to cut the crash bar, which I've seen done before.
Restricted User
Joined: Mar 2014
Posts: 7,192
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From: Ohio
My biggest question.
If you're building it for boost, why not start with something a little better suited? You're going to dump money into an LS3 crate only to immediately void the warranty, and your goal is well within ANY gen 4 rod equipped LS engine. Not to mention you're handicapping yourself with the compression.
It seems like you're going with the most expensive, worst way to get 700whp.
My last 3 700+ setups were all less than $5k TOTAL.
If you're building it for boost, why not start with something a little better suited? You're going to dump money into an LS3 crate only to immediately void the warranty, and your goal is well within ANY gen 4 rod equipped LS engine. Not to mention you're handicapping yourself with the compression.
It seems like you're going with the most expensive, worst way to get 700whp.
My last 3 700+ setups were all less than $5k TOTAL.