Ls/Lt Hybrid
Thread Starter
Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
Ls/Lt Hybrid Does anyone have some practical insight on piston selection for the Gen III with LT heads? The amount of information discrepancies between piston manufacturers is off the charts.
The basics are valve layout is reversed from a LS design to a LT design…as I’m sure you’re aware. To add to this, the valves in the LT head are canted, so you’ll need dedicated valve reliefs that are cut to match the canted valve layout…which means the reliefs are canted also. I would have to believe that this will be a custom built piston unless you’re going to start with a flattop piston set without reliefs, and then flycut your own reliefs…which is what I would do in this situation. I prolly haven’t told you anything you don’t know here. You can buy the cutters from Lindy which is where I get mine, very reasonably. Just give him your valve sizes and he will have you a set made up in a jiffy. This would be much cheaper than having a custom set built, and will take 8 weeks minimum.
Thread Starter
Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
Thanks for the info! I was looking at those cutters yesterday thinking that might have to be my direction. I’ll start on the hunt for some flattops. Would you flycut a set of the Gen V DI “flattop” pistons or just move to standard Gen III/IV flattop?
It’s an oddball combination for sure, but I’ve got a great set of complete CNC heads and a block that is all prepped. I figured I might as well use what I have and save a little cost since I have to source everything anyway.
Thanks again!!
It’s an oddball combination for sure, but I’ve got a great set of complete CNC heads and a block that is all prepped. I figured I might as well use what I have and save a little cost since I have to source everything anyway.
Thanks again!!
Thanks for the info! I was looking at those cutters yesterday thinking that might have to be my direction. I’ll start on the hunt for some flattops. Would you flycut a set of the Gen V DI “flattop” pistons or just move to standard Gen III/IV flattop?
It’s an oddball combination for sure, but I’ve got a great set of complete CNC heads and a block that is all prepped. I figured I might as well use what I have and save a little cost since I have to source everything anyway.
Thanks again!!
It’s an oddball combination for sure, but I’ve got a great set of complete CNC heads and a block that is all prepped. I figured I might as well use what I have and save a little cost since I have to source everything anyway.
Thanks again!!
Thread Starter
Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
Definitely going to use port injection. Still undecided what manifold to use, leaning towards something straightforward like a Holley Lo-Ram or a BTR Trinity. DI will be plugged off with an ICT kit as opposed to welding and machine work - not the ideal way, but I don’t have the skills to tackle it properly. Frankly, I’m more or less winging (with some due diligence) through the whole thing…just wait until I get to the part where I attempt to attach this absolutely wrong turbo I have sitting here (I’ve got some unconventional ideas for that too)
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo Thread Starter
Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
The advantage for me is I have a completely machined and prepped block and I acquired a set of cnc ported lt heads (complete and in perfect shape) with some miscellaneous other parts that I was after at the time. They ended up being nearly free.
I have to get all the other components anyway so I thought I’d save the cost of some heads and use what I have.
I have to get all the other components anyway so I thought I’d save the cost of some heads and use what I have.
Thread Starter
Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
I haven’t had a chance to call any manufacturers yet on this, but am I overthinking this one?
Is there any reason I can’t just put in an aftermarket set of actual gen V -10cc pistons from the get go? Or maybe a set of gen III/IV at a -10cc with the dish giving the valve clearance? Ballparking it seems the compression ought to be in a decent area with a 6.125 rod and a 4” crank. Little over a 10:1 or so
Do the Gen V dish pistons still have a pronounced direct injection “splash pad” or would it be minimal enough to not have a significant effect on the quench?
If it was still the stock bore instead of 3.800, I’d use a couple singles to experiment on. After a couple oversized, it starts to not get far off just saving up a little more for custom ones if it didn’t work.
Is there any reason I can’t just put in an aftermarket set of actual gen V -10cc pistons from the get go? Or maybe a set of gen III/IV at a -10cc with the dish giving the valve clearance? Ballparking it seems the compression ought to be in a decent area with a 6.125 rod and a 4” crank. Little over a 10:1 or so
Do the Gen V dish pistons still have a pronounced direct injection “splash pad” or would it be minimal enough to not have a significant effect on the quench?
If it was still the stock bore instead of 3.800, I’d use a couple singles to experiment on. After a couple oversized, it starts to not get far off just saving up a little more for custom ones if it didn’t work.
How far along is this? Headers will be an issue too. I have seen some swap cams out there, so the project exists. I'm in for results, have been thinking very hard on doing same build maybe on my LSX block.
Thread Starter
Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
I’m still a ways out, but have a pretty clear path now. If I wasn’t using a 4” crank and 6.125 rods, there is a lot more options for pistons.
Cams aren’t too tough to track down as there’s several places offering them.
I’m soon to start the dowel drill out, which is my only wildcard without buying the expensive jig kit. From what I’ve come across digging around is others have been far less precise than I had in mind and it’s worked just fine.
Cams aren’t too tough to track down as there’s several places offering them.
I’m soon to start the dowel drill out, which is my only wildcard without buying the expensive jig kit. From what I’ve come across digging around is others have been far less precise than I had in mind and it’s worked just fine.