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.

 

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!!

 

This sounds like an interesting project. Im interested in the results.

 

Are you gonna use direct injection or LS style port injection? If DI, I’d go with a Gen5 style piston to begin with. You won’t have to flycut it. It’s already designed for the canted valve layout. If your staying with typical LS Port injection, I’d start with a blank set of flattops and cut them myself. Two different spray patterns that need two different piston dome designs.

 

Same thing I was wondering as well, what type of Fuel Injection is going to be ran.

 

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)

 

I thought the exhaust port on the LT flowed worse than the LS3 head. Is there really much of an advantage to doing this swap vs an aftermarket LS3 or LS7 head?

 

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 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.