Reducing compression, do it with heads or pistons?
Reducing compression, do it with heads or pistons? I have a SDPC LS2 402 with Diamond -13 or -14cc (need to do some digging on that one) dished pistons, and ETP 245 heads with 59cc chambers. I'd like to drop the compression on this motor for a turbo build. I think both pieces would survive a turbo build individually if left in place. Which would be better to swap/rework to lower the compression? I figure to get where I want to be, I need to get another 14cc out of each cylinder. I prefer to keep the ET heads, so perhaps having them re-worked to 72ish cc's? Or, I see Diamond makes -28cc pistons.
I'd love to hear peoples preferences on this.
I'd love to hear peoples preferences on this.
I'd start with talking to ETP about the heads, ask if they'd be comfortable modifying the heads to that extent or if they'd recommend swapping heads instead. Depending on the miles on the heads they might benefit from being worked again anyways.
If they recommend swapping, I'd weigh the price difference between losing money on yours and buying more vs new pistons with a rebalance. Depending on the mileage maybe you'd prefer a shortblock refresh anyways.
I don't know if you'd prefer to stay local or send it back to us, but whatever you decide we'd be more than happy to help you out with getting it where you want it to be if you go that route and would like us to.
How much power do you want to make? Boost level goals? You're talking about dropping the compression quite a bit. With Diamond pistons, I assume we also used Callies crank/rods at minimum, correct?
If they recommend swapping, I'd weigh the price difference between losing money on yours and buying more vs new pistons with a rebalance. Depending on the mileage maybe you'd prefer a shortblock refresh anyways.
I don't know if you'd prefer to stay local or send it back to us, but whatever you decide we'd be more than happy to help you out with getting it where you want it to be if you go that route and would like us to.
How much power do you want to make? Boost level goals? You're talking about dropping the compression quite a bit. With Diamond pistons, I assume we also used Callies crank/rods at minimum, correct?
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I don't have my calculator here, but I think he'd be going from about 11.1:1 down to 9.7ish
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800-456-0211 / PM / Facebook
WHIPPLE Superchargers, Procharger, Magnuson, Powerbond Sale, HPTuners packages!, Trickflow, AFR, PRC, CHE Trunion upgrade, $100 7.400" pushrod set, Custom Cam of your choice
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most engine builders agree that compression is best changed through piston dome/dish. When you upen up the combustion chamber in the head, you lose some of the important "quench". Obviously heads are much easier to change though.
Im no expert, but this is what I've been told by multiple engine builders
Im no expert, but this is what I've been told by multiple engine builders
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Verdad Gallardo I'd start with talking to ETP about the heads, ask if they'd be comfortable modifying the heads to that extent or if they'd recommend swapping heads instead. Depending on the miles on the heads they might benefit from being worked again anyways.
If they recommend swapping, I'd weigh the price difference between losing money on yours and buying more vs new pistons with a rebalance. Depending on the mileage maybe you'd prefer a shortblock refresh anyways.
I don't know if you'd prefer to stay local or send it back to us, but whatever you decide we'd be more than happy to help you out with getting it where you want it to be if you go that route and would like us to.
How much power do you want to make? Boost level goals? You're talking about dropping the compression quite a bit. With Diamond pistons, I assume we also used Callies crank/rods at minimum, correct?
If they recommend swapping, I'd weigh the price difference between losing money on yours and buying more vs new pistons with a rebalance. Depending on the mileage maybe you'd prefer a shortblock refresh anyways.
I don't know if you'd prefer to stay local or send it back to us, but whatever you decide we'd be more than happy to help you out with getting it where you want it to be if you go that route and would like us to.
How much power do you want to make? Boost level goals? You're talking about dropping the compression quite a bit. With Diamond pistons, I assume we also used Callies crank/rods at minimum, correct?
I've had the engine since '04 or early '05. Even though it spent a lot of time sitting for various problems, I think it's got enough runs/miles where I would prefer to tear it down anyway to check/replace the bearings before putting a turbo to it.
Here's the original thread from SDPC that I ordered/specced parts from:
https://ls1tech.com/forums/generatio...lock-sdpc.html
Says that it's an Eagle 4" forged crank, SCAT H-beam rods, and Diamond forged pistons.
I'm shooting for 750-800 tops (at least until I buy a different FMU someday) through the 4L80 with the GT91. Boost will have to stay capped at 15 psi. I'm looking at getting the compression down to about 10.0:1 so it still has plenty of off boost torque.
I just want to make sure im on the same boat as he is and trying to see if I should go the turbo route.My engine specs are almost identical as his but on a 408.I want to slap some 317 to get the compression down and a s91 turbo.
I always love doing my own building, but this might be one of those projects that I have to concede is just too time consuming to fab myself since I don't own a welder. I'll be getting parts as the money is available, starting with the turbo. Then I'll go with a T6 manifold kit based on reviews/availabilty. I don't expect it to be completed til next fall, but every journey has to start somewhere, right?
