LS838 build
05-03-2021, 04:59 PM
#1
LS838 build
Hey guys,
So Covid totally screwed my ideas to build my 434 stroker that I was really looking forward to. My consolation? I found a good ls1 block and some -7cc diamond pistons with it for $300. I kept my rotating assembly once I found this block. Is it worth keeping the -7cc pistons if running N/A or should I look at some flattops? I could just get some heads milled to like, 61 or 62cc to keep the compression up right? Just looking for ideas.
The build is looking something like this.
LS1 block
-7cc diamond pistons (Came with block)
eagle 4" crank, 6.125" Mahle Rods
Heads are TBD, but I"m looking at either some ported 243's or maybe the TSP As Cast trickflow's with matching cam. Someone mentioned Tony Mamo's small bore heads but that's a lot of cash. My goal..while I would love to see 500 wheel hp, I would prefer a torque monster street car with power from 2000-6500.
So Covid totally screwed my ideas to build my 434 stroker that I was really looking forward to. My consolation? I found a good ls1 block and some -7cc diamond pistons with it for $300. I kept my rotating assembly once I found this block. Is it worth keeping the -7cc pistons if running N/A or should I look at some flattops? I could just get some heads milled to like, 61 or 62cc to keep the compression up right? Just looking for ideas.
The build is looking something like this.
LS1 block
-7cc diamond pistons (Came with block)
eagle 4" crank, 6.125" Mahle Rods
Heads are TBD, but I"m looking at either some ported 243's or maybe the TSP As Cast trickflow's with matching cam. Someone mentioned Tony Mamo's small bore heads but that's a lot of cash. My goal..while I would love to see 500 wheel hp, I would prefer a torque monster street car with power from 2000-6500.
05-03-2021, 05:30 PM
#2
Re: LS838 build
I'm not intending to sound like a jerk but it might sound that way.
You're only asking if you should keep pistons but you really don't have enough pertinent information to define if those pistons are worth your time. No piston information other than cc. No confirmation on head. No confirmed crank. No targeted compression ratio. No defined goals.
So yeah, they're maybe or maybe not good for your build. If you're just brainstorming a build then pistons are low on the worry list as of yet.
You're only asking if you should keep pistons but you really don't have enough pertinent information to define if those pistons are worth your time. No piston information other than cc. No confirmation on head. No confirmed crank. No targeted compression ratio. No defined goals.
So yeah, they're maybe or maybe not good for your build. If you're just brainstorming a build then pistons are low on the worry list as of yet.
Last edited by aliceempire; 05-03-2021 at 05:35 PM.
05-03-2021, 10:19 PM
#3
Re: LS838 build
I'm not intending to sound like a jerk but it might sound that way.
You're only asking if you should keep pistons but you really don't have enough pertinent information to define if those pistons are worth your time. No piston information other than cc. No confirmation on head. No confirmed crank. No targeted compression ratio. No defined goals.
So yeah, they're maybe or maybe not good for your build. If you're just brainstorming a build then pistons are low on the worry list as of yet.
You're only asking if you should keep pistons but you really don't have enough pertinent information to define if those pistons are worth your time. No piston information other than cc. No confirmation on head. No confirmed crank. No targeted compression ratio. No defined goals.
So yeah, they're maybe or maybe not good for your build. If you're just brainstorming a build then pistons are low on the worry list as of yet.
The block is an ls1 block. The crank is an eagle 4" stroke crank. The rods are Mahle H-beam forged 6.125". The intake is a FAST 102. This, along with the pistons are what I have in my garage right now. I need more $$$ before I throw down on heads and cam.
The Pistons are 11504 diamond pistons. They came with the block so an they are used but appear to be in decent shape so I was thinking of using them. I'm not set on heads yet but I'm building an NA motor, not boost. My question was, do I get heads milled to accept the -7cc of the pistons or sell the pistons and get heads that aren't milled. If I sell the pistons I'll set me back because it's something I wasn't necessarily planning on spending money on at this juncture. If it makes sense to keep the pistons, then I'll just do that. If it doesn't, then I'll look into getting a set of flat-tops.
Link to the pistons here: Diamond 11504 Pistons
Targeted compression ratio would be for 91 octane around 11:1. I've read I can go as high as 12:1 but that seems to be asking a bit much. The heads I buy will be dependent on if I keep these pistons. Maybe more precisely the CC of the heads...I think I have to be 61 or 62 cc chambers to get 11:1 on these pistons.
I'm not real smart when it comes to putting stuff like this together so I was just looking for some advice is all.
Last edited by Ozz1967; 05-03-2021 at 10:22 PM.
05-03-2021, 11:08 PM
#4
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Re: LS838 build
I assume the -7cc is just a large fly cut for valves? You're probably going to need some amount of valve relief for the lift you run, so you'd just end up cutting into flat tops anyway.
05-04-2021, 07:15 AM
#5
Re: LS838 build
I'm assuming some numbers (deck height and head gasket) to get compression ratio but 61cc chambers and those pistons gave me a rough 10.8. I wouldn't fuss over less than a quarter point of compression. With everything measured out and compression correctly calculated, you'll be in the high 10s which is plenty fine for street lsx. I've never dealt with diamond pistons myself but they aren't cheapy rebuilder pistons so compression height and overall quality is probably just fine. As Qwk already said, large enough cam and you'll need the piston to valve clearance anyway.
Last edited by aliceempire; 05-04-2021 at 07:40 AM.
05-04-2021, 08:47 AM
#6
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Re: LS838 build
If you are staying N/A the power will be in the heads. Tony sells all kinda of combo's and can work with your budget. His as cast sportsman heads are incredible and more in line with the other aftermarket heads. I would start reading up on 383 builds, as well as playing with compression ratio and displacement calculators. Those pistons may or may not end up working depending on where the final bore lands on your block. You may be better off just selling them now and start with more bore.
05-04-2021, 01:31 PM
#7
Re: LS838 build
If you are staying N/A the power will be in the heads. Tony sells all kinda of combo's and can work with your budget. His as cast sportsman heads are incredible and more in line with the other aftermarket heads. I would start reading up on 383 builds, as well as playing with compression ratio and displacement calculators. Those pistons may or may not end up working depending on where the final bore lands on your block. You may be better off just selling them now and start with more bore.
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05-04-2021, 03:16 PM
#9
Re: LS838 build
I'm assuming some numbers (deck height and head gasket) to get compression ratio but 61cc chambers and those pistons gave me a rough 10.8. I wouldn't fuss over less than a quarter point of compression. With everything measured out and compression correctly calculated, you'll be in the high 10s which is plenty fine for street lsx. I've never dealt with diamond pistons myself but they aren't cheapy rebuilder pistons so compression height and overall quality is probably just fine. As Qwk already said, large enough cam and you'll need the piston to valve clearance anyway.
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