Engine build question for road racing
Thread Starter
Instructor
Joined: Nov 2015
Posts: 245
Likes: 4
From: Oklahoma City Oklahoma
Engine build question for road racing
I'm torn between building an LS7 or LSX for road racing. Here are my thoughts:
My last LS7 was overbored to 432 (from previous owner) with forged pistons. The cylinder wall cracked in under 200 miles. My immediate thought was I'll build an LSX to be sure to have that reliability, but of course the con is that it's 100lbs heavier, isn't ideal. My question is, is it possible to have a forged piston LS7 and still keep reliability even on the track with 15 minute sessions? Or is that asking too much of the block?
My options right now are to reuse my current pistons and other internals and slap it all in the LSX. Option B is to use another LS7 and just get new pistons for it so it's not super overbored. What do you guys think? Anyone here road race with forged slugs in their LS7?
My last LS7 was overbored to 432 (from previous owner) with forged pistons. The cylinder wall cracked in under 200 miles. My immediate thought was I'll build an LSX to be sure to have that reliability, but of course the con is that it's 100lbs heavier, isn't ideal. My question is, is it possible to have a forged piston LS7 and still keep reliability even on the track with 15 minute sessions? Or is that asking too much of the block?
My options right now are to reuse my current pistons and other internals and slap it all in the LSX. Option B is to use another LS7 and just get new pistons for it so it's not super overbored. What do you guys think? Anyone here road race with forged slugs in their LS7?
Thread Starter
Instructor
Joined: Nov 2015
Posts: 245
Likes: 4
From: Oklahoma City Oklahoma
Edit: sorry just saw you said stock. stock is only 450whp ish and has all of the cylinder walls in tact. I'll be building either an LS7 or LSX. Just trying to figure out best route. I'm at 560whp and if forged pistons go in the cylinder wall will be a bit thinner, which is my concern.
Last edited by Eyedeas; Feb 26, 2016 at 09:23 AM.
Race Director
Joined: Aug 2005
Posts: 13,592
Likes: 187
From: Hudson WI
NCM Sinkhole Donor
Stock piston or forged?
Edit: sorry just saw you said stock. stock is only 450whp ish and has all of the cylinder walls in tact. I'll be building either an LS7 or LSX. Just trying to figure out best route. I'm at 560whp and if forged pistons go in the cylinder wall will be a bit thinner, which is my concern.
Edit: sorry just saw you said stock. stock is only 450whp ish and has all of the cylinder walls in tact. I'll be building either an LS7 or LSX. Just trying to figure out best route. I'm at 560whp and if forged pistons go in the cylinder wall will be a bit thinner, which is my concern.
Last edited by timd38; Feb 26, 2016 at 10:07 AM.
Le Mans Master
Joined: Oct 2012
Posts: 8,434
Likes: 411
From: Texas
The LS3 is the reliable engine and really you can buy a used one and get this thing going for a lot less money.
Stock short block with a cam, some head porting, recycle your bolt ons and you can have a very reliable 515 rwhp or so for a LOT less $. And if it blows you aren't out too much $ anyways.
Stock short block with a cam, some head porting, recycle your bolt ons and you can have a very reliable 515 rwhp or so for a LOT less $. And if it blows you aren't out too much $ anyways.
Race Director
Joined: Aug 2005
Posts: 13,592
Likes: 187
From: Hudson WI
NCM Sinkhole Donor
The LS3 is the reliable engine and really you can buy a used one and get this thing going for a lot less money.
Stock short block with a cam, some head porting, recycle your bolt ons and you can have a very reliable 515 rwhp or so for a LOT less $. And if it blows you aren't out too much $ anyways.
Stock short block with a cam, some head porting, recycle your bolt ons and you can have a very reliable 515 rwhp or so for a LOT less $. And if it blows you aren't out too much $ anyways.
Thread Starter
Instructor
Joined: Nov 2015
Posts: 245
Likes: 4
From: Oklahoma City Oklahoma
I don't really want an LS3 to be honest. I'm just trying to figure out if forged pistons with an LS7 is doable while still maintaining reliability of the block itself. I don't want to have another cracked sleeve 
Thread Starter
Instructor
Joined: Nov 2015
Posts: 245
Likes: 4
From: Oklahoma City Oklahoma
Sleeves LS7 would be ideal, but it's not in the budget unfortunately. Just trying to see if anyone had some longevity with racing 4.130" bore LS7 with forged slugs.
Last edited by Eyedeas; Feb 26, 2016 at 06:24 PM.
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Thread Starter
Instructor
Joined: Nov 2015
Posts: 245
Likes: 4
From: Oklahoma City Oklahoma
So my logic is forged and very close to stock bore, versus the bored to **** that it was.
Basically, I'm wondering if others have done this and used forged 4.125 or 4.130 bore and used it reliably, instead of 4.15 that it was likely close to before.
Thread Starter
Instructor
Joined: Nov 2015
Posts: 245
Likes: 4
From: Oklahoma City Oklahoma
600whp is plenty. I'm about 40 short of that so that's my margin for error. But if the LS7 can handle that with forged Pistons and a very light bore or hone, then that's the route I want to go. But looking for people who have done that who can share their experience.