What bore is too big for boosted LS3?
08-04-2014, 06:38 PM
#1
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What bore is too big for boosted LS3? I picked up a forged LS3 with a set of Mahle 4.065 pistons in it. The cylinder walls have some marks on them that can be felt with a fingernail. Honestly it looks like someone fell asleep while running a flex hone in the cylinder. I plan on running ~20 lbs through an S480 on it.
My question is how thin is too thin on the cylinder walls of an LS3 when using boost? If I have have to have the cylinders opened up to a 4.070 or even 4.075 is that going to cause me problems?
My question is how thin is too thin on the cylinder walls of an LS3 when using boost? If I have have to have the cylinders opened up to a 4.070 or even 4.075 is that going to cause me problems?
08-05-2014, 06:23 PM
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More details. Wiseco makes a 4.070 piston I could run to get me where I want to be compression wise. I'm trying to figure whether or not to spend money on this motor or sell it for what I have in it and move on to a different idea.
08-05-2014, 07:48 PM
#5
^^ Agreed, This was sent to a friend of mine from Jegs, it was sent to Jegs from a GM engineer, after he could not get an LSA block without horrible core shift. Jegs sent him 3 blocks that were unacceptable.
""The following information applies to all LS3 LSA LS9 production and performance engine blocks and addresses the liner being off center.
0.048” is the minimum liner thickness when measured at the flange, (i.e. Deck surface) this is a production tolerance spec.
0.043” is the is the minimum liner thickness when measured at the liner body, (i.e. anywhere 1 inch lower than the deck surface) this is also a production tolerance spec.
Dealers should be urged to get actual sonic test data before warranting these blocks for this. Brand Quality will be starting auto return projects on these blocks so if warranted they will be called back for inspection, If at inspection they find the wall thickness to be with specs the dealer will be debited for the claim and have the opportunity to have the block shipped back to them at their cost.
These production specs are good for the production HP levels of the our engines, 420 - 640 hp.
If a builder is purchasing these blocks for an engine with an anticipated HP level above 640 hp or they are boosting the engine or are intending on opening the bore up over 4.065; PCC should strongly push the builder to consider an LSx block which can easily handle well over 640 hp, boosting or an over bore."
""The following information applies to all LS3 LSA LS9 production and performance engine blocks and addresses the liner being off center.
0.048” is the minimum liner thickness when measured at the flange, (i.e. Deck surface) this is a production tolerance spec.
0.043” is the is the minimum liner thickness when measured at the liner body, (i.e. anywhere 1 inch lower than the deck surface) this is also a production tolerance spec.
Dealers should be urged to get actual sonic test data before warranting these blocks for this. Brand Quality will be starting auto return projects on these blocks so if warranted they will be called back for inspection, If at inspection they find the wall thickness to be with specs the dealer will be debited for the claim and have the opportunity to have the block shipped back to them at their cost.
These production specs are good for the production HP levels of the our engines, 420 - 640 hp.
If a builder is purchasing these blocks for an engine with an anticipated HP level above 640 hp or they are boosting the engine or are intending on opening the bore up over 4.065; PCC should strongly push the builder to consider an LSx block which can easily handle well over 640 hp, boosting or an over bore."
08-06-2014, 01:34 AM
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Based on personal experience for 20 lbs. is definitely iron block, an lQ9 can handle 1000 plus foot lbs. torq all day.
Best block for the coin is LSX with priority main oiling and 6 bolts per cylinder, will be rock solid foundation for power longevity and trouble free do all you want day in day out year around.
The LS engine block works best for boost at SMALLER cubic inches, I seen 402 Ci ls2 at around 1k horse power stretch like a robber band between head bolts, loosing head gasket seal between block and head gasket which means the block was stretching.
For starters if the head gasket leak is between the head and the gasket, that means THE HEAD was lifting.
Must don't understand (head lifting) and think using a stronger stud will eliminate the problem, fact is lifting is not from stretching of the stud or head bolt, but an arch forms on the head structure between studs, those why the correction to these reality comes in the form of 6 bolts per cylinder blocks and heads.
I installed O rings on LS2 head and block and guess what, still leaked on the block side of the gasket at which time I opted for an LQ9 block, the LS2 block had to stretch over .013 at deck surface to be able to leak pass the wire and it did. And yes using copper head gaskets.
Limits are there no question.
Hope this helps OP work less have more fun with the project and avoid costly lessons, "and" a front road seat in the classroom of the school of hard knocks.
Best block for the coin is LSX with priority main oiling and 6 bolts per cylinder, will be rock solid foundation for power longevity and trouble free do all you want day in day out year around.
The LS engine block works best for boost at SMALLER cubic inches, I seen 402 Ci ls2 at around 1k horse power stretch like a robber band between head bolts, loosing head gasket seal between block and head gasket which means the block was stretching.
For starters if the head gasket leak is between the head and the gasket, that means THE HEAD was lifting.
Must don't understand (head lifting) and think using a stronger stud will eliminate the problem, fact is lifting is not from stretching of the stud or head bolt, but an arch forms on the head structure between studs, those why the correction to these reality comes in the form of 6 bolts per cylinder blocks and heads.
I installed O rings on LS2 head and block and guess what, still leaked on the block side of the gasket at which time I opted for an LQ9 block, the LS2 block had to stretch over .013 at deck surface to be able to leak pass the wire and it did. And yes using copper head gaskets.
Limits are there no question.
Hope this helps OP work less have more fun with the project and avoid costly lessons, "and" a front road seat in the classroom of the school of hard knocks.