LSX tall deck block dimensions

[98TransAmWs-6]

Hey guys I need some clarification on a couple of things. I am looking at building a 500+ CID NA engine with the tall deck LSX block and as of right now I am just trying to add up the total price of what I will be spending so I can build a budget for it. On the block on various sites such as summit racing and GMHP Magazine it says the max bore is 4.25" and the max stroke is 4.5" and again those are the max dimensions for the TALL DECK version. So I emailed Texas Speed and they told me that the max bore is 4.20 and 4.250 stroke but their site says otherwise. On their site it says a max bore 4.250 and a max bore of 4.375 and that it is possible to build 500+ cid engines with the LSX tall deck block. They basically called me an idiot and would not answer anymore emails. My question is what are the real maximums for the tall deck version, is it what I read, 4.250 bore and 4.5 stroke?

[35th-ANV-SS]

511 is the limit I believe. 4.25" bore and 4.5" stroke. Let a 2nd person confirm that.

[98TransAmWs-6]

511 is the limit I believe. 4.25" bore and 4.5" stroke. Let a 2nd person confirm that.

That is what I thought.


My message to TSP:

Me: Hi,
I am planning on building a NA monster for my 98 Trans Am and am going to use the GMPP LSX bowtie tall deck block. My plan is to have the bores enlarged to 4.250" and a 4.5" stroke but I was wondering if you guys could lay out all the exact rotating assembly components and the cost for them so I can plan out my budget for this build.

Thanks,
Will

John@TSP: Will,

I am sorry but we can not help with this. The Max bore on a LSX block is 4.200 and that much stroke is asking for a disaster. The largest we typically go is a 468 which is a 4.185 bore with a 4.250 stroke.

Thanks John J

Me: Okay then I was given the wrong information. I saw on different sites that the max bore was 4.250 for bore and 4.5 stroke, places such as summit and gmhp magazine have this listed as such. Your site also says it can be stroked out to 500+ cid so I am a little confused. I really want a 500+ ci, so if that isn't possible on the lsx is there a block that this can be done on?

John@TSP: Will,

There are multiple issues with what you have asked for. Like stated earlier the max bore is a 4.200” The bore spacing on these blocks is a 4.400 so if you somehow were able to pull off a 4.250 bore you would have absolutely no room for any kind of head gasket. A 4.500 stroke is way too long to work in this motor. It would cause the rods to hit the cam, obviously a motor can not work when the rods hit the cam. You may be able to find a shop that says they can build this for you, but we will not. The motor would be a ticking time bomb.

Thanks John J

Me: I understand what you are saying and that it is a ticking time bomb and I am not trying to get you guys to build a motor that will be a disaster and I respect that, that is a great quality for a builder one that doesn't just build whatever. Would it be possible to do this then: 4.20 bore and 4.375 stroke?

This might help you understand what I am trying to do. I want to build the biggest NA engine possible that is reliable and I want to be pushing 650-800+ hp if possible without FI.

They never responded to my last email so I am going to go with a different company such as vengeance. This isn't the first time I have received this sort of treatment from them.