bdaniels3

Has any1 done a combo like this before or have any recommendations on what length of rod to use? Looking for whatever info that would be helpful.. I'm doing a 4.25 bore [no nitrous or boost] and probably 4.5 stroke, maybe a 4.425. Using GM performance LSX tall deck block. Thanks!

KCS

iTrader: (20)

I don't think there's room for 4.250" bore, so I think you mean 4.205".

Your rod length has to jive with the stroke and piston compression height. Callies has LSX rods in different lengths so you can theoretically fit a 4.5" stroke with a 6.340" Callies Compstar rod, and have a decent 1.13" compression height piston.

The problem you're probably going to run into is with the rod to camshaft clearance. The Callies rods have a good profile to clear the cam with larger strokes, but with a 4.50" crank, you are going to need a reduced base circle cam to get it to fit.

If you could afford to switch to an RHS tall deck block, you could go even bigger and have more clearance to run a bigger cam since the cam location is raised. I know of a 523ci RHS block in the works.

bdaniels3

The newer\newest lsx tall deck has max 4.25 bore. Only the tall decks bore can be maxed out to that. The 4.5 stroke does have to be used with a reduced 'small base circle' cam shaft. Which is fine with me. I just haven't came across any1 who has done this combo in lsx bowtie tall deck block. I have read and spoke with GM about the max bore and it definetly is 4.25 on their tall deck. The shorter deck can only go up to 4.25 stroke and I think but not sure bout the bore but believe it's around 4.125 area. I appreciate the info! If u happen to come across any1 who has a similar combo, I'd like to hear what rod length their using. I believe the smallest I can go is 6.3, just wondering what would work the best. I've thought about the RHS block but just can't come to spend 5k on it! Thanks again for the info

KCS

iTrader: (20)

Who said a 4.250" bore was ok at GM? The tall deck blocks still have a 4.40" bore spacing just like the standard deck blocks, so you're looking at only .150" between the bores. That's not a lot of area there for the gasket.

bdaniels3

With a 4.25 bore there is a .200 still. I honestly only plan on going to a 4.22 which isn't much difference but will still be enough room. They designed the block to even when it's spec'd out to 4.25 max bore that there is still .200 between cylinders. The camshaft area as well, is reinforced with more 'meat'

KCS

iTrader: (20)

Think about it. 4.40" bore spacing - 4.250" bore = .150". There is no way to have .200" between the cylinders with a 4.250" bore and a 4.40" bore spacing like they say.

You said you spoke with GM about this. Who did you speak with?

bdaniels3

Someone from GM performance parts. Yes, bore space is 4.4 and bore spacing is measured from the center of one cylinder to the center of the next cylinder. On a GM website it even says that the max bore is 4.25 and stroke 4.5 on their tall deck block. I think maybe bcuz they have a more beefier enforced deck with more metal in between. I even tried to double check on the enternet and found it said the same thing in multiple different auto forums and racing websites etc'

bdaniels3

KCS

iTrader: (20)

http://media.gm.com/media/us/en/chev...lsx-block.html

bdaniels3

bdaniels3

bdaniels3

Regardless of what size is the max, I myself only plan on going either 4.2 or 4.22. I spoke with someone who said they built an lsx block for a guy with 4.25 bore and he made the custom pistons and crankshaft for the build. He said it's ran nice for around 1.5yr now. He actually builds race lsx style engines for 20+yrs. U can find alot of his custom engines on ebay and elsewhere. His name is Jerry. Most of the custom lsx engines on ebay are his. He is with SAG performace. Anyway I'm not here to argue with a fellow LS guy by any means. So if you have any additional helpful info, I appreciate it. Like I said in the first couple post, I only plan on going around 4.2 bore anyway so there's no since in arguing about it. Thanks for ur info anyway though!

KCS

iTrader: (20)

Just trying to get you to use your brain. I've built LSX engines for years and the max bore has always been 4.205". There is no way to get .200" between the cylinders with a 4.40" bore spacing and a 4.250" bore, but you can with a 4.20" bore.

It's simple math. Just like how you it's impossible for someone to have built LS engine for "20+ yrs" when the LS engine isn't even 20 years old yet.

bdaniels3

He has been building race and lsx for over 20yrs. Obviously the lsx is pretty near the 20 year mark. Enough for comparison. I don't need to talk up his expertise. His credits are enough. Obviously it can be bored out to 4.25 seeing as many people have already done that with no problem. I'm not here to argue with someone, I come here to learn. Being as you can't ever know enough. Not that 5 hundredths of an inch is going to matter m7ch in my case anyway

bdaniels3

I mean chevy\GM performace says it right on their website where u can order the block from. Possible for over 500ci. As well they also sell a gasket for a 4.250 bore. 4.200 bore and 4.5 stroke isn't Gona get u to even 500ci in just the block dimensions itself. I don't understand why they would sell a 4.250 gasket if the max bore is 4.200

KCS

iTrader: (20)

The 6.0L headgasket has about a 4.050" bore. The 6.2L gasket has about 4.100". The headgasket bore is usually bigger than the cylinder.

panic

I wonder what the upper bore limit is before the cylinder walls are no longer round when up to full load & temperature?
GM didn't know about this in the small block until the 1970s - Jenkins discovered that over than .030" lost ring seal.

Obviously, the GM ".200 remains with 4.25 bore" advisory was from the sales department, which by definition is staffed by people to whom math is an unknown and frightening concept.

bdaniels3

Lol. I wondered when he was telling me that bcuz it didn't make sense in my mind but then it says that on like 3 different websites. When they came up with the idea for an 'aftermarket' lsx block, that was what brought the whole idea to life was having an engine u could bore the **** out of. I wish someone with a 4.25 bore would chime in and tell about what setups he is running. I'm not really looking to do it myself but it'd be cool to hear about. IS THERE ANY1 RUNNING ANYTHING BIGGER THAN 454CI OUT THERE. Would love to hear about ur setup

Blown06

iTrader: (32)

Dude, this is like arguing with an engineer that designed something but has never built anything. The physics and math work like this:

If you have a bore space of 4.400" and a bore diameter of 4.25": 4.400-4.25=.150".

God himself could not bore a 4.400 bore space block to 4.250" and have .200" between the cylinders.

I don't give a **** what Summit or anyone else wrote on their website. It is simple ******* math.

Now, if you show me an lsx block that is bored 4.250" and it has .200" of deck surface between the bores, you no longer have a 4.400" bore space block. In some instances, and if the cylinder wall thickness allows, I have seen guys slightly stretch bore space on a cnc machine. But that is not the point, because you don't have a 4.400" bore space anymore.

Why is this such a hard concept for bdaniels to grasp????? I guess because the internet NEVER lies. lol

bdaniels3

Obviously blowing **** didn't read the whole thread. Yes we know there is only .2 left. We are discussing max bore. Next time read the entire thread dumbass !