josh2002-ws6

iTrader: (98)

Does anyone know the weight difference between the LQ9 block bored to 4.030 and the LS3 block? Thank you.

I am looking at different options for my next nitrous motor. I am not worried about money on this build. I would like to try and save some weight tho. I know the heads I already have will fit either a LQ9 with a 4.030 bore or a LS3 with the 4.070 bore. The extra 10ci with the LS3 would be nice, but mainly looking for the weight savings. Either motor will be getting a Lunati 4" crank, Lunati Pro Mod rods, and Diamond custom nitrous pistons. My current heads are AFR Mamofied 230's. They have 64cc combustion chambers. The motor is going in a all out race car. I will be spray a lot of nitrous, around 500 to 700 between 2 different stages of direct port. I want to put the biggest possible cam in the motor. Which block do you think will better suit my needs and wants?

Tainted

iTrader: (9)

Between iron and aluminum blocks the difference is usually about 110lbs

josh2002-ws6

iTrader: (98)

Ok, that's about what I was guessing. Do you think the weight saving is worth going with the LS3 block over the iron block LQ9 with that much nitrous? I know the iron block is tried and trued when it comes to big nitrous, but I am trying to save as much weight as possible.

Tainted

iTrader: (9)

Theres plenty of folks with big hp using the aluminum block. Personally id go aluminum and use arp bolts and call it a day.

87silverbullet

iTrader: (11)

You are asking alot from a stock block 4 bolt setup. Nitrous is violent in the chamber with the spike of cylinder pressure and you are planning on hitting it with between 500-700 in 2 stages which will still be violent.

Turbo cars make sick hp on 4 bolts but its not as violent. That is why they can get away with that a little easier than nitrous guys.

If you plan on going with that much and money is not a concern, send an LS3 block to ERL and let them sleeve it and do the 6 bolt conversion. That way you can use a 6 bolt head to add clamping force. AES can do the 6 bolt on your heads. ERL might be able to do it too but I haven't known them to do it.

I know AFR is a good head but going 400+cubes and spraying that much nitrous will make them a bottle neck. You are going to need something that breathes. Either get a bigger set of AFR's but then you still have a 4 bolt head, or go with a set of All Pro's. They have a .750 deck and 6 bolt. You can get all kinds of different port sizes and options. You can even step up to their LSW 12 which is an aftermarket LS7 head from them that can fit on a 4.000 bore if you get the smaller valves in them and they flow 400+cfm.

Another big question is which intake are you using? If its a factory style intake that will be another bottle neck for you. A carb style is better suited for high hp big nitrous. You have a lot more to be concerend about than just the block here. Do it right the first time or you will pay for it twice.

My6speedZ

iTrader: (18)

On top of that a big shot is easier to do on a single plane you can do a perimeter plate or a spray bar. To a point on a FAST you really need a DP even though there have been people out there that spray a **** load through a FAST plate.

Also I thought it was on about 80 pounds difference between truck block, LSX is more like 100.

josh2002-ws6

iTrader: (98)

I am spraying thru 2 stages of direct port. I also use a Vic Jr. with a single plane throttle body already. The Vic Jr is port matched to the AFR heads.

My6speedZ

iTrader: (18)

I re-read you original post, 500 to 700 shot is big block territory. You will defiantly need 6-bolt heads for something like that.

josh2002-ws6

iTrader: (98)

Tony Mamo said the heads should flow 355ish intake and 255ish exhaust after his port work. The only reason I am asking about using these heads on either one of these blocks is because I already have the heads and know they will sorta work on the blocks in question. If I am going to get bigger heads I am just going to go with a RHS or LSX block and go really big cubes.

My6speedZ

iTrader: (18)

No need to compromise cylinder wall thickness in pursuit of cubic inches if your going to be spraying on top of it. That is how I would approach it at least.

josh2002-ws6

iTrader: (98)

Ok, so what do you mean by that?

87silverbullet

iTrader: (11)

Well, that's what you need to do then. Sell everything and start a new game plan to hold that power level reliably.

Just some FYI, If you go with an ERL block you get a block that's just as strong and an RHS or LSX but it doesn't cost as much as an RHS and is a little bit more than an LSX but without the weight.

josh2002-ws6

iTrader: (98)

I guess that is what will end up happening.

I have the current setup and am trying to break the current stock cubic inch nitrous record into the 8's.

I was going to go with a tall deck RHS or LSX block if I build a new motor.

87silverbullet

iTrader: (11)

That is a tall feat right now with an f-body, plus you're running a 4l80e, that's alot of added weight. A guy with an rx7 has done it with a stock bottom end ls2. Camscam just hurt his motor yesterday and ran a 5.80 in the 1/8 which almost put him on an 8 in the 1/4.

When you say stock cubic inch, do you mean stock cubes with forged internals or stock cubes with stock internals?

Unless you have cut your cowl and your car is pure race car a tall deck wouldn't be a good choice. One of the mods here has cracked his RHS block and I think there were a few others.

josh2002-ws6

iTrader: (98)

My current motor has forged rods and pistons. I am only spraying 450 to 500 between the 2 stages. I know I have a heavier transmission, but it locks up to make up the difference. I have also done other stuff to pull the extra weight off. The car will have a 3k race weight.

My6speedZ

iTrader: (18)

Just that your saying if you change blocks your going to go big cubes and try and push alot of spray, big cubes sound cool but really large shots of nitrious creates massive cylinder pressure and your going to want to have strong cylinder walls. I wouldn't build anything larger than a 4.125 bore for a large nitrous LSX motor myself.

The biggest thing to worry about with a build like this is making sure your cylinder heads flows on the exhaust side not just the intake side. Getting a cam that has enough exhaust duration to help things.

What are your ET goals? be better to establish that first.

josh2002-ws6

iTrader: (98)

I was originally looking at building a RHS tall deck block to a 491ci motor. That would be using 4.125 pistons, 4.6 stroke crank, and 6.3 rods. I was looking at a huge custom set of Mast heads and using a custom dual single plane 4500 throttle body intake setup. I agree with not going over 4.125 bore. Ideally I would like to see very low 7's to high 6's in the quarter in a 3k weight Fbody.

bww3588

iTrader: (49)

Forget about the cubes, you will never notice 8 cubic inches between the 2 bores.

Worry about strength. You can't have your cake and eat it too unless you spend some big bucks. A stock ls3 block on that much sauce will be a ticking time bomb. Unless your going to spend the big bucks for an ERL or RHS aluminum block, find other ways to reduce weight.

Imo, even a stock iron block will be hard pressed under that much juice.

josh2002-ws6

iTrader: (98)

If I go with the RHS block and built it to the 491ci like I mentioned in the earlier reply. What do you think of that build with the said amount of nitrous and trying to reach my ET goals? Also, what would you recommend as the highest acceptable compression ratio? The car is race only and I will be using race gas only. What compression and what fuel? Thank you.

87silverbullet

iTrader: (11)

I was never a fan of being that over square on an engine but to each their own on opinions. 4.600 stroke vs 4.125 bore. I would talk to a reputable engine builder about that one like Erik at HKE or Kurt Urban at KUP.

If its a race application I would just go with somewhere in the 13-13.5 neighborhood and run c16 fuel. You can pretty much copy what ATV and Shiz in the nitrous section did. They run a 460 cube motor with 450 on it to run 7.80's. It has an F1 on it now though.