Generation IV External Engine - Alluminum vs Iron

So I have an opportunity to pick up an LQ4 with 317 cheap ($450.00) and I dont know if its worth the extra weight to have the iron block or if I should just build up my LS1. The LQ4 is pulled from a stock truck, evidently a ring broke and needs a new piston ring but didn't scar anything up. My LS1 has the LS6 Intake Manifold and the 243 heads. The rest of the guts are all stock. So with a $2000 budget and possibly able to sell my old motor for about $1200 with stock intake and 853 heads. Is it worth the weight going iron? I "could" forsee a FI build going on but if that happened, it would be down the road a couple years. Anyhow, just basically wondering if its worth switching blocks. Either way, something is getting rebuilt soon.

Forgot to mention, I'm looking for about 650 RWHP on a daily driver

I would imagine there would be a significant amount of additional weight with the iron, plus you have the problem of rust over time. I don't understand why they don't imploy steel or some nickel alloy that is vastly superior to iron if you're gonna put up with that amount of weight.

I'm not sure what iron blocks have to offer that's better than the aluminum, but I've read that the LSX iron motor is supposed to have a threshold of 2500 BHP.

lq4 would be a good foundation for future big cubes, like a 408. you only pick up 70lbs of weight. ive got the lq4 in mine and im about to stick the l92 heads on it. later on i will do the 408 and it will go great with the l92 heads. rust? i dont know what the hell the other guy is talking about. these engines dont rust unless you pull it apart and leave it sitting in the yard.

lq4 would be a good foundation for future big cubes, like a 408. you only pick up 70lbs of weight. ive got the lq4 in mine and im about to stick the l92 heads on it. later on i will do the 408 and it will go great with the l92 heads. rust? i dont know what the hell the other guy is talking about. these engines dont rust unless you pull it apart and leave it sitting in the yard.

+1 on that never can go wrong with larger displacement, plus like mentioned the 6.0 allows for the use of L92 heads where as the smaller ls1 bore wont allow it....No rust issues..... there are plenty of 60s and 70s era cast iron 350s running around no problem....rust is no real issue, clean the block up and paint it.......70lbs isnt a big weight issue either...

you must be like me and want it to turn an a dime and be very precise, I am going 383 when the time comes becauce i love my handling charactertstics and plan o making it even better It can be done quite easily and for the most part cheaply. Just gonna stroke my LS1 or go 402 funds permitting when it's time.

70 pounds over the nose is more wieght for the rear tires to fight to get the car moving; so less traction from a dig. This is the only difference in performance if you just want to drag with that much power. I say keep the aluminum block and forge what you can.

Alluminum, is that one of those new high performance metals? :jest:

I would go with the iron 6.0 block. You can do a lot more with that wider bore. After hearing about oiling problems common to the 383s I am not sure I would want to go that route. What heads do you plan on running on it? 243 will make your compression high, the 317 are good for boost. And you can always run L92 heads...

I went LQ4 and didn't notice any difference at all in the way the car handles... the bigger cubes also allows for a steady TQ curve across the WHOLE rpm range as well... doesn't drop like smaller engines would...

I went LQ4 and didn't notice any difference at all in the way the car handles... the bigger cubes also allows for a steady TQ curve across the WHOLE rpm range as well... doesn't drop like smaller engines would...

I bet your LQ4 does have a very steady torque curve with the bigger cubes and the smaller 224 cam in there. That's got to be a very streetable choice that will still put out some nice power everywhere in the RPM range.

So, what did you get?

Alluminum, is that one of those new high performance metals? :jest:

I would go with the iron 6.0 block. You can do a lot more with that wider bore. After hearing about oiling problems common to the 383s I am not sure I would want to go that route. What heads do you plan on running on it? 243 will make your compression high, the 317 are good for boost. And you can always run L92 heads...

I agree.

actually lighter isn't always better when it comes to handling. in 04 they tested a bullit a mach one and cobra mustangs. the best handleing was the bullit with a iron block and heads followed by the mach one with a iron block and al heads then the cobra with al block and heads. the 600foot slalom speeds were almost 2mph different between the three car's.

So, what did you get?

I bought an LQ4, L92 heads, L76 intake, 4" forged eagle stroker crank, 6.125 forged eagle rods, 4.030 JE pistons.

Now I'm debating boost or nitrous. tough freaking decision. I've got pistons set up for boost but I dont know if I wanna go that route as this is getting very expensive, very fast. Already got over 3k invested and havnt had any machine work done.

So the iron block is capable of a bigger bore? 70 lbs, I thought it would be more. I've been trying to find out the difference between the two blocks, the LS2 is 6.0, are these sleeved or are they coated walls? Is the truck block the same bore, still trying to figure out why/what the difference is between the 402 & 408.

Well, The LS2 is a sleeved aluminum block, the LQ4 is an Iron Block. The Iron block is a tad bit bigger. Iron block will inherently hold more boost/nitrous because of its composition. The LQ4 is 364 cubic inches, and not sure of the LS2 but I know its a little less.

actually lighter isn't always better when it comes to handling. in 04 they tested a bullit a mach one and cobra mustangs. the best handleing was the bullit with a iron block and heads followed by the mach one with a iron block and al heads then the cobra with al block and heads. the 600foot slalom speeds were almost 2mph different between the three car's.

Were they all stock 04 cars? I only ask because lighter is pretty much always better unless theres a rediculous difference in weight distribution (some of which can be accounted for in the suspension setup). Plus the cobra would have had an iron block with a big metal blower on top, a heavier tranny, heavier interior, and heavier rear suspension.

there is about a 90lbs difference

it's actually closer to 110lbs :D

Well, The LS2 is a sleeved aluminum block, the LQ4 is an Iron Block. The Iron block is a tad bit bigger. Iron block will inherently hold more boost/nitrous because of its composition. The LQ4 is 364 cubic inches, and not sure of the LS2 but I know its a little less.

I could have sworn LS2's were 364 cubic inches too. IIRC theyre the same size. And I thought iron blocks were more closer to 100 lbs. heavier as well.

If u r building over 600 hp, I would suggest you go w the lq4. I would never say the aluminum block couldn't handle that power for long, as there would be a thousand guys on here saying thats what they are running. I have an lq4 that I am running in my truck w ls3 heads and I have no worries of the bottom end going and taking my block w it. they are about a seventy # weight dif, but bigger bore can make up for that w torque all over the chart.

If u r building over 600 hp, I would suggest you go w the lq4. I would never say the aluminum block couldn't handle that power for long, as there would be a thousand guys on here saying thats what they are running. I have an lq4 that I am running in my truck w ls3 heads and I have no worries of the bottom end going and taking my block w it. they are about a seventy # weight dif, but bigger bore can make up for that w torque all over the chart.
this is what i'm doin. i was originally goin with a 383 LS1 but when i talked with my engine builder he told me of the problems of aluminum blocks with the high numbers i should be putting and suggested we change the build from a 383 LS1 to a 402 iron LQ4 . . . it'll be forged so the bottom end wont worry me :D

Here is some info that can help in here..

LS1- 346ci 5.7l
LS2- 364ci 6.0l
LQ4/9-364ci 6.0l
402- 6.6l, it's a 6.0l with a 4" Stroke Crank, 4.000" Bore
408- 6.7l, it's a 6.0l with a 4" Stroke Crank, 4.030" Bore.

Weight difference between an Aluminum Block and Iron Block is about 84lbs..that is the number I have seen in quite a few places researching it.

As fas as durability..I bet I can beat the shit out of my Iron 408 and it will hold up longer than any Aluminum Block.

actually lighter isn't always better when it comes to handling. in 04 they tested a bullit a mach one and cobra mustangs. the best handleing was the bullit with a iron block and heads followed by the mach one with a iron block and al heads then the cobra with al block and heads. the 600foot slalom speeds were almost 2mph different between the three car's.

The part of the story you are missing is, an iron block 2v, and an aluminum blocked 4v weight nearly the same. The 4v weight is set wider in the engine bay as well.

To the OP if you haven't noticed by now you should realize that all the guys running Alum. blocks are telling you to run Alum. all the guys running Iron are obviously telling you to run Iron. Everyone chose what they're running *hopefully* because it suited their purpose.

Here is what you have to do, figure out what purpose you want the engine to serve.

Alright first off you want to hit 650 rwhp in a daily driver thats an issue in itself but reserved for a different time. Both blocks are "capable" of this no questions asked... however no questions about it an Iron block can do it safer and cheaper. Alum. Can aswell but it will require an LS2 or better block to do it safely.

If you're looking for reliable, daily driving, occasional drag racing performance on a budget no questions asked get the Iron block. If you're at all concerned with handling, and an overall better more comfortable ride quality and have the extra bucks to accomplish it. Go with the Alum.

You will get people on both sides saying how one is better then the other but again I stress its all in what you want to do and what money you want to spend doing it. I guarantee both engine types have seen the goals you're trying to hit without issues.

actually lighter isn't always better when it comes to handling. in 04 they tested a bullit a mach one and cobra mustangs. the best handleing was the bullit with a iron block and heads followed by the mach one with a iron block and al heads then the cobra with al block and heads. the 600foot slalom speeds were almost 2mph different between the three car's.

Mach one's have aluminum blocks. And a bullitt is nothing more than a rebadged GT and those have aluminum blocks as well, with the difference in the engine being a revised intake manifold. And all the mod motors that went into mustangs have aluminum heads. In fact in that body style (new edge 99-04) only the 03-04 Cobras had iron blocks. But still retained the aluminum heads.

so ican never remember wat the difference is between the lq4/9

Pistons..the LQ4 is 9.4: Comp, the LQ is 10.0:1 Comp.

Wow this thread got resurrected from the dead. I went with an LQ4 and a Procharger. I've tied up a hell of alot of money in this build and decided the car will never again be a daily driver. IMHO the iron block will handle a F1 Procharger a hell of alot more reliably than an aluminum block. So far I couldn't be happier with my decision. My ride height up front didnt seem to change, I have a HELL of alot more power than I had with my LS1, and besides a 9" with a full spool my ride quality hasn't really seemed to change.

The difference in a 402 and a 408 is in a 402 u keep the factory bore of 4.0 instead of boring it out. 030 and using oversized pistons. Everything else is the exact same

iron 364 LY6. Best bang for the buck motor around, period.

Ive been running the aluminum LS2 block bored .030 over (4.030") for four years now and with a 350 shot of nitrous off the line at the track, and a lot of hard runs shifting a 7400 rpms,And street running. The LS2 is a very strong block, Im proof of that, and its still going strong, Im now starting a new build with the new LS3 aluminum block with it bored to.030" (4.095) = 431cid.

Ive been running the aluminum LS2 block bored .030 over (4.030") for four years now and with a 350 shot of nitrous off the line at the track, and a lot of hard runs shifting a 7400 rpms,And street running. The LS2 is a very strong block, Im proof of that, and its still going strong, Im now starting a new build with the new LS3 aluminum block with it bored to.030" (4.095) = 431cid.

It took you a 350 shot to run 6.50's in the 1/8th... LOLs What are you running it in... a fuckin tank?

Alluminum, is that one of those new high performance metals? :jest:

I would go with the iron 6.0 block. You can do a lot more with that wider bore. After hearing about oiling problems common to the 383s I am not sure I would want to go that route. What heads do you plan on running on it? 243 will make your compression high, the 317 are good for boost. And you can always run L92 heads...
i'll be running stage 2 243's with 67cc's and possibly -15 dish-top piston and i'll be at 9.5 to 1 on my iron block

I agree the LS2 is a strong block. Take it a step further and add the ERL superdeck system with 6 bolt heads and it simply blows the iron blocks out of the water. For a forced induction application there really is no contest with the trusses they build into the block and the six bolt heads. Like an earlier post stated, its all about what your intended use will be. Why spend money where you dont need to. Unless you are crazy about shaving weight, I would stick with iron at your power level.

I have no doubt the LS2 is a great block for head, cam packages and occasional nitrous. But when it comes to boosting I think an iron block is more suitable

If you're arguing weight, it doesn't take a whole lot of effort to take 84 lbs out of a street car. If its purely race, it may cost you for some 7071 parts here and some carbon there, a dash of Titanium, but it can be taken out.

I voted for the LS1

if 60-80lbs of weight (and block strength, mind you) really bothers you ... then you probably have other things to worry about before weight... mind you, the LQ4 and LY6 run really low compression so you either get the benefit of running low octane fuel (less costly to operate) or the benefit of being able to run 8+psi through the thing.

Originally Posted by Randy WS6
Ive been running the aluminum LS2 block bored .030 over (4.030") for four years now and with a 350 shot of nitrous off the line at the track, and a lot of hard runs shifting a 7400 rpms,And street running. The LS2 is a very strong block, Im proof of that, and its still going strong, Im now starting a new build with the new LS3 aluminum block with it bored to.030" (4.095) = 431cid.

It took you a 350 shot to run 6.50's in the 1/8th... LOLs What are you running it in... a fuckin tank?

^^^^^
Now That's Funny LoL!

Originally Posted by Randy WS6
Ive been running the aluminum LS2 block bored .030 over (4.030") for four years now and with a 350 shot of nitrous off the line at the track, and a lot of hard runs shifting a 7400 rpms,And street running. The LS2 is a very strong block, Im proof of that, and its still going strong, Im now starting a new build with the new LS3 aluminum block with it bored to.030" (4.095) = 431cid.

It took you a 350 shot to run 6.50's in the 1/8th... LOLs What are you running it in... a fuckin tank?

^^^^^
Now That's Funny LoL!

No, the track time that i show, is with a 175 single shot on a 1/8 mile track. I run at a little track here that is 330 ft track that i was talking about with the 350 shot. I should have worded it differently. My car have full interior and AC. Ive had a lot of traction problem at the short track. Ill be going to the track in a few weeks and ill see what the time will be in a 1/8th on the 350 shot.

if 60-80lbs of weight (and block strength, mind you) really bothers you ... then you probably have other things to worry about before weight... mind you, the LQ4 and LY6 run really low compression so you either get the benefit of running low octane fuel (less costly to operate) or the benefit of being able to run 8+psi through the thing.

I would hope to think most of the people that are building an LQ4 dont give a damn about the stock internals, especially the pistons. I know I went with JE pistons with a -29cc valve relief.